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uint8_t BitReverse(uint8_t x)
{
    x = ((x & 0x0F) <<  4) | ((x & 0xF0) >>  4);
    x = ((x & 0x33) <<  2) | ((x & 0xCC) >>  2);
    x = ((x & 0x55) <<  1) | ((x & 0xAA) >>  1);
    
    return x;
}

uint16_t BitReverse(uint16_t x)

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// Helper function: sample the visible hemisphere from a spherical cap
vec3 SampleVndf_Hemisphere(vec2 u, vec3 wi)
{
	// sample a spherical cap in (-wi.z, 1]
	float phi = 2.0f * M_PI * u.x;
	float z = fma((1.0f - u.y), (1.0f + wi.z), -wi.z);
	float sinTheta = sqrt(clamp(1.0f - z * z, 0.0f, 1.0f));
	float x = sinTheta * cos(phi);
	float y = sinTheta * sin(phi);
	vec3 c = vec3(x, y, z);

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// sorts an array in ascending order (arraySize muste be a power of two)
void BitonicSort(uint32_t *array, uint32_t arraySize)
{
    for (uint32_t d2 = 1u; d2 < arraySize; d2*= 2u) {
        for (uint32_t d1 = d2; d1 >= 1u; d1/= 2u) {
            const uint32_t mask = (0xFFFFFFFEu * d1);

#pragma omp parallel for
            for (uint32_t i = 0; i < (arraySize / 2); ++i) {
                const uint32_t i1 = ((i << 1) & mask) | (i & ~(mask >> 1));

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#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>

// inverting piecewise linear functions
float InverseLinear(float yStart, float yEnd, float y)
{
    return (y - yStart) / (yEnd - yStart);
}