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Texture baking question
Old 03-31-2010, 10:19 AM   #1
jackalennui
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Crossposted from SLU in the hope that someone here might have some good tips for me.

---

I hope this question will make sense and not seem totally whacky .. when it comes to 3d I'm entirely self-taught. I'm using modo but since it's a rather general question I'd love to read your input, no matter what app(s) you use for 3d.

When I bake a texture for a sculptie, the specular highlights, shadows etc. are computed and baked from the camera's position at the time of the bake. So, for instance, I set up my scene with a shoe (I'll take a shoe as example as that's what I'm mostly building); global illumination; the camera looking towards the toes from the front, off to one side, and a bit from above; one directional light set up like the camera and another one off to the other side. Then when I bake the texture, I only get specular highlights on one side of the shoe (where the camera was looking to) and the heel has mostly flat color and possibly some AO shadows but not highlights.

It makes sense that it would turn out that way, as the highlights are calculated relatively to the camera, and the cam does of course not see the heel, only the toes. But I have seen baked shoes with highlights on both sides of the toes, or with the heel having highlights and shadows too, and I'm kind of puzzled at this point.

- do they bake the texture from various camera positions and composite it in Photoshop?
- or is it possible to do a bake from 2/3/4 camera positions and have the 3d app composite that itself?
- or was I only seeing ambient occlusion with some manual postprocessing for color and highlights in Photoshop?

I would appreciate any tips and pointers on that subject, and if I'm totally off with what I'm doing please refer me to good tutorials! I have read "Digital lighting and rendering" and while it was very helpful it's not a very technical book, and I guess I'm really looking for more technical help here.
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Old 03-31-2010, 10:47 AM   #2
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zbrush can use a plugin called 'material baker' that will move the cam around baking and then gives you what youre wanting. i imagine there are ways to do it with modo.
Quote:
Originally Posted by jackalennui View Post
Crossposted from SLU in the hope that someone here might have some good tips for me.

---

I hope this question will make sense and not seem totally whacky .. when it comes to 3d I'm entirely self-taught. I'm using modo but since it's a rather general question I'd love to read your input, no matter what app(s) you use for 3d.

When I bake a texture for a sculptie, the specular highlights, shadows etc. are computed and baked from the camera's position at the time of the bake. So, for instance, I set up my scene with a shoe (I'll take a shoe as example as that's what I'm mostly building); global illumination; the camera looking towards the toes from the front, off to one side, and a bit from above; one directional light set up like the camera and another one off to the other side. Then when I bake the texture, I only get specular highlights on one side of the shoe (where the camera was looking to) and the heel has mostly flat color and possibly some AO shadows but not highlights.

It makes sense that it would turn out that way, as the highlights are calculated relatively to the camera, and the cam does of course not see the heel, only the toes. But I have seen baked shoes with highlights on both sides of the toes, or with the heel having highlights and shadows too, and I'm kind of puzzled at this point.

- do they bake the texture from various camera positions and composite it in Photoshop?
- or is it possible to do a bake from 2/3/4 camera positions and have the 3d app composite that itself?
- or was I only seeing ambient occlusion with some manual postprocessing for color and highlights in Photoshop?

I would appreciate any tips and pointers on that subject, and if I'm totally off with what I'm doing please refer me to good tutorials! I have read "Digital lighting and rendering" and while it was very helpful it's not a very technical book, and I guess I'm really looking for more technical help here.
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Old 03-31-2010, 06:35 PM   #3
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Quote:
Originally Posted by jackalennui View Post
Techy stuff.
I don't know the program you are using, but, camera view would only bake what view your camera sees, hence why you are not getting specularity all around your shoes. I use Maya with mental ray and the turtle plug in, depends what i am trying to do.

if there is an option try baking in the perspective view with orthographic reflection checked off, if you have this.

Another reason, you may not have enough lights set up. Stay away from Ambient lights when trying to capture specularity. Ambient lighting will drown out any specularity.

Your lighting is so important and the hardest part of texture baking as you know. unlike , lets say a couch, you dont need as much light in the back. Depending on what i am trying to achieve, i can use up to 8 - 10 lights on a single shoe. Each having their own fade off, intensity and raytrace.

Point lights and spot lights are also useful, Directional lights, you don't have as much fine tune control.

As for PS, you can clean up your final bake/light map and do the remaining texturing in PS. I don't bake textures right on the model anymore. I have more control in PS. The light maps are baked, umm 50 million times until i get it right.

ETA: sometimes the simplest thing will solve the problem. Try changing your camera and your lighting set up. I know in maya you have surface front, surface back. This has to do with the outside of the mesh and inside of the mesh. Once i understood this, it solved my frustration with baking.
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Old 03-31-2010, 06:42 PM   #4
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The simplest explanation is probably the best.
I would tend to think the shoes you were seeing were not rendered with super complicated rigs and settings, but maybe someone put a light just on the heel, and told it to ignore the rest of the shoe.
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Old 03-31-2010, 08:15 PM   #5
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Tya, thank you so much for your input. You've given me enough pointers to keep me busy for weeks! and now at least I know what I'm looking for.
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Old 03-31-2010, 08:59 PM   #6
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if you could send me a screenshot of your texture bake options, i will take a look at it and see what the right setting is for you, as the language might be a different from maya

tyafsl@gmail.com

oh just to add, global illumination is a total diff ball game, i would pin down without GI why you are only baking on one side first. it will cut out some frustration.

Lighting in any 3d program runs the same principal as photography lighting, the 3 light set up. This is your base set up. From there you add lights to get what you need.

When baking with shadows, you have to be careful. On a shoe, trust me, it can make your textures over dark, to spread out .Turn off shadows for now and just work with the basic light and perspective view.
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Old 04-09-2010, 05:27 AM   #7
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I'm not particularly familiar with Modo, but the codebase is related to Lightwave, so what I say should be more or less true.

When baking from the camera's POV the polygon orientation becomes important - some of the polys will have their "backs" to the camera and, if you're not using a double sided surface, they'll get culled by the renderer and won't appear in the baked texture.

The options for fixing this are to use a double sided surface, double up the polys with flipped copies, or to use a baking orientation that doesn't depend on the camera or a fixed position. There should be an option somewhere to bake from a normal to the surface - in this way the "camera" travels across the surface during the baking and polygon orientation isn't so important.
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