source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_pixel_frag.glsl


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uniform mat4 ProjectionMatrix;
uniform mat4 ViewMatrix;

uniform sampler2D strokeColor;
uniform sampler2D strokeDepth;

uniform int size[3];
uniform vec4 color;

uniform vec3 loc;
uniform float pixsize; /* rv3d->pixsize */
uniform float pixfactor;

out vec4 FragColor;

int uselines = size[2];
float defaultpixsize = pixsize * (1000.0 / pixfactor);
vec2 nsize = max(vec2(size[0], size[1]), 3.0);

/* This pixelation shader is a modified version of original Geeks3d.com code */
void main()
{
  vec2 uv = vec2(gl_FragCoord.xy);
  vec4 nloc = ProjectionMatrix * ViewMatrix * vec4(loc.xyz, 1.0);

  float dx = (ProjectionMatrix[3][3] == 0.0) ? (nsize[0] / (nloc.z * defaultpixsize)) :
                                               (nsize[0] / defaultpixsize);
  float dy = (ProjectionMatrix[3][3] == 0.0) ? (nsize[1] / (nloc.z * defaultpixsize)) :
                                               (nsize[1] / defaultpixsize);

  dx = max(abs(dx), 3.0);
  dy = max(abs(dy), 3.0);

  vec2 coord = vec2(dx * floor(uv.x / dx), dy * floor(uv.y / dy));

  float stroke_depth = texelFetch(strokeDepth, ivec2(coord), 0).r;
  vec4 outcolor = texelFetch(strokeColor, ivec2(coord), 0);

  if (uselines == 1) {
    float difx = uv.x - (floor(uv.x / nsize[0]) * nsize[0]);
    if ((difx == 0.5) && (outcolor.a > 0)) {
      outcolor = color;
    }
    float dify = uv.y - (floor(uv.y / nsize[1]) * nsize[1]);
    if ((dify == 0.5) && (outcolor.a > 0)) {
      outcolor = color;
    }
  }
  gl_FragDepth = stroke_depth;
  FragColor = outcolor;
}