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Old 06-13-2013, 09:52 PM
dproeder dproeder is offline
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Join Date: May 2013
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Lightbulb Demystifying exporting light maps from 3ds Max to Vizard?

Hey all.

So when following the steps in the Vizard documentation on baking and exporting light maps from 3ds Max I started wondering about a few things. I am an experienced Maya and Unity User so I kinda wanted to know whats being generated and whats being exported during this process.


Is 3ds Max creating a 2nd UV set with automatically laid UVs with a monochromatic light map?

Is 3ds max overwriting your current UVs and baking the lighting information directly onto your diffuse?

When you export the newly light baked models from Max to Vizard, what is being transfered?
Is it 2 separate maps such as a Light Map and your original Diffuse?
Is it 1 map with lighting baked directly into your diffuse?

How does vizard process this lighting information? When exporting with "lighting turned off", does vizard have any light source in its scenes? Are the light sources read from the exported lighting information from the osgb?


I am not a fan of 3ds Max's scene management. It is very difficult to work in a scene with many objects and a million+ triangle count. I would rather bake lighting in Maya and transfer over the baked meshes to 3ds Max in FBX form. Knowing how Vizard reads light map information will help me create this workflow.

Thanks from IVC Greenville!
-patrick
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Old 06-14-2013, 01:34 PM
Veleno Veleno is offline
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Join Date: Sep 2005
Posts: 148
Hi Patrick,

Quote:
Is 3ds Max creating a 2nd UV set with automatically laid UVs with a monochromatic light map?
Generally yes, but it's also possible to use a manually created channel or modify the automatic unwrap result.

Quote:
Is 3ds max overwriting your current UVs and baking the lighting information directly onto your diffuse?
The automatic unwrap defaults to channel 3, but this can be changed before unwrapping. The workflow we typically use for our own projects assumes baking will be done at some point, so we reserve channel 3 for that use.

Quote:
When you export the newly light baked models from Max to Vizard, what is being transferred?
Is it 2 separate maps such as a Light Map and your original Diffuse?
Is it 1 map with lighting baked directly into your diffuse?
Both are possible. We define LightMaps as containing only the lighting. The latter case is what Max calls a CompleteMap. When baked with a good renderer (e.g. VRay) CompleteMaps give the most photorealistic result that can come from a static map, but the memory overhead is high and maintaining close-up detail becomes impossible on larger scenes. LightMaps are much more versatile since diffuse maps to be tiled separately (making close-up detail a non-issue), and have significantly less memory overhead, but the combined result won't look as photo-real.

Quote:
How does vizard process this lighting information? When exporting with "lighting turned off", does vizard have any light source in its scenes? Are the light sources read from the exported lighting information from the osgb?
"Turn off lighting" disables real-time lighting on a model and displays the textures exactly as they appear in the file.

Vizard R4 uses the OpenGL Fixed Function Pipeline shader, which is fairly simplistic in the way it handles maps (and lighting). In short, the FFP has no knowledge of what most maps are actually meant to do and simply multiplies the values against each other, sometimes with a scale factor applied (lightmap scale option in the exporter, 2x recommended). This works very well for combining lightmaps with diffuse maps (lighting hitting the surface * the diffuse reflectance of the surface = final brightness), but the use of things like specular maps require fragment shaders. GLSL fragment shaders are possible in R4 but must supplied by the user. This will no longer be an issue in R5.
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3ds max, light baking, maya, osgb export, uv sets

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