Hi everyone,

Houdini 16.5.323
Game Development Toolset 1.9

I'm having an issue where the alpha is solid white when I export my vertex animation texture using the sprite default and I can't work out where I'm going wrong, I was hoping someone could help me out. I've included a simple file that just spawns some particles in a popnet, then created the Cd and Alpha point attributes after in a wrangle. It all looks as expected when you view the VIZ_ALPHA null but when I view the _col.exe export its solid white. When I view the sprite example file from the GDC 2017 presentation (sprite_pig.hip) there is definitely alpha information in the color image (sprite_pig_col.exr), but when I export the same textures from the same file it's solid white again. Has something changed?

Also I was wondering if it's possible to split information up in the color image? For example use the red channel as an overlay in ue to randomize color, the green channel for width (pscale) etc or can UE read the pscale attribute?

Any help would be greatly appreciated, thanks in advance.

Adrian

Hi Adrian,

It's not just you. I can't seem to get the Alpha to export either. It works if I plug the result into one of the colour channels. I'm submitting a bug to the dev team.

As a quick fix you can unlock the Vertex Animation Texture node then go to /obj/alpha_test/texture_output/vertex_animation_textures1/sprite_copnet/calculate_Cd and under the Image tab set Add Plane to the first option - C, A(C:rgb A)

Hi Mike

Thanks for getting back to me so soon, I'll have a look at your fix tomorrow when I get back into work, and thanks also for submitting a bug, cheers.

Adrian

Was this fixed? im on the latest branch 1.29 and still experiencing the issue, also Mike/Adrian, are you guys noticing a “stepping” of the alpha when its played back in unreal? is this a precision issue?

I've made the change. You should see it in tomorrow's daily build. The stepping of the alpha could be your image type but unlikely or your compression setting in UE4. It's difficult to say without more info.

mikelyndon-sesi
I've made the change. You should see it in tomorrow's daily build. The stepping of the alpha could be your image type but unlikely or your compression setting in UE4. It's difficult to say without more info.

Ill double check tonight, I might have misassigned a texture

I seem to be unable to set an alpha value and export it. VAT is always outputting 0 for me. I'm setting @Alpha, that's the correct variable right?




and yet after a successful VAT export my texture's alpha is black: