27 lines
746 B
GLSL
27 lines
746 B
GLSL
// pathfinder/shaders/gles2/ecaa-line.vs.glsl
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//
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// Copyright (c) 2017 Mozilla Foundation
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precision highp float;
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uniform bool uLowerPart;
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varying vec4 vEndpoints;
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void main() {
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// Unpack.
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vec2 center = gl_FragCoord.xy;
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vec2 p0 = vEndpoints.xy, p1 = vEndpoints.zw;
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// Set up Liang-Barsky clipping.
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vec4 pixelExtents = center.xxyy + vec4(-0.5, 0.5, -0.5, 0.5);
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vec4 p = (p1 - p0).xxyy, q = pixelExtents - p0.xxyy;
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// Use Liang-Barsky to clip to the left and right sides of this pixel.
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vec2 t = clamp(q.xy / p.xy, 0.0, 1.0);
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vec2 spanP0 = p0 + p.yw * t.x, spanP1 = p0 + p.yw * t.y;
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// Compute area.
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gl_FragColor = vec4(computeCoverage(p0, p1, spanP0, spanP1, t, pixelExtents, p, q, uLowerPart));
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}
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