     	// front-to-back integration
     	if (colorSample.a > 0.0) {
     	    // accomodate for variable sampling rates (base interval defined by mod_compositing.frag)
-    	    colorSample.a = 1.0 - pow(1.0 - colorSample.a, StepSize*200.0f);
+    	    colorSample.a = 1.0 - pow(1.0 - colorSample.a, StepSize * 200.0f);
     	    colorAcum.rgb += (1.0 - colorAcum.a) * colorSample.rgb * colorSample.a;
     	    colorAcum.a += (1.0 - colorAcum.a) * colorSample.a;
     	}

uniform sampler1D TransferFunc;  
uniform float     StepSize;
uniform vec2      ScreenSize;
uniform vec4      backgroundColor = vec4(1, 1, 1, 0);
layout (location = 0) out vec4 FragColor;

void main()
{
    // ExitPointCoord is normalized device coordinate
    vec3 exitPoint = texture(ExitPoints, gl_FragCoord.st/ScreenSize).xyz;
    // that will actually give you clip-space coordinates rather than
    // normalised device coordinates, since you're not performing the perspective
    // division which happens during the rasterisation process (between the vertex

    float lengthAcum = 0.0;
    vec4 colorSample; // The src color 
    float alphaSample; // The src alpha
 
    for(int i = 0; i < 1600; i++)
    {
