OpenSpace/modules/space/shaders/psfToTexture_fs.glsl

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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2023                                                               *
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#version __CONTEXT__

in vec2 psfCoords;

out vec4 renderTableColor;

uniform int psfMethod;
uniform float p0Param;
uniform float p1Param;
uniform float p2Param;
uniform float alphaConst;
uniform float FWHM;
uniform float betaConstant;

const int PsfMethodSpencer = 0;
const int PsfMethodMoffat = 1;


void main() {
  vec4 fullColor = vec4(0.0, 0.0, 0.0, 1.0);
  if (psfMethod == PsfMethodSpencer) {
    // PSF Functions from paper: Physically-Based Galre Effects for Digital
    // Images - Spencer, Shirley, Zimmerman and Greenberg.
    float theta = sqrt((psfCoords.y * psfCoords.y + psfCoords.x * psfCoords.x)) * 90.0;
    float f0 = 2.61E6 * exp(-pow(theta / alphaConst, 2.0));
    float f1 = 20.91 / pow(theta + alphaConst, 3.0);
    float f2 = 72.37 / pow(theta + alphaConst, 2.0);
    float spencer = p0Param * f0 + p1Param * f1 + p2Param * f2;
    fullColor = vec4(spencer);
  }
  else if (psfMethod == PsfMethodMoffat) {
    // Moffat
    float r = sqrt((psfCoords.y * psfCoords.y + psfCoords.x * psfCoords.x)) * 90.0;
    float alpha = FWHM / (2.0 * sqrt(pow(2.0, 1.0 / betaConstant) - 1.0));
    float moffat = pow(1.0 + (r/alpha) * (r/alpha), -betaConstant);
    fullColor = vec4(moffat);
  }

  if (fullColor.a == 0) {
    discard;
  }

  renderTableColor = fullColor;
}