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//VTK::System::Dec
// ============================================================================
//
// Program: Visualization Toolkit
// Module: vtkSSAAPassFS.glsl
//
// Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// All rights reserved.
// See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
//
// This software is distributed WITHOUT ANY WARRANTY; without even
// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE. See the above copyright notice for more information.
//
// ============================================================================
// thanks to Brad Larson for posting sample code that helped get this started
uniform sampler2D source;
// the output of this shader
//VTK::Output::Dec
uniform float texelWidthOffset;
uniform float texelHeightOffset;
varying vec2 tcoordVC;
// Note that the texel offsets should be 3/8 of a pixel in the
// resulting image not the source image. Also note that this
// filter is meant to be run one dimension at a time.
// in the equation below 1.5 corresponds to 4 texel offsets
// aka 3/8 * 4 = 1.5
// sinc(x) * sinc(x/a) = (a * sin(pi * x) * sin(pi * x / a)) / (pi^2 * x^2)
// Assuming a Lanczos constant of 2.0, and scaling values to max out at x = +/- 1.5
void main()
{
vec2 firstOffset = vec2(texelWidthOffset, texelHeightOffset);
vec4 fragmentColor = texture2D(source, tcoordVC) * 0.38026;
fragmentColor += texture2D(source, tcoordVC - firstOffset) * 0.27667;
fragmentColor += texture2D(source, tcoordVC + firstOffset) * 0.27667;
fragmentColor += texture2D(source, tcoordVC - 2.0*firstOffset) * 0.08074;
fragmentColor += texture2D(source, tcoordVC + 2.0*firstOffset) * 0.08074;
fragmentColor += texture2D(source, tcoordVC - 3.0*firstOffset) * -0.02612;
fragmentColor += texture2D(source, tcoordVC + 3.0*firstOffset) * -0.02612;
fragmentColor += texture2D(source, tcoordVC - 4.0*firstOffset) * -0.02143;
fragmentColor += texture2D(source, tcoordVC + 4.0*firstOffset) * -0.02143;
gl_FragData[0] = fragmentColor;
}
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