Looks great so far!
SBD Dauntless, from scratch
- Thread starter Witold Jaworski
- Start date
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vikingBerserker
Lieutenant General
Nice!
- Thread starter
- #243
Witold Jaworski
Airman 1st Class
Wurger, Gnomey, vikingBerserker - thank you!
This week I continue mapping the SBD-5 Dauntless skin panels onto my model. After tracing the outer wing sections, described in the previous post, I traced the center wing section:
As you can see in the picture, I also traced the contours of the wheel bay on the wing surfaces. (These openings disappear, when you enter mesh edit mode, because they are dynamically created by Boolean modifiers. Thus such contours will be useful during further work, because in this way you can see these edges while editing the mesh).
I also outlined contours of the bomb bay panels, which are modeled separately "in the mesh" (every panel is a separate Blender object). I did it, because the panel lines that I draw on this image will be used as the input for various final textures. In some case I will use them as the source of "dirt" that occurs around every cleft in the aircraft skin. These thick lines will provide a decent effect on the textures.
Of course, I also used the reference photos to verify panel locations:
When I compared panel lines in the photo and my scale plans, I discovered that I have to make some corrections. There was a significant difference in the size of the fuel line covers (see figure above). In the real aircraft they were somewhat larger than on my drawings.
In similar way I mapped the empennage panels. The growing number of identified differences between the reference drawings and real airplane forced me to use these panel lines as a kind of additional reference picture. That's why I also decided to trace the ribs on all of the aircraft control surfaces.
Once I mapped these details, I started tracing fuselage panels. First I drew their "horizontal" lines that run along the longerons:
Fortunately, it was quite easy, because during the modeling phase I intentionally placed some edges of the fuselage mesh along rivet seams. Now this effort pays off.
Then I verified these new lines on the reference photo. I discovered that while the aileron and elevator ribs on the photo match my scale plans, the rudder ribs have different locations:
I also noticed another difference in the upper part of the tailplane fairing. Its outer edge runs along one of the fuselage longerons. In my model it is placed somewhat higher than in the photo:
When the other fuselage lines match their counterparts on the reference photo, this difference means an error in the shape of my model. I analyzed this area, and I started to suspect that the gap between the real line and line on my model is caused by the difference in the fairing shape. However, to be sure, I needed more evidence to proof this hypothesis. I carefully checked all available photos of this area:
Ultimately, I had found that the upper edge of the tailplane fairing is too high. In my model it overlaps the longeron line, while it should be adjacent to this panel seam. Lowering this edge will decrease the fillet radius in the upper area of the horizontal stabilizer fairing.
Well, it means that I have to revert to the modeling, and adjust the shape of this part:
I did most of the modifications shown in figure above by shifting mesh vertices along their edges. Fortunately, this command has an "update UVs" option, which automatically updates the mesh UV layout. Thus when I updated the fairing mesh and I looked on its UV map, the mesh was already updated there. I just had to export it to the reference image, and shift few lines into new location (as in figure "a", below):
After these modifications, fuselage panel lines match the photo (as in figure "b", above).
I had another kind of troubles with the lower part of the fuselage, behind the wing trailing edge. The UV layout of this mesh fragment has a significant distortion. A straight line on the model maps to a curve in this area. What's more, I had to split this area (using seams) into two separate parts, which also creates some continuity issues:
It was quite difficult to find a proper curve on the UV plane that transforms into a straight line on the model. This process required several iterations. After I managed to keep shapes of these lines within acceptable tolerance, I identified another difference between my model and the photos: a short seam below wing fairing trailing edge (see figure above). While in the real airplane it was a nearly straight line, in my model its rear part reproduces the conical shape of the trailing edge cross section. I suppose that this fuselage area had a visible deviation from the "ideal" conical shape, caused by the technological constrains. (It is difficult to apply such a more pronounced curvature, as you can see in my model, to the aircraft skin stringer). I will deal with this issue in the next post.
Figure below shows the complete set of the panel lines, mapped on the SBD-5 surface:
I still have to map the differences that occur in the other Dauntless versions (SBD-1, SBD-3). Frankly speaking, I started to note some variations in the layout of the fuselage panels between various restored SBDs. Sometimes it is difficult to distinguish the real, historical differences between various versions from the side-effects of a particular restoration.
In this source *.blend file you can evaluate yourself the current version of the model, and here is the Inkscape file.
This week I continue mapping the SBD-5 Dauntless skin panels onto my model. After tracing the outer wing sections, described in the previous post, I traced the center wing section:
As you can see in the picture, I also traced the contours of the wheel bay on the wing surfaces. (These openings disappear, when you enter mesh edit mode, because they are dynamically created by Boolean modifiers. Thus such contours will be useful during further work, because in this way you can see these edges while editing the mesh).
I also outlined contours of the bomb bay panels, which are modeled separately "in the mesh" (every panel is a separate Blender object). I did it, because the panel lines that I draw on this image will be used as the input for various final textures. In some case I will use them as the source of "dirt" that occurs around every cleft in the aircraft skin. These thick lines will provide a decent effect on the textures.
Of course, I also used the reference photos to verify panel locations:
When I compared panel lines in the photo and my scale plans, I discovered that I have to make some corrections. There was a significant difference in the size of the fuel line covers (see figure above). In the real aircraft they were somewhat larger than on my drawings.
In similar way I mapped the empennage panels. The growing number of identified differences between the reference drawings and real airplane forced me to use these panel lines as a kind of additional reference picture. That's why I also decided to trace the ribs on all of the aircraft control surfaces.
Once I mapped these details, I started tracing fuselage panels. First I drew their "horizontal" lines that run along the longerons:
Fortunately, it was quite easy, because during the modeling phase I intentionally placed some edges of the fuselage mesh along rivet seams. Now this effort pays off.
Then I verified these new lines on the reference photo. I discovered that while the aileron and elevator ribs on the photo match my scale plans, the rudder ribs have different locations:
I also noticed another difference in the upper part of the tailplane fairing. Its outer edge runs along one of the fuselage longerons. In my model it is placed somewhat higher than in the photo:
When the other fuselage lines match their counterparts on the reference photo, this difference means an error in the shape of my model. I analyzed this area, and I started to suspect that the gap between the real line and line on my model is caused by the difference in the fairing shape. However, to be sure, I needed more evidence to proof this hypothesis. I carefully checked all available photos of this area:
Ultimately, I had found that the upper edge of the tailplane fairing is too high. In my model it overlaps the longeron line, while it should be adjacent to this panel seam. Lowering this edge will decrease the fillet radius in the upper area of the horizontal stabilizer fairing.
Well, it means that I have to revert to the modeling, and adjust the shape of this part:
I did most of the modifications shown in figure above by shifting mesh vertices along their edges. Fortunately, this command has an "update UVs" option, which automatically updates the mesh UV layout. Thus when I updated the fairing mesh and I looked on its UV map, the mesh was already updated there. I just had to export it to the reference image, and shift few lines into new location (as in figure "a", below):
After these modifications, fuselage panel lines match the photo (as in figure "b", above).
I had another kind of troubles with the lower part of the fuselage, behind the wing trailing edge. The UV layout of this mesh fragment has a significant distortion. A straight line on the model maps to a curve in this area. What's more, I had to split this area (using seams) into two separate parts, which also creates some continuity issues:
It was quite difficult to find a proper curve on the UV plane that transforms into a straight line on the model. This process required several iterations. After I managed to keep shapes of these lines within acceptable tolerance, I identified another difference between my model and the photos: a short seam below wing fairing trailing edge (see figure above). While in the real airplane it was a nearly straight line, in my model its rear part reproduces the conical shape of the trailing edge cross section. I suppose that this fuselage area had a visible deviation from the "ideal" conical shape, caused by the technological constrains. (It is difficult to apply such a more pronounced curvature, as you can see in my model, to the aircraft skin stringer). I will deal with this issue in the next post.
Figure below shows the complete set of the panel lines, mapped on the SBD-5 surface:
I still have to map the differences that occur in the other Dauntless versions (SBD-1, SBD-3). Frankly speaking, I started to note some variations in the layout of the fuselage panels between various restored SBDs. Sometimes it is difficult to distinguish the real, historical differences between various versions from the side-effects of a particular restoration.
In this source *.blend file you can evaluate yourself the current version of the model, and here is the Inkscape file.
Lovely work so far!
- Thread starter
- #247
Witold Jaworski
Airman 1st Class
tomo pauk, Wurger, Gnomey - thank you!
This post is a small digression from the main thread – I will write here about a new method for recreating geometry of historical airplanes.
In one of my previous posts I complained that it is hard to find any reliable drawings of the historical propeller blades from the middle of 20th century. In particular, the geometry of various popular Hamilton Standard propellers from WWII era is unavailable. I have found in a discussion on one of the aviation forums that Hamilton Standard Company still keeps this data as their "business secret" – even their design from 1936!
So far, all we had were the photos *– but it is really difficult to precisely recreate from a few pictures such a twisted, complex shape as the propeller blade. However, it seems that there is a new hope! Two years ago I encountered on Blender Artists forum an interesting project. The Author of this thread (nick: NRK) used one of the general photo-based 3D scanning methods to obtain a spatial reference of a C-47 aircraft. Although this is not the SBD Dauntless, it seems that its Hamilton Standard propeller blades are similar to the blades used in the earlier Dauntless versions (SBD-1 .. SBD-3). Thus I asked NRK for the part of his 3D scan that contains the propeller. He sent me it within a few weeks (thank you very much, Nick!). Below you can see the picture of this blade and the contents of the 3D scan:
Note for the C-47 buffs: it seems that this aircraft used two different types of the Hamilton Standard blades. Most of the C-47s used wide-blade propellers, similar to those from the B-17 bombers. However, it seems that some of the C-47s used older, thin-blade propellers, which you can see in the aircraft from the picture above. For example, I have found similar blades in another C-47 from Commemorative Air Force, which was built in 1944.
NRK's 3D scan recreates only the upper (i.e. forward) propeller surface and its leading and trailing edge. However, it is still usable, because in most of the blades from this era their lower (i.e. rear) surface was flat. In this NACA report 642 (from 1937) I have found some tips about the airfoil used in the Hamilton Standard propellers: it could be R.A.F-6 or modified NACA-2400-34. Because the NACA-2400 had convex lower surface, I ultimately decided to use the R.A.F-6 airfoil:
R.A.F-6 is one of the pioneer airfoil shapes, designed in 1912. In that times engineers did most of the aircraft drawings with a chalk on the workshop floors. Thus the data points for this airfoil are relatively sparse, and leave some space for the handcraft – especially along the leading and trailing edges. I smoothed them using subdivision (i.e. B-spline) curves.
I connected this the R.A.F-6 airfoil to a circular base, creating in this way the initial segment of the propeller blade:
Then I fit this segment into the reference mesh:
As you can see on the picture above, the surface obtained from a 3D scan contains plenty of small irregularities. However, their presence helps to estimate the tolerance (i.e. the range of the shape deviations from the real surface) of this reference.
I formed the blade using the same methods as described in this post: by extruding and adjusting subsequent "ribs". First I recreated the general contour in the front view:
I formed the tip using the same methods as in this post: first I put an auxiliary circle (as an additional reference), then I connected the leading and trailing edges around this shape:
Then I rotated this blade a little, placing the tip surface on the reference surface:
At this moment the tip is the only fragment of the blade that fits the scanned surface: all the other blade segments are below or above it, because they are not twisted (yet).
I will twist this blade using curve modifier (as I did in this post). Thus I created such a curve:
Initially it was a straight line, placed on the blade axis (as in figure "a:, above). Simultaneously it lies on the rear (flat) blade surface (Because I placed all of the blade sections above its axis *– see the third figure in this post).
The blade of such a shape is not balanced – the centrifugal force would tore it off from the propeller hub. To avoid this effect, all blade cross-sections should have their centers placed on the blade axis. Thus in the side view the blade should resemble a symmetric triangle. I sketched its contours in figure "c", above) using white dashed lines. To fit the lower (rear) blade surface to such a line, I deflected the deforming curve downward (rotating it around the tip – as in figure "b", above). However, to simultaneously fit the blade upper surface to the top contour, I had to alter the thickness of its airfoils (see figures "c" and "d", above).
Figure below shows the resulting, "balanced" blade (it is still not twisted):
Finally, I twisted this blade by twisting subsequent vertices of its deforming curve. I did it until the leading and trailing edge fit their counterparts on the reference surface:
It was the last step of this process. You can find the resulting Hamilton Standard propeller blade in this source *.blend file.
Although it is still based on some assumptions (for example – the airfoil shape), this is much better approximation of the real shape than my previous attempts.
This post is a small digression from the main thread – I will write here about a new method for recreating geometry of historical airplanes.
In one of my previous posts I complained that it is hard to find any reliable drawings of the historical propeller blades from the middle of 20th century. In particular, the geometry of various popular Hamilton Standard propellers from WWII era is unavailable. I have found in a discussion on one of the aviation forums that Hamilton Standard Company still keeps this data as their "business secret" – even their design from 1936!
So far, all we had were the photos *– but it is really difficult to precisely recreate from a few pictures such a twisted, complex shape as the propeller blade. However, it seems that there is a new hope! Two years ago I encountered on Blender Artists forum an interesting project. The Author of this thread (nick: NRK) used one of the general photo-based 3D scanning methods to obtain a spatial reference of a C-47 aircraft. Although this is not the SBD Dauntless, it seems that its Hamilton Standard propeller blades are similar to the blades used in the earlier Dauntless versions (SBD-1 .. SBD-3). Thus I asked NRK for the part of his 3D scan that contains the propeller. He sent me it within a few weeks (thank you very much, Nick!). Below you can see the picture of this blade and the contents of the 3D scan:
Note for the C-47 buffs: it seems that this aircraft used two different types of the Hamilton Standard blades. Most of the C-47s used wide-blade propellers, similar to those from the B-17 bombers. However, it seems that some of the C-47s used older, thin-blade propellers, which you can see in the aircraft from the picture above. For example, I have found similar blades in another C-47 from Commemorative Air Force, which was built in 1944.
NRK's 3D scan recreates only the upper (i.e. forward) propeller surface and its leading and trailing edge. However, it is still usable, because in most of the blades from this era their lower (i.e. rear) surface was flat. In this NACA report 642 (from 1937) I have found some tips about the airfoil used in the Hamilton Standard propellers: it could be R.A.F-6 or modified NACA-2400-34. Because the NACA-2400 had convex lower surface, I ultimately decided to use the R.A.F-6 airfoil:
R.A.F-6 is one of the pioneer airfoil shapes, designed in 1912. In that times engineers did most of the aircraft drawings with a chalk on the workshop floors. Thus the data points for this airfoil are relatively sparse, and leave some space for the handcraft – especially along the leading and trailing edges. I smoothed them using subdivision (i.e. B-spline) curves.
I connected this the R.A.F-6 airfoil to a circular base, creating in this way the initial segment of the propeller blade:
Then I fit this segment into the reference mesh:
As you can see on the picture above, the surface obtained from a 3D scan contains plenty of small irregularities. However, their presence helps to estimate the tolerance (i.e. the range of the shape deviations from the real surface) of this reference.
I formed the blade using the same methods as described in this post: by extruding and adjusting subsequent "ribs". First I recreated the general contour in the front view:
I formed the tip using the same methods as in this post: first I put an auxiliary circle (as an additional reference), then I connected the leading and trailing edges around this shape:
Then I rotated this blade a little, placing the tip surface on the reference surface:
At this moment the tip is the only fragment of the blade that fits the scanned surface: all the other blade segments are below or above it, because they are not twisted (yet).
I will twist this blade using curve modifier (as I did in this post). Thus I created such a curve:
Initially it was a straight line, placed on the blade axis (as in figure "a:, above). Simultaneously it lies on the rear (flat) blade surface (Because I placed all of the blade sections above its axis *– see the third figure in this post).
The blade of such a shape is not balanced – the centrifugal force would tore it off from the propeller hub. To avoid this effect, all blade cross-sections should have their centers placed on the blade axis. Thus in the side view the blade should resemble a symmetric triangle. I sketched its contours in figure "c", above) using white dashed lines. To fit the lower (rear) blade surface to such a line, I deflected the deforming curve downward (rotating it around the tip – as in figure "b", above). However, to simultaneously fit the blade upper surface to the top contour, I had to alter the thickness of its airfoils (see figures "c" and "d", above).
Figure below shows the resulting, "balanced" blade (it is still not twisted):
Finally, I twisted this blade by twisting subsequent vertices of its deforming curve. I did it until the leading and trailing edge fit their counterparts on the reference surface:
It was the last step of this process. You can find the resulting Hamilton Standard propeller blade in this source *.blend file.
Although it is still based on some assumptions (for example – the airfoil shape), this is much better approximation of the real shape than my previous attempts.
Good work so far!
Lucky13
Forum Mascot
Fantastic work, as always!
- Thread starter
- #251
Witold Jaworski
Airman 1st Class
Wurger, Gnomey, Lucky13 - thank you for following!
In every creative process, after each "big step forward" you have to stop and carefully examine the results. Usually you have to make various corrections (sometimes minor, sometimes major), before taking the next step. This post describes such minor corrections that I had to make after mapping the key texture of the panel lines.
In my first post published in October, I drew the panel lines on the model, then compared them with the photos. Sometimes a minor difference between their layouts can lead to a discovery of an error in the fuselage shape. I in that post already found and fixed an issue in the shape of the tailplane fillet.
I also mentioned (see Figure 65‑9 in previous post) that I can see a difference in the bottom part of the wing fillet. Now I would like to resume my analysis at this point:
As you can see in the photo (figure "a", above) the shape of one of the seams on the bottom of the trailing edge (in red) differs from the photo (yellow dashed line). In my model this seam contains two segments figure "b", above): a straight line, corresponding to the flat, bottom surface of the fuselage, and a curved segment, resulting from the cross-section of the rounded trailing edge. From the geometrical point of view, such a shape is absolutely correct. However, it differs from the real airplane. Why?
Well, we should never forget about the way in which such an aircraft structure was built: there were fixed bulkheads of a fixed, determined shape, and the stringers (stiffeners) between them. It was possible to bend a little such a stringer between two subsequent bulkheads. However, the resulting curve always had a shape similar to a uniform, gentle arc – as you can see in the photo (figure "a", above). The combination of the straight segment and a curved segment (as in the model from figure "b", above) would require at least an additional bulkhead between these two segments. All in all, the real shape of the aircraft was not as ideal as you can see in my model. I had to modify its shape in this area.
Figure below shows the fuselage mesh before and after my modifications:
As you can see, in the final version I split the bottom of this fuselage into much more faces. It was one of these cases, when you try to change a single detail, then it occurs that this modification causes a "network effect". Initially I rearranged faces on the fillet trailing edge, creating two additional n-gons. It improved the shape of the seam line. However, this removed small crease edge that was "fixing" the deformation around seam corner. Thus I had to find another place for the seam… Well, the resulting mesh does not look especially elegant, but it finally creates the desired effect.
Figure "a", below, shows details of my new concept for unwrapping this area in the UV space. I had to reduce the low-distortion area behind the wing. Actually it is just large enough to contain the identification lights. (It would be extremely difficult to obtain their circular frames on the highly distorted faces "glued" to the main part of the fuselage):
Figure "b", above, shows the modified UV layout of the fuselage mesh. This time I was able to not break any of the panel seam lines in the middle. Actually the new UV seam crosses just a single rivet line. (It does not create as many further complications as in the case of the crossed panel line).
Below you can see the panel lines on the updated model:
After so many modifications applied to the fuselage mesh, it is a good idea to check if they did not spoil something in the alternate UV layout. (This is second UV layout in this model. As you can find in the previous posts, I created the first UV layout, named UVMap, for the other textures, for example – for the camouflage).
Indeed, when I switched the current UV layout from UVTech to UVMap, I saw that I have some troubles here:
The primary reasons of these troubles are:
To fix this flaw, I modified the UVMap layout. I had to accept that there will be some distortion of the texture image on the bottom wing fillet areas, as you can see in figures "a" and "c", below. I decided that such a distortion is passable for the color textures (for the technical details I will use another, UVTech layout).
An important element of the UV layout for color textures is the location of the seam lines. (The unavoidable color differences between separate parts of the texture image always occur along the UV layout seams). Usually I try to hide them, marking as the UV seams the mesh edges that run along a panel seam (see Figure 60-2, in this post). That's why I cannot use here the seams from the UVTech texture: they run across a "blank" area of the aircraft skin. However, there are no appropriate panel seams in this area. Thus I when I decided to create an additional seam, I placed it along one of the rivet seams (as in figure "a", below):
Then I had to modify the layout of the mesh faces in the UV space (figure "b", above). (I used a little Blender trick to quickly obtain such an effect. First I temporarily removed the seams from the alternate UVTech map. I also removed all the "pins" from the vertices around this seam. Then I invoked the "Unwrap" command, and all the mesh faces "reorganized" themselves around the new seam. Finally I had just to pin them again, and restore the removed seams from the other mappings.)
However, it seems that I went in my modifications too far, when I "improved" the upper part of the wing fillet:
I deformed its original, conic shape, unconsciously reducing the cross-section radii of this surface over the wing upper area. It seems that I had forgotten to look on the photos. Now I have to fix this error.
To ensure that the shape of the panel lines in my model will match the photo, I placed in the model space some auxiliary "stiffeners" (figure 'a", below):
The reference photos were a great help here: some of them depicted these stiffeners in the side view, the others – in the top view (figure "b", above). I used these pictures to precisely determine locations of these seams in the 3D space.
Using my auxiliary objects, I was able to recreate the wing fillet with greater precision:
As you can see in the figure above, I also created two auxiliary conical segments. They provide me a kind of "indicator" of the differences between the "ideal shape" and the fuselage surface.
Figure below shows the results. Because there are no panel seams along the inner stiffeners of the wing fillet, I drew their rivet seams on the model texture. As you can see, they match both reference photos:
In this source *.blend file you can evaluate yourself the current version of the model, and here is the Inkscape file.
Within two-three weeks I should prepare the first texture. It will be the bump map.
In every creative process, after each "big step forward" you have to stop and carefully examine the results. Usually you have to make various corrections (sometimes minor, sometimes major), before taking the next step. This post describes such minor corrections that I had to make after mapping the key texture of the panel lines.
In my first post published in October, I drew the panel lines on the model, then compared them with the photos. Sometimes a minor difference between their layouts can lead to a discovery of an error in the fuselage shape. I in that post already found and fixed an issue in the shape of the tailplane fillet.
I also mentioned (see Figure 65‑9 in previous post) that I can see a difference in the bottom part of the wing fillet. Now I would like to resume my analysis at this point:
As you can see in the photo (figure "a", above) the shape of one of the seams on the bottom of the trailing edge (in red) differs from the photo (yellow dashed line). In my model this seam contains two segments figure "b", above): a straight line, corresponding to the flat, bottom surface of the fuselage, and a curved segment, resulting from the cross-section of the rounded trailing edge. From the geometrical point of view, such a shape is absolutely correct. However, it differs from the real airplane. Why?
Well, we should never forget about the way in which such an aircraft structure was built: there were fixed bulkheads of a fixed, determined shape, and the stringers (stiffeners) between them. It was possible to bend a little such a stringer between two subsequent bulkheads. However, the resulting curve always had a shape similar to a uniform, gentle arc – as you can see in the photo (figure "a", above). The combination of the straight segment and a curved segment (as in the model from figure "b", above) would require at least an additional bulkhead between these two segments. All in all, the real shape of the aircraft was not as ideal as you can see in my model. I had to modify its shape in this area.
Figure below shows the fuselage mesh before and after my modifications:
As you can see, in the final version I split the bottom of this fuselage into much more faces. It was one of these cases, when you try to change a single detail, then it occurs that this modification causes a "network effect". Initially I rearranged faces on the fillet trailing edge, creating two additional n-gons. It improved the shape of the seam line. However, this removed small crease edge that was "fixing" the deformation around seam corner. Thus I had to find another place for the seam… Well, the resulting mesh does not look especially elegant, but it finally creates the desired effect.
Figure "a", below, shows details of my new concept for unwrapping this area in the UV space. I had to reduce the low-distortion area behind the wing. Actually it is just large enough to contain the identification lights. (It would be extremely difficult to obtain their circular frames on the highly distorted faces "glued" to the main part of the fuselage):
Figure "b", above, shows the modified UV layout of the fuselage mesh. This time I was able to not break any of the panel seam lines in the middle. Actually the new UV seam crosses just a single rivet line. (It does not create as many further complications as in the case of the crossed panel line).
Below you can see the panel lines on the updated model:
After so many modifications applied to the fuselage mesh, it is a good idea to check if they did not spoil something in the alternate UV layout. (This is second UV layout in this model. As you can find in the previous posts, I created the first UV layout, named UVMap, for the other textures, for example – for the camouflage).
Indeed, when I switched the current UV layout from UVTech to UVMap, I saw that I have some troubles here:
The primary reasons of these troubles are:
- Substantial modification of the mesh topology in this area (some of the original faces that were mapped in this layout have disappeared);
- Alteration of the seam line: seam lines are shared between UV layouts. I altered the original seam to another edge loop, while working on the UVTech layout;
To fix this flaw, I modified the UVMap layout. I had to accept that there will be some distortion of the texture image on the bottom wing fillet areas, as you can see in figures "a" and "c", below. I decided that such a distortion is passable for the color textures (for the technical details I will use another, UVTech layout).
An important element of the UV layout for color textures is the location of the seam lines. (The unavoidable color differences between separate parts of the texture image always occur along the UV layout seams). Usually I try to hide them, marking as the UV seams the mesh edges that run along a panel seam (see Figure 60-2, in this post). That's why I cannot use here the seams from the UVTech texture: they run across a "blank" area of the aircraft skin. However, there are no appropriate panel seams in this area. Thus I when I decided to create an additional seam, I placed it along one of the rivet seams (as in figure "a", below):
Then I had to modify the layout of the mesh faces in the UV space (figure "b", above). (I used a little Blender trick to quickly obtain such an effect. First I temporarily removed the seams from the alternate UVTech map. I also removed all the "pins" from the vertices around this seam. Then I invoked the "Unwrap" command, and all the mesh faces "reorganized" themselves around the new seam. Finally I had just to pin them again, and restore the removed seams from the other mappings.)
However, it seems that I went in my modifications too far, when I "improved" the upper part of the wing fillet:
I deformed its original, conic shape, unconsciously reducing the cross-section radii of this surface over the wing upper area. It seems that I had forgotten to look on the photos. Now I have to fix this error.
To ensure that the shape of the panel lines in my model will match the photo, I placed in the model space some auxiliary "stiffeners" (figure 'a", below):
The reference photos were a great help here: some of them depicted these stiffeners in the side view, the others – in the top view (figure "b", above). I used these pictures to precisely determine locations of these seams in the 3D space.
Using my auxiliary objects, I was able to recreate the wing fillet with greater precision:
As you can see in the figure above, I also created two auxiliary conical segments. They provide me a kind of "indicator" of the differences between the "ideal shape" and the fuselage surface.
Figure below shows the results. Because there are no panel seams along the inner stiffeners of the wing fillet, I drew their rivet seams on the model texture. As you can see, they match both reference photos:
In this source *.blend file you can evaluate yourself the current version of the model, and here is the Inkscape file.
Within two-three weeks I should prepare the first texture. It will be the bump map.
Looks great so far!
vikingBerserker
Lieutenant General
Man, that is just impressive!
Robert Porter
Senior Master Sergeant
Wow! Impressive effort and skills! I am nowhere near that skilled yet, if ever, but I can certainly admire the effort it took!
- Thread starter
- #256
Witold Jaworski
Airman 1st Class
Wurger, Gnomey, vikingBerserker, Robert Porter - thank you for following!
Since November I am engaged in a time-consuming project in my daily job.
I will resume my work on this model in March 2017.
Since November I am engaged in a time-consuming project in my daily job.
I will resume my work on this model in March 2017.
SANCER
Senior Master Sergeant
IMPRESSIVE WORK AND DOMAIN OF THE IMAGES AND DIAGRAMS !!!
I had never seen such magnitude of detail, work and perfection !!
I have no more to congratulate you!! =D>
Estoy impresionado!!!
Saludos Maestro!
I had never seen such magnitude of detail, work and perfection !!
I have no more to congratulate you!! =D>
Estoy impresionado!!!
Saludos Maestro!
- Thread starter
- #258
Witold Jaworski
Airman 1st Class
SANCER - muchas gracias! 
OK, I successfully completed in March my "daily" project, so I am back at my work here.
In this and the next post I will describe my work on the first of the textures required for the SBD Dauntless model. It is called bump (height) map. I use it for recreating all of the minor details that are visible on the aircraft skin.
However, before I begin this work, I had to put my model into more "natural" surroundings. I imported the environment (World) and the material settings from my previous model (the P-40). You can see the initial results below:
Of course, the propeller of this aircraft is static, and there is nothing in the cockpit and under the engine cowling. Do not worry, this is just the first approximation! The principle is that you should work with the materials in the final environment. Otherwise the final result may not look as you want. In this case there is an outdoor scene, full of the sunlight. (Every painter will tell you, that everything on the picture depends on the light: many details would look quite different in the indoor lights and their soft shadows).
As you can see, I decided to start this work with an ideal, smooth and shiny material. Each new texture that I will apply will make it more realistic.
Note for those, who will examine the contents of the Blender file that accompanies this post: I am using the Cycles renderer to create this one and the future pictures. (Cycles is one of the Blender rendering engines). The node-based schemas of its environment and materials are quite complex. What's more, I modified them after importing from my P-40 model, temporarily removing all of the original P-40 textures, and disconnecting many fragments that initially are not needed:
If you would like to analyze details of this setup – you can find its step-by-step description in vol. III of the "Virtual Airplane" guide. It shows how to obtain the required effects, and also discusses some of the possible alternatives.
Creation of the bump map resembles work on a new scale plan. I am drawing it as the scalable (vector) drawing in Inkscape, adding new details to the picture that I started in one of the previous posts. Keeping the source picture of this texture in the SVG format allows me to quickly generate image of any resolution.
I decided that it will be much easier to use the same texture for all of the SBD versions. Thus I had to shift the UV maps of some version-specific elements (mainly the engine cowlings) into the other, unused areas of this UV space.
Then I had to fill the areas between the panel lines with rivet seams, bolts and various inspection doors. I stared with the center wing area. I used the reference drawings (scale plans and the UV mesh layouts) to create the first approximation of these lines:
Technically, I sketched the rivet seams as dotted lines, using a customized dot pattern. (You can find how to do it in the "Virtual Airplane" guide, in the chapter about Inkscape, section titled "Drawing a dotted line (rivets)").
Then I matched these seams against the reference photo. Initially these rivets were in red, because this color makes them more visible against the background picture:
During this work I had both: Blender and Inkscape windows on my screen, side-by-side. On the reference photo in Blender I could see the differences between the real rivet seams and my drawing. Using these findings, I updated accordingly the drawing in Inkscape. Then I exported it from Inkscape as a new version of the *.png file, reloaded it in Blender, and looked for the remaining differences. Refreshing the mapped image with these "export+reload" commands is quick and requires just two mouse clicks, and one keyboard shortcut in Blender. Usually I need between 3 and 6 of such iterations to obtain a satisfactory match between my drawing and the photo of the given part of the aircraft.
When the rivet seams are in place, it is good idea to check if the internal ribs and spars fit their lines. (While working on the wing, I created a few of these internal reinforcements inside the wheel bay *– see figure below):
In the 3D View mode Blender draws the texture on both sides of the surface, so such a comparison is pretty straightforward. To see the rivet seams "through" the elements being verified, I switched their display mode to Wire. When I identified a difference, the rule was that the rivet seams are in proper location (because they were already verified against the reference photos, while these ribs and spars were based just on the reference drawing). In the case depicted above, I had to move forward the front spar (by less than 0.5").
When I verified all the rivet seams from the current area, I switched their colors. Because the leading edge of the SBD wing had smooth finish with flush rivets, I created for them new sublayer, named Flush. These seam lines are black. The remaining rivets had classic (dome) heads, thus they are white. I placed them on another sublayer named Dome. I also added to this drawing the inspection doors and the fuel filler cover:
In the bump map texture, the shade of the gray determines the height of an area. The highest element is white, while the lowest is black. Thus I switched the background color of my Inkscape drawing to the neutral gray (50% black + 50% white). Then I could recreate the aircraft skin panels. In the SBD Dauntless these panels overlapped each other. To achieve this effect, I used areas filled with linear gradient:
In this fragment of the aircraft skin I used only areas filled with vertical gradients. I placed them on Panels:Vertical sublayer. (In more general cases, I will also use another set of panels, from :Horizontal sublayer). There are always some sheets riveted atop other panels. In this drawing, I drawn them as the lightest areas, placed on Overlays layer. To decrease variation of the rivets height between the darker and lighter areas, I made their layers partially transparent. (See more details of this method in the "Virtual Airplane" guide, in the chapter about Inkscape, section titled "Mapping construction details of airplane surfaces").
As you can see in the figure above, I also sketched various minor openings in the aircraft skin. Initially they are red (just for easier matching against the reference photos). Ultimately the verified elements from this layer are black. I will use them not only for the bump map, but also for another auxiliary texture: the opacity map (you will see it "in action", soon).
OK, let's check how this first fragment of the bump map looks on the model. I exported it from Inkscape as a raster image (4096x4096px) named nor_details.png. Then I added to the material schema an Image Texture node, which represents this image. It is connected to the Displacement slot in the material output:
As you can see in the figure above, I selected one of the available UV maps by name *– using the Attribute node. Usually in my schemes it is accompanied by a UV Fallback node. This custom (group) node provides the default UV map for the meshes that do not have the UV map specified in the Attribute node.
You can evaluate the results below:
The first thing that I noticed: the dark gray dots that I used to emulate the flush rivets should create less visible seams. Currently their rivets seems too deep – so I should make these dots lighter. The same applies to the small bumps around bolt heads (visible on the covers).
You can see the details created by the bump texture when you place the model between the camera and the sunlight. (Check it, playing with the rendered model that accompanies this post). These skin details can completely disappear, when you look at the model from certain directions. As in the real world, all these rivets and panel seams are mostly visible not because of their shape (recreated by the bump map), but because of the small amounts of dust and dirt that accumulate around them. In one of the future posts I will recreate this effect, using the reflectivity texture. For this purpose I will reuse most layers from the bump map image.
In this source *.blend file you can evaluate yourself the current version of the model.
As you can see in this post, you have to draw a lot of details while preparing the bump map. (I think that this is the most time-consuming texture). However, nearly all of the other textures will base its drawing. In the next post I am going to show you the finished version, so give me some time to complete its image. I think that I will publish this second article about bump map within two weeks (on April 8th).
OK, I successfully completed in March my "daily" project, so I am back at my work here.
In this and the next post I will describe my work on the first of the textures required for the SBD Dauntless model. It is called bump (height) map. I use it for recreating all of the minor details that are visible on the aircraft skin.
However, before I begin this work, I had to put my model into more "natural" surroundings. I imported the environment (World) and the material settings from my previous model (the P-40). You can see the initial results below:
Of course, the propeller of this aircraft is static, and there is nothing in the cockpit and under the engine cowling. Do not worry, this is just the first approximation! The principle is that you should work with the materials in the final environment. Otherwise the final result may not look as you want. In this case there is an outdoor scene, full of the sunlight. (Every painter will tell you, that everything on the picture depends on the light: many details would look quite different in the indoor lights and their soft shadows).
As you can see, I decided to start this work with an ideal, smooth and shiny material. Each new texture that I will apply will make it more realistic.
Note for those, who will examine the contents of the Blender file that accompanies this post: I am using the Cycles renderer to create this one and the future pictures. (Cycles is one of the Blender rendering engines). The node-based schemas of its environment and materials are quite complex. What's more, I modified them after importing from my P-40 model, temporarily removing all of the original P-40 textures, and disconnecting many fragments that initially are not needed:
If you would like to analyze details of this setup – you can find its step-by-step description in vol. III of the "Virtual Airplane" guide. It shows how to obtain the required effects, and also discusses some of the possible alternatives.
Creation of the bump map resembles work on a new scale plan. I am drawing it as the scalable (vector) drawing in Inkscape, adding new details to the picture that I started in one of the previous posts. Keeping the source picture of this texture in the SVG format allows me to quickly generate image of any resolution.
I decided that it will be much easier to use the same texture for all of the SBD versions. Thus I had to shift the UV maps of some version-specific elements (mainly the engine cowlings) into the other, unused areas of this UV space.
Then I had to fill the areas between the panel lines with rivet seams, bolts and various inspection doors. I stared with the center wing area. I used the reference drawings (scale plans and the UV mesh layouts) to create the first approximation of these lines:
Technically, I sketched the rivet seams as dotted lines, using a customized dot pattern. (You can find how to do it in the "Virtual Airplane" guide, in the chapter about Inkscape, section titled "Drawing a dotted line (rivets)").
Then I matched these seams against the reference photo. Initially these rivets were in red, because this color makes them more visible against the background picture:
During this work I had both: Blender and Inkscape windows on my screen, side-by-side. On the reference photo in Blender I could see the differences between the real rivet seams and my drawing. Using these findings, I updated accordingly the drawing in Inkscape. Then I exported it from Inkscape as a new version of the *.png file, reloaded it in Blender, and looked for the remaining differences. Refreshing the mapped image with these "export+reload" commands is quick and requires just two mouse clicks, and one keyboard shortcut in Blender. Usually I need between 3 and 6 of such iterations to obtain a satisfactory match between my drawing and the photo of the given part of the aircraft.
When the rivet seams are in place, it is good idea to check if the internal ribs and spars fit their lines. (While working on the wing, I created a few of these internal reinforcements inside the wheel bay *– see figure below):
In the 3D View mode Blender draws the texture on both sides of the surface, so such a comparison is pretty straightforward. To see the rivet seams "through" the elements being verified, I switched their display mode to Wire. When I identified a difference, the rule was that the rivet seams are in proper location (because they were already verified against the reference photos, while these ribs and spars were based just on the reference drawing). In the case depicted above, I had to move forward the front spar (by less than 0.5").
When I verified all the rivet seams from the current area, I switched their colors. Because the leading edge of the SBD wing had smooth finish with flush rivets, I created for them new sublayer, named Flush. These seam lines are black. The remaining rivets had classic (dome) heads, thus they are white. I placed them on another sublayer named Dome. I also added to this drawing the inspection doors and the fuel filler cover:
In the bump map texture, the shade of the gray determines the height of an area. The highest element is white, while the lowest is black. Thus I switched the background color of my Inkscape drawing to the neutral gray (50% black + 50% white). Then I could recreate the aircraft skin panels. In the SBD Dauntless these panels overlapped each other. To achieve this effect, I used areas filled with linear gradient:
In this fragment of the aircraft skin I used only areas filled with vertical gradients. I placed them on Panels:Vertical sublayer. (In more general cases, I will also use another set of panels, from :Horizontal sublayer). There are always some sheets riveted atop other panels. In this drawing, I drawn them as the lightest areas, placed on Overlays layer. To decrease variation of the rivets height between the darker and lighter areas, I made their layers partially transparent. (See more details of this method in the "Virtual Airplane" guide, in the chapter about Inkscape, section titled "Mapping construction details of airplane surfaces").
As you can see in the figure above, I also sketched various minor openings in the aircraft skin. Initially they are red (just for easier matching against the reference photos). Ultimately the verified elements from this layer are black. I will use them not only for the bump map, but also for another auxiliary texture: the opacity map (you will see it "in action", soon).
OK, let's check how this first fragment of the bump map looks on the model. I exported it from Inkscape as a raster image (4096x4096px) named nor_details.png. Then I added to the material schema an Image Texture node, which represents this image. It is connected to the Displacement slot in the material output:
As you can see in the figure above, I selected one of the available UV maps by name *– using the Attribute node. Usually in my schemes it is accompanied by a UV Fallback node. This custom (group) node provides the default UV map for the meshes that do not have the UV map specified in the Attribute node.
You can evaluate the results below:
The first thing that I noticed: the dark gray dots that I used to emulate the flush rivets should create less visible seams. Currently their rivets seems too deep – so I should make these dots lighter. The same applies to the small bumps around bolt heads (visible on the covers).
You can see the details created by the bump texture when you place the model between the camera and the sunlight. (Check it, playing with the rendered model that accompanies this post). These skin details can completely disappear, when you look at the model from certain directions. As in the real world, all these rivets and panel seams are mostly visible not because of their shape (recreated by the bump map), but because of the small amounts of dust and dirt that accumulate around them. In one of the future posts I will recreate this effect, using the reflectivity texture. For this purpose I will reuse most layers from the bump map image.
In this source *.blend file you can evaluate yourself the current version of the model.
As you can see in this post, you have to draw a lot of details while preparing the bump map. (I think that this is the most time-consuming texture). However, nearly all of the other textures will base its drawing. In the next post I am going to show you the finished version, so give me some time to complete its image. I think that I will publish this second article about bump map within two weeks (on April 8th).
Lucky13
Forum Mascot
Agree with Wojtek!
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