void main()

in src/engine/shaders/volumerender.frag [788:959]

• 152 lines of code
• 16 McCabe index (conditional complexity)

void main() {
  const float DELTA1 = 0.1;
  const float DELTA2 = 0.05;
  vec4 acc = vec4(0.0, 0.0, 0.0, 1.0);
  // To increase the points of the beginning and end of the ray and its direction
  vec2 tc = screenpos.xy / screenpos.w * 0.5 + 0.5;
//    gl_FragColor = vec4(0.0, 0.0, 1.0, 1.0);
//    return;
  vec4 backTexel = texture2D(texBF, tc, 0.0);
  vec3 back = backTexel.xyz;
  vec4 start = texture2D(texFF, tc, 0.0);

  if (length(back) < 0.001 || length(start.xyz) < 0.01) {
    gl_FragColor = vec4(0, 0, 0, 1.0);
	return;
  }
  vec3 dir = normalize(back - start.xyz);
  
  if (start.a < 0.3 || backTexel.a < 0.3) {
    gl_FragColor = vec4(0, 0, 0, 1.0);
	return;
  }
  
  if (length (back - start.xyz) < 0.03) {
    gl_FragColor = vec4(0.0, 0, 0, 1.0);
    return;
  }


  // Read texels adjacent to the pixel
  vec2 tc1 = tc.xy;
  vec2 tSize = isoSurfTexel;
  tc1 = tc1 - 0.5 * tSize;
  vec2 uv_fract = fract(tc1 / tSize);
  vec2 tex_dU = vec2(tSize.x, 0.0);
  vec2 tex_dV = vec2(0.0, tSize.y);
  vec4 iso1 = texture2D(texIsoSurface, tc1, 0.0);
  vec4 iso2 = texture2D(texIsoSurface, tc1 + tex_dU, 0.0);
  vec4 iso3 = texture2D(texIsoSurface, tc1 + tex_dV, 0.0);
  vec4 iso4 = texture2D(texIsoSurface, tc1 + tex_dU + tex_dV, 0.0);
  vec4 minIso = min(iso1, iso2);
  minIso = min(minIso, iso3);
  minIso = min(minIso, iso4);
  float delta = DELTA1;
  #if isoRenderFlag==1
  {
    delta = DELTA2;
  }
  #endif
  if (minIso.a > 1.9)
  {
    // The neighboring texels do not contain an isosurface
    gl_FragColor = vec4(0.0, 0, 0, 1.0);
    
    return;
  }
  if (length(iso1.rgb - iso2.rgb) < delta && length(iso1.rgb - iso3.rgb) < delta && length(iso1.rgb - iso4.rgb) < delta)
  {
    // The color of the pixel is calculated by bilinear interpolation of colors of neighboring texels
    acc = vec4(mix(mix(iso1.xyz, iso2.xyz, uv_fract.x), mix(iso3.xyz, iso4.xyz, uv_fract.x), uv_fract.y), 1.0);
    gl_FragColor = acc;
    return;
  }
  // Direct volume render
 #if isoRenderFlag==0
  {
     float vol = tex3D(start.xyz);
     if (vol > t_function2min.a)
        acc.rgb = 0.75*vol * t_function2min.rgb;
     else
        acc.rgb = VolumeRender(start.xyz  + max(0., minIso.a - 0. / 128.)*dir , dir, back).rgb;
     acc.a = 1.0;
     acc.rgb = (1.0 - contrast3D)*acc.rgb + contrast3D*vec3(vol);
     gl_FragColor = acc;
     return;
  }
  #endif
  // Direct isosurface render
  #if isoRenderFlag==1
  {
    //float v = length(start.xyz - back);
    //gl_FragColor = vec4(v, v, v, 1.0);
    //return;
    float vol = tex3D(start.xyz);
    if (vol > isoThreshold)
    {
      acc.rgb = vec3(vol);
   		acc.a = 1.0;
      gl_FragColor = acc;
      return;
    }
    else
    {
      acc = Isosurface(start.xyz + max(0., minIso.a - 1. / 128.)*dir, dir, back, isoThreshold);
//      acc = Isosurface(start.xyz, dir, back, isoThreshold);
      if (acc.a < 1.9)
      {
        acc.rgb = CalcLighting(acc.rgb, dir);
        //acc.rgb = (1.0 - contrast3D)*acc.rgb + contrast3D*vec3(vol);
      	acc.a = 1.0;
      }
      gl_FragColor = acc;
      return;
    }
  }
  #endif
 // Direct full volume render
 #if isoRenderFlag==3
  {
     acc.rgb = FullVolumeRender(start.xyz + max(0., minIso.a - 0. / 128.)*dir, dir, back).rgb;
     acc.a = 1.0;
     gl_FragColor = acc;
     return;
  }
  #endif
  
  // Direct volume render with ROI
  #if isoRenderFlag==4
  {
     vec4 vol = tex3DRoi(start.xyz);
     if (vol.a > 0.75)
        acc.rgb = 0.75 * vol.rgb;
     else
      //  acc.rgb = RoiVolumeRender(start.xyz, dir, back).rgb;
       acc.rgb = RoiVolumeRender(start.xyz + max(0., minIso.a - 0. / 128.)*dir, dir, back).rgb;
     acc.a = 1.0;
     gl_FragColor = acc;
     return;
  }
  #endif

  //Direct isosurface render with ROI
  #if isoRenderFlag == 5
  {
    //float v = tex3DRoi(start.xyz).a;
    //gl_FragColor = vec4(v, v, v, 1.0);
    //return;
    float Threshold = 0.3 * isoThreshold + 0.5;
    acc = IsosurfaceRoi(start.xyz + max(0., minIso.a - 1. / 128.)*dir, dir, back, Threshold, stepSize.b);
    if (acc.a < 1.9)
    {
        vec4 vol = tex3DRoi(start.xyz);
        if (vol.a > Threshold)//t_function2min.a)
            acc.rgb = 0.75 * vol.rgb;
        else
        {
          const float AMBIENT = 0.3;
          const float DIFFUSE = 0.7;
          const float SPEC = 0.1;
          const float SPEC_POV = 90.0;
          vec3 N = CalcNormalRoi(acc.rgb);
          float dif = max(0.0, dot(N, -lightDir));
          float specular = pow(max(0.0, dot(normalize(reflect(lightDir, N)), dir)), SPEC_POV);
//          acc.rgb = (0.5*(brightness3D + 1.5)*(DIFFUSE * dif + AMBIENT * computeSsaoShadow(acc.rgb, N, Threshold) ) + SPEC * specular) * tex3DRoi(acc.rgb).rgb;
          acc.rgb = (0.5*(brightness3D + 1.5)*(DIFFUSE * dif + AMBIENT) + SPEC * specular) * tex3DRoi(acc.rgb).rgb;
//          acc.rgb = computeSsaoShadow(acc.rgb, Threshold) * vec3(1.0, 1.0, 1.0);
        }  
		acc.a = 1.0;
    }
    gl_FragColor = acc;
    return;
  }
  #endif
  // Render of maximum intensity
  #if isoRenderFlag == 2
  {
    acc.rgb = MipRender(start.xyz, dir, back).rgb;
    gl_FragColor = acc;
    return;
  }
  #endif
}