Pass vertexColor buffer to shaderMaterial?

Questions
1

Hi :slight_smile:
I’m in need of rendering a unique color per triangle of a mesh, thinking of using a vertexColor buffer.
However, it must be separate from the mesh own vertexColors.

Is it possible to pass such a buffer to a shaderMaterial or custom shader?

I looked around, but was unable to find any information on it, few examples used “vColor” in shader code but turned out to just be a singlular color.

Any examples, documentation, pointers and/or other ideas to achieve it are more than welcome!
Thanks

3

I read that wrong sorry, I had to delete my response.

4

Here’s how to do it with a custom material:

https://playground.babylonjs.com/#MC11EY

With a ShaderMaterial, you need to pass the name of your custom attribute through the attributes property of the options parameter passed to the constructor.

1 Like
5

Interesting and so simple…
And it seems if the mesh has it’s own vertexColors these are simply ignored while the material used, awesome.
Thank you! :slight_smile:

6

awww, I should not have deleted my response then… I did read it right.

I thought you wanted each facet to have its own solid color, not blended between vertex colors… damn.||

If you are looking to do it with a customShader then in the constructor just add the “color” in the attributes section.

Then on the VertexFragment add the

attribute vec4 color;
varying vec4 vColor;

main(){
...
vColor = color;
...
}

it should then pass that attribute automatically for the shaderMaterial for you I belive.

was my original post, I added it back because it looks like popov covered doing it for the CustomMaterial only.

7

Be careful that you will collide with names (color and vcolor) already used by the engine when you enable vertex colors.

That’s why I used mycolor and vMyColor in my sample :wink:

1 Like
8

not on a customShader you wont, I dont think unless I am mistaken?

I might learn something here.

So even on a customShader we have those reserved by the engine and that creates conflicts?

9

default vertexColors buffer (BABYLON.VertexBuffer.ColorKind) is “color”, i think it will use those, no?

10

I would believe so, especially for a customShader. For the customMaterial I think Popov is 100% right. I might be mistaken though.

11

Yes, even for the ShaderMaterial material you have some reserved names, like position / normal / uv / color for the attributes, world / projection / … for the uniforms.

If your geometry has a “color” vertex buffer and the mesh is flagged to use vertex colors, you will get a “color” attribute in your shader.

1 Like
12

Don’t you have to declare “color” in the attribute list for the shader instance in the constructor though? Otherwise I was under the impression it did not.

13

Yes, you also have to say you want to use this attribute in the shader by passing its name through the constructor.

1 Like
14

Coming back to this looking to increase precision of the triangle display (no blending)
Can we set/use a custom UV buffer in a simular manner to @Evgeni_Popov solution ?

15

You can pass any buffer you want to the custom shader (in your GPU limit card).

For custom uv set, you would pass a vec2 buffer instead of a vec4 as in the sample.

1 Like
16

Thanks!
Sorry, complete shader-code noob :slight_smile:
managed to get it to work after a slight headache :smiley:

and now ofcourse,
i realise uv aproach won’t work when the mesh has shared positions…
not sure what i was thinking :thinking:

expected; https://playground.babylonjs.com/#MC11EY#5
actual: https://playground.babylonjs.com/#MC11EY#4