Batched GPU Directional Sprite testing on texture atlas

Trying to use GPU to automatically determine sprite angle and modify the V coordinate accordingly. (U coordinate is for animation frame). I think using GPU to determine this has disadvantages since it's 4x more work to the GPU per vertex (and uploading 1 more vertex constant, ie. the facing direction of sprite to the GPU, resulting in lower batch count). But, you won't need to manually check/update the angle UV frames for each sprite on the CPU. I could always fall back to a basic TextureAtlasMaterial and manually supply the UV coordinates for each sprite in SpriteSet's data array, if required.

Sprites from Daggerfall.

Away3D alreadyhas a built-in spritesheet animation system/utility and tutorial.
http://away3d.com/tutorials/Using_sprite_sheets_in_your_project
In alternativa3d, you would have to come up with your own custom solution/materials/tools like what is done here.