39 lines
1.3 KiB
GLSL
39 lines
1.3 KiB
GLSL
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varying vec4 offset[2];
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uniform sampler2D blendMap;
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uniform sampler2D colorMap;
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void main() {
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// Fetch the blending weights for current pixel:
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vec4 topLeft = texture2D(blendMap, gl_TexCoord[0].xy);
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float bottom = texture2D(blendMap, offset[1].zw).g;
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float right = texture2D(blendMap, offset[1].xy).a;
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vec4 a = vec4(topLeft.r, bottom, topLeft.b, right);
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// Up to 4 lines can be crossing a pixel (one in each edge). So, we perform
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// a weighted average, where the weight of each line is 'a' cubed, which
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// favors blending and works well in practice.
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vec4 w = a * a * a;
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// There is some blending weight with a value greater than 0.0?
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float sum = dot(w, vec4(1.0));
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if (sum < 1e-5)
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discard;
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vec4 color = vec4(0.0);
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// Add the contributions of the possible 4 lines that can cross this pixel:
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vec4 C = texture2D(colorMap, gl_TexCoord[0].xy);
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vec4 Cleft = texture2D(colorMap, offset[0].xy);
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vec4 Ctop = texture2D(colorMap, offset[0].zw);
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vec4 Cright = texture2D(colorMap, offset[1].xy);
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vec4 Cbottom = texture2D(colorMap, offset[1].zw);
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color = mix(C, Ctop, a.r) * w.r + color;
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color = mix(C, Cbottom, a.g) * w.g + color;
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color = mix(C, Cleft, a.b) * w.b + color;
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color = mix(C, Cright, a.a) * w.a + color;
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// Normalize the resulting color and we are finished!
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gl_FragColor = color / sum;
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}
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