0
\$\begingroup\$

I have an obj mesh with some textures, several of them are repeated(uvs are not within [0,1]). I'd like to merge all those textures into one texture and transform the uvs of obj.

\$\endgroup\$
  • 2
    \$\begingroup\$ Have you considered using an Array Texture, so you can keep your wrapping UVs mostly as-is? \$\endgroup\$ – DMGregory Dec 5 '18 at 18:04
  • \$\begingroup\$ Texture arrays are certainly the way to go but have restrictions in dx11. You can't have textures of varying size in the array although dx 12 you can. \$\endgroup\$ – ErnieDingo Jan 5 at 3:58
1
\$\begingroup\$

Since the question is about "efficiently" packing a mix of repeated and non-repeated textures into a texture atlas, the answer is: most likely no, you can't. As DMGregory said Texture Arrays are probably the way to go instead.

Why:

If you want to go the atlas way you will have to slice triangles on UV repeat edges (edges in texture space) but this may significantly increase your mesh complexity, increasing geometry workload.

And this has repercussions for linear interpolation, including mip-maps.

This means you'll need to add a repeated border at least 2^(n+1) pixels thick where n is the number of mip-map levels you want.

Unless you're making a voxel engine or GUI engine that would otherwise cause massive amount of texture switches there isn't a gain to be had. As long as the GPU can handle the number of textures being sampled in a single object there isn't a real benefit to creating an atlas.

At the shader level sampling 4 different texture or sampling a single texture atlas 4 times makes no difference to a modern GPU of at least the last 10 years.

The only saving might be the removal of 3 tiny "Set Texture Sampler {X} to Texture {Y}" commands from the GPU command stream.

If you gain any benefit at all from this you will likely gain a higher benefit by making sure all your objects using the same material are rendered at once without switching materials / GPU render states. Making the atlas packing gains insignificant.

Large texture atlases also prevent some GPUs from efficiently managing GPU RAM as some need to transfer entire textures to GPU RAM before running the shader.

So while automatically-generated texture atlases make sense for GUI text or 2D tile / 3D voxel massively-tile-based renderer, it does not make so much sense for characters.

The usual way to go is to bake (combine) the complex textures layers into simpler unwrapped textures using a capable 3D modeling/painting software.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.