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66 lines
2.3 KiB
GLSL
66 lines
2.3 KiB
GLSL
#version 110
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// www.OpenTK.net GLSL Julia Set (c) 2008 Christoph Brandtner
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// uniforms from OpenGL
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uniform sampler1D COLORTABLE;
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uniform float CETX;
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uniform float CETY;
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uniform float SCALINGX;
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uniform float SCALINGY;
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uniform float OFFSETX;
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uniform float OFFSETY;
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// GLSL internal variables.
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const int MAXIterations = 16; // must be greater than zero, 16 is a good blend between detail and speed
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float XPos;
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float YPos;
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float XQuad;
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float YQuad; // half precision floating point could be used on those 4 floats for speed, but will throw a warning.
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int TableIndex;
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int LoopCount;
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// this function reduces duplicate code
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void Iterate(void)
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{
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YPos = 2.0 * XPos * YPos + CETY;
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XPos = XQuad - YQuad + CETX;
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XQuad = pow(XPos, 2.0);
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YQuad = pow(YPos, 2.0);
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TableIndex++;
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if ( (XQuad + YQuad) > 4.0 ) LoopCount = MAXIterations; // skip further iterations for this Pixel
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LoopCount++;
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}
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// Shader entry point, this is executed per Pixel
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void main(void)
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{
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XPos = gl_FragCoord.x / SCALINGX - OFFSETX;
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YPos = gl_FragCoord.y / SCALINGY - OFFSETY;
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XQuad = pow(XPos, 2.0);
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YQuad = pow(YPos, 2.0);
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TableIndex = -1;
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LoopCount = 0;
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// the loop is unrolled for SM 2.0 compatibility
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if ( LoopCount <= MAXIterations ) Iterate(); // TableIndex==0
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if ( LoopCount > 1 ) discard; // attempt to early-out, will affect ~1/3 of all Pixels
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate();
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if ( LoopCount <= MAXIterations ) Iterate(); // TableIndex==16
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float FinalTableIndex = float( TableIndex ) / float( MAXIterations );
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gl_FragColor = texture1D( COLORTABLE, FinalTableIndex ); // lookup texture for output
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// gl_FragColor.rgb = vec3(FinalTableIndex); // Debug: output greyscale
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} |