Shader compiler error with GrayScalePostProcessor example from docs

[mattjennings]

It seems the shader fails to compile the example grayscale shader from the docs

Replication: https://codesandbox.io/s/excalibur-shader-i0q8u2?file=/src/index.js

Error:

Could not link the program: [Fragment shader version does not match other shader versions.]

I know very little about shaders, but the built-in color blindness post processor does work, so perhaps I'm doing something wrong here with this custom one

[mattjennings]

I managed to get it working by comparing to the color blind fragment shader and updating some of the syntax.

So I guess the example just needs to be updated! (I have no idea if this is the right way to do it - but it works!)

#version 300 es
precision mediump float;

// our texture
uniform sampler2D u_image;

// the texCoords passed in from the vertex shader.
in vec2 v_texcoord;

out vec4 fragColor;

void main() {
  vec4 tex = texture(u_image, v_texcoord);
  float avg = 0.2126 * tex.r + 0.7152 * tex.g + 0.0722 * tex.b;
  fragColor = vec4(avg, avg, avg, 1.0);
}

[eonarheim]

Hi @mattjennings I think this is 100% correct!

I'll update the docs with that snippet 👍

[eonarheim]

excaliburjs/excaliburjs.github.io@ec0b907