81 lines
2.7 KiB
GLSL
81 lines
2.7 KiB
GLSL
#ifdef GL_ES
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precision mediump float;
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#endif
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uniform mat3 worldToOutput;
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uniform vec4 outputRect;
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varying vec4 inputRect[1];
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varying mat3 worldToInput[1];
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uniform vec2 center;
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uniform float radius;
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uniform float blur;
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float det(mat3 m) { return m[0][0] * m[1][1] - m[0][1] * m[1][0]; }
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float scale = sqrt(abs(det(worldToOutput)));
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vec2 center_ = (worldToOutput * vec3(center, 1.0)).xy;
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float rad_ = scale * max(radius, 0.0);
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const float pi = 3.141592653;
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const float pi_twice = 2.0 * pi;
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const float pi_half = pi / 2.0;
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void addPoint(inout vec4 rect, vec2 p) {
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rect.xy = min(rect.xy, p.xy);
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rect.zw = max(rect.zw, p.xy);
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}
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void addBlurredPointBox(inout vec4 rect, vec2 p)
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{
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// Remember the *definition* of angle: angle = arc length / radius
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// Build p's blurred angular range
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float distance = length(p - center_);
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float angle = atan(p.y - center_.y, p.x - center_.x);
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// If rad_ > 0, we assume that the blurred length is proportional to (distance - rad_);
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float dist_ = max(distance - rad_, 0.0);
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float blurLen = radians(max(blur, 0.0)) * dist_;
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// The actual blurring angle is then found as (blurLen_ / distance)
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float blur_ = blurLen / max(distance, 0.01); // Jump the singularity
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vec2 angleRange = vec2(angle - blur_, angle + blur_); // Couldn't make it an array with
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// explicit initialization... GLSL complained -.-
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// Include the points at angleRange's extremes
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addPoint(rect, center_ + distance * vec2(cos(angleRange.x), sin(angleRange.x)));
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addPoint(rect, center_ + distance * vec2(cos(angleRange.y), sin(angleRange.y)));
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// At pi/2 multiples we get a box extreme. Include them if present.
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float blur_twice = 2.0 * blur_;
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if(mod( - angleRange.x, pi_twice) < blur_twice)
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addPoint(rect, center_ + vec2(distance, 0.0));
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if(mod(pi_half - angleRange.x, pi_twice) < blur_twice)
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addPoint(rect, center_ + vec2(0.0, distance));
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if(mod(pi - angleRange.x, pi_twice) < blur_twice)
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addPoint(rect, center_ + vec2(-distance, 0.0));
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if(mod(-pi_half - angleRange.x, pi_twice) < blur_twice)
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addPoint(rect, center_ + vec2(0.0, -distance));
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}
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void main( void )
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{
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worldToInput[0] = worldToOutput; // Let the input and output references be the same
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inputRect[0] = outputRect;
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// Add the bounding box of each blurred corner
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addBlurredPointBox(inputRect[0], outputRect.xy);
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addBlurredPointBox(inputRect[0], outputRect.xw);
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addBlurredPointBox(inputRect[0], outputRect.zy);
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addBlurredPointBox(inputRect[0], outputRect.zw);
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gl_Position = vec4(0.0); // Does not link without
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}
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