69 lines
1.9 KiB
GLSL
69 lines
1.9 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 sampler2D inputImage[1];
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uniform mat3 outputToInput[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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mat3 worldToInput = outputToInput[0] * worldToOutput;
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vec2 center_s = (worldToOutput * vec3(center, 1.0)).xy;
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float scale_s = sqrt(abs(det(worldToOutput)));
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float rad_s = scale_s * max(radius, 0.0);
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#define STEPS_PER_PIXEL 4.0
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void main( void )
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{
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// Build lengths on output metrics
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vec2 v = gl_FragCoord.xy - center_s;
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float distance_s = length(v);
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float angle = atan(v.y, v.x);
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float dist_s = max(distance_s - rad_s, 0.0);
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float blurLen_s = radians(max(blur, 0.0)) * dist_s;
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float blur_ = blurLen_s / max(distance_s, 0.01); // Jump the singularity
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// Putting a maximum samples count - to prevent freezes; besides, blurring too many
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// pixels is typically useless...
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int samplesCount = int(clamp(ceil(blurLen_s * STEPS_PER_PIXEL), 1.0, 2000.0));
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float angle_step = blur_ / float(samplesCount);
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float cos_step = cos(angle_step);
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float sin_step = sin(angle_step);
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mat2 rot_step0 = mat2(cos_step, sin_step, -sin_step, cos_step);
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mat2 rot_step1 = mat2(cos_step, -sin_step, sin_step, cos_step);
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// Perform filtering
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vec4 pix = texture2D(inputImage[0], (outputToInput[0] * vec3(gl_FragCoord.xy, 1.0)).xy);
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vec2 v0 = rot_step0 * v, v1 = rot_step1 * v;
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for(int s = 1; s < samplesCount; ++s)
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{
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pix += texture2D(inputImage[0], (outputToInput[0] * vec3(center_s + v0, 1.0)).xy);
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pix += texture2D(inputImage[0], (outputToInput[0] * vec3(center_s + v1, 1.0)).xy);
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v0 = rot_step0 * v0, v1 = rot_step1 * v1;
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}
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gl_FragColor = pix / float(2 * samplesCount - 1);
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}
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