132 lines
3.9 KiB
C++
132 lines
3.9 KiB
C++
#include <iostream>
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#include <vector>
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#include <algorithm>
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#include <cmath>
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#include <sstream>
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#include <fstream>
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#include <random>
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#include "vec.h"
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#define STB_IMAGE_WRITE_IMPLEMENTATION
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#include "stb_image_write.h"
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#define STB_IMAGE_IMPLEMENTATION
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#include "stb_image.h"
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int resolution = 128;
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int channel = 3;
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typedef struct samplePoints {
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std::vector<Vec3f> directions;
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std::vector<float> PDFs;
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}samplePoints;
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void setRGB(int x, int y, float alpha, unsigned char *data) {
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data[3 * (resolution * x + y) + 0] = uint8_t(alpha);
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data[3 * (resolution * x + y) + 1] = uint8_t(alpha);
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data[3 * (resolution * x + y) + 2] = uint8_t(alpha);
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}
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void setRGB(int x, int y, Vec3f alpha, unsigned char *data) {
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data[3 * (resolution * x + y) + 0] = uint8_t(alpha.x);
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data[3 * (resolution * x + y) + 1] = uint8_t(alpha.y);
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data[3 * (resolution * x + y) + 2] = uint8_t(alpha.z);
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}
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samplePoints squareToCosineHemisphere(int sample_count){
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samplePoints samlpeList;
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const int sample_side = static_cast<int>(floor(sqrt(sample_count)));
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std::random_device rd;
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std::mt19937 gen(rd());
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std::uniform_real_distribution<> rng(0.0, 1.0);
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for (int t = 0; t < sample_side; t++) {
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for (int p = 0; p < sample_side; p++) {
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double samplex = (t + rng(gen)) / sample_side;
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double sampley = (p + rng(gen)) / sample_side;
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double theta = 0.5f * acos(1 - 2*samplex);
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double phi = 2 * M_PI * sampley;
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Vec3f wi = Vec3f(sin(theta) * cos(phi), sin(theta) * sin(phi), cos(theta));
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float pdf = wi.z / PI;
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samlpeList.directions.push_back(wi);
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samlpeList.PDFs.push_back(pdf);
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}
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}
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return samlpeList;
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}
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Vec3f getEmu(int x, int y, int alpha, unsigned char *data, float NdotV, float roughness) {
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return Vec3f(data[3 * (resolution * x + y) + 0],
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data[3 * (resolution * x + y) + 1],
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data[3 * (resolution * x + y) + 2]);
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}
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Vec3f IntegrateEmu(Vec3f V, float roughness, float NdotV, Vec3f Ei) {
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Vec3f Eavg = Vec3f(0.0f);
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const int sample_count = 1024;
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Vec3f N = Vec3f(0.0, 0.0, 1.0);
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samplePoints sampleList = squareToCosineHemisphere(sample_count);
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for (int i = 0; i < sample_count; i++) {
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Vec3f L = sampleList.directions[i];
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Vec3f H = normalize(V + L);
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float NoL = std::max(L.z, 0.0f);
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float NoH = std::max(H.z, 0.0f);
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float VoH = std::max(dot(V, H), 0.0f);
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float NoV = std::max(dot(N, V), 0.0f);
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// TODO: To calculate Eavg here
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}
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return Eavg / sample_count;
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}
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int main() {
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unsigned char *Edata = stbi_load("./GGX_E_MC_LUT.png", &resolution, &resolution, &channel, 3);
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if (Edata == NULL)
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{
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std::cout << "ERROE_FILE_NOT_LOAD" << std::endl;
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return -1;
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}
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else
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{
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std::cout << resolution << " " << resolution << " " << channel << std::endl;
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// | -----> mu(j)
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// |
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// | rough（i）
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// flip it if you want to write the data on picture
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uint8_t data[resolution * resolution * 3];
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float step = 1.0 / resolution;
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Vec3f Eavg = Vec3f(0.0);
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for (int i = 0; i < resolution; i++)
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{
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float roughness = step * (static_cast<float>(i) + 0.5f);
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for (int j = 0; j < resolution; j++)
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{
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float NdotV = step * (static_cast<float>(j) + 0.5f);
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Vec3f V = Vec3f(std::sqrt(1.f - NdotV * NdotV), 0.f, NdotV);
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Vec3f Ei = getEmu((resolution - 1 - i), j, 0, Edata, NdotV, roughness);
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Eavg += IntegrateEmu(V, roughness, NdotV, Ei) * step;
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setRGB(i, j, 0.0, data);
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}
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for(int k = 0; k < resolution; k++)
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{
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setRGB(i, k, Eavg, data);
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}
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Eavg = Vec3f(0.0);
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}
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stbi_flip_vertically_on_write(true);
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stbi_write_png("GGX_Eavg_LUT.png", resolution, resolution, channel, data, 0);
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}
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stbi_image_free(Edata);
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return 0;
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} |