55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
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float log10(float x) {
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return log(x) / log(10.0);
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}
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float satf(float x) {
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return clamp(x, 0.0, 1.0);
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}
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vec2 satv(vec2 x) {
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return clamp(x, vec2(0.0), vec2(1.0));
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}
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float max2(vec2 v) {
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return max(v.x, v.y);
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}
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vec4 gridColor(vec2 uv, vec2 camPos) {
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vec2 dudv = vec2(
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length(vec2(dFdx(uv.x), dFdy(uv.x))),
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length(vec2(dFdx(uv.y), dFdy(uv.y)))
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);
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float lodLevel = max(0.0, log10((length(dudv) * gridMinPixelsBetweenCells) / gridCellSize) + 1.0);
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float lodFade = fract(lodLevel);
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// cell sizes for lod0, lod1 and lod2
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float lod0 = gridCellSize * pow(10.0, floor(lodLevel));
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float lod1 = lod0 * 10.0;
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float lod2 = lod1 * 10.0;
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// each anti-aliased line covers up to 4 pixels
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dudv *= 4.0;
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// set grid coordinates to the centers of anti-aliased lines for subsequent alpha calculations
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uv += dudv * 0.5;
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// calculate absolute distances to cell line centers for each lod and pick max X/Y to get coverage alpha value
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float lod0a = max2( vec2(1.0) - abs(satv(mod(uv, lod0) / dudv) * 2.0 - vec2(1.0)) );
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float lod1a = max2( vec2(1.0) - abs(satv(mod(uv, lod1) / dudv) * 2.0 - vec2(1.0)) );
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float lod2a = max2( vec2(1.0) - abs(satv(mod(uv, lod2) / dudv) * 2.0 - vec2(1.0)) );
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uv -= camPos;
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// blend between falloff colors to handle LOD transition
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vec4 c = lod2a > 0.0 ? gridColorThick : lod1a > 0.0 ? mix(gridColorThick, gridColorThin, lodFade) : gridColorThin;
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// calculate opacity falloff based on distance to grid extents
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float opacityFalloff = (1.0 - satf(length(uv) / gridSize));
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// blend between LOD level alphas and scale with opacity falloff
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c.a *= (lod2a > 0.0 ? lod2a : lod1a > 0.0 ? lod1a : (lod0a * (1.0-lodFade))) * opacityFalloff;
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return c;
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}
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