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55 lines
1.5 KiB
GLSL
55 lines
1.5 KiB
GLSL
// ============================================================================
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//
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// Program: Visualization Toolkit
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// Module: vtkSobelGradientMagnitudePassShader2_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 second pass of the Sobel filter render pass.
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#version 110
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uniform sampler2D gx1;
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uniform sampler2D gy1;
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uniform float stepSize; // 1/H
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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(0.0,stepSize);
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// Gx
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vec4 tx1=texture2D(gx1,tcoord-offset);
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vec4 tx2=texture2D(gx1,tcoord);
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vec4 tx3=texture2D(gx1,tcoord+offset);
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// if clamped textures, rescale values from [0,1] to [-1,1]
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tx1=tx1*2.0-1.0;
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tx2=tx2*2.0-1.0;
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tx3=tx3*2.0-1.0;
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vec4 gx=(tx1+2.0*tx2+tx3)/4.0;
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// Gy
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vec4 ty1=texture2D(gy1,tcoord-offset);
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vec4 ty3=texture2D(gy1,tcoord+offset);
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vec4 gy=ty3-ty1;
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// the maximum gradient magnitude is sqrt(2.0) when for example gx=1 and
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// gy=1
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// gl_FragColor=sqrt((gx*gx+gy*gy)/2.0);
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gl_FragColor.rgb=sqrt((gx.rgb*gx.rgb+gy.rgb*gy.rgb)/2.0);
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gl_FragColor.a=1.0; // arbitrary choice.
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}
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