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48 lines
1.5 KiB
GLSL
48 lines
1.5 KiB
GLSL
// ============================================================================
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//
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// Program: Visualization Toolkit
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// Module: vtkSobelGradientMagnitudePassShader1_fs.glsl
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//
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// Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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// All rights reserved.
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// See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//
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// ============================================================================
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// Fragment shader used by the first pass of the Sobel filter render pass.
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#version 110
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// GLSL Spec 1.10 rev 59 30-April-2004 defines gl_FragData[] but implementation
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// older than the spec only has it as an extension
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// (nVidia Linux driver 100.14.13, OpenGL version 2.1.1,
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// on Quadro FX 3500/PCI/SSE2)
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#extension GL_ARB_draw_buffers : enable
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uniform sampler2D source;
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uniform float stepSize; // 1/W
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void main(void)
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{
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vec2 tcoord=gl_TexCoord[0].st;
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vec2 offset=vec2(stepSize,0.0);
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vec4 t1=texture2D(source,tcoord-offset);
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vec4 t2=texture2D(source,tcoord);
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vec4 t3=texture2D(source,tcoord+offset);
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// Gx
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// version with unclamped float textures t3-t1 will be in [-1,1]
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// gl_FragData[0]=t3-t1;
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// version with clamped unchar textures (t3-t1+1)/2 stays in [0,1]
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gl_FragData[0]=(t3-t1+1.0)/2.0;
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// Gy
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gl_FragData[1]=(t1+2.0*t2+t3)/4.0;
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}
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