45 lines
1.4 KiB
GLSL
45 lines
1.4 KiB
GLSL
uniform sampler2D blendMap;
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uniform sampler2D colorMap;
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out vec4 FragColor;
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void main() {
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vec2 uv = gl_FragCoord.xy / screen;
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vec2 uv_left = uv + vec2(-1., 0.) / screen;
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vec2 uv_top = uv + vec2(0., 1.) / screen;
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vec2 uv_right = uv + vec2(1., 0.) / screen;
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vec2 uv_bottom = uv + vec2(0., -1.) / screen;
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// Fetch the blending weights for current pixel:
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vec4 topLeft = texture(blendMap, uv);
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float bottom = texture(blendMap, uv_bottom).g;
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float right = texture(blendMap, uv_right).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 = texture(colorMap, uv);
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vec4 Cleft = texture(colorMap, uv_left);
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vec4 Ctop = texture(colorMap, uv_top);
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vec4 Cright = texture(colorMap, uv_right);
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vec4 Cbottom = texture(colorMap, uv_bottom);
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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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FragColor = vec4(color / sum);
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}
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