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/*=========================================================================
Program: Visualization Toolkit
Module: vtkGPUVolumeRayCastMapper_ScaleBiasFS.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.
=========================================================================*/
// This fragment shader scales and biases a framebuffer passed as a texture.
// Incoming color from the texture is pre-multiplied by alpha.
// It does not affect the alpha component.
// Passing the framebuffer as a texture allows the use of a reduction factor
// compared to the size of the final image.
#version 110
// Framebuffer to scale.
uniform sampler2D frameBufferTexture;
uniform float scale;
uniform float bias;
void main()
{
vec4 color=texture2D(frameBufferTexture,gl_TexCoord[0].xy);
if(color.a==0.0)
{
discard;
}
// As incoming color is pre-multiplied by alpha, the bias has to be
// multiplied by alpha before adding it.
gl_FragColor.r=color.r*scale+bias*color.a;
gl_FragColor.g=color.g*scale+bias*color.a;
gl_FragColor.b=color.b*scale+bias*color.a;
gl_FragColor.a=color.a;
}
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