FPGA friendly local random seed generator

Author: Luc Forget

include/constant_medium.hpp

@@ -60,7 +60,7 @@ class constant_medium {
     /// Distance between the two hitpoints affect of probability
     /// of the ray hitting a smoke particle
     const auto distance_inside_boundary = (rec2.t - rec1.t) * ray_length;
-    auto rng = LocalPseudoRNG { toseed(r.direction()) ^ toseed(r.origin()) };
+    auto rng = LocalPseudoRNG { toseed(r.direction(), r.origin()) };
     const auto hit_distance = neg_inv_density * sycl::log(rng.real());
 
     /// With lower density, hit_distance has higher probabilty

include/material.hpp

@@ -17,7 +17,7 @@ struct lambertian_material {
 
   bool scatter(const ray& r_in, const hit_record& rec, color& attenuation,
                ray& scattered) const {
-    LocalPseudoRNG rng {  toseed(r_in.direction()) ^ toseed(r_in.origin()) };
+    LocalPseudoRNG rng {  toseed(r_in.direction(), r_in.origin()) };
     vec scatter_direction = rec.normal + rng.unit_vec();
     scattered = ray(rec.p, scatter_direction, r_in.time());
     // Attenuation of the ray hitting the object is modified based on the color
@@ -37,7 +37,7 @@ struct metal_material {
 
   bool scatter(const ray& r_in, const hit_record& rec, color& attenuation,
                ray& scattered) const {
-    LocalPseudoRNG rng {  toseed(r_in.direction()) ^ toseed(r_in.origin()) };
+    LocalPseudoRNG rng {  toseed(r_in.direction(), r_in.origin()) };
     vec reflected = reflect(unit_vector(r_in.direction()), rec.normal);
     scattered = ray(rec.p, reflected + fuzz * rng.in_unit_ball(), r_in.time());
     // Attenuation of the ray hitting the object is modified based on the color
@@ -68,7 +68,7 @@ struct dielectric_material {
                ray& scattered) const {
     // Attenuation of the ray hitting the object is modified based on the color
     // at hit point
-    LocalPseudoRNG rng {  toseed(r_in.direction()) ^ toseed(r_in.origin()) };
+    LocalPseudoRNG rng {  toseed(r_in.direction(), r_in.origin()) };
     attenuation *= albedo;
     real_t refraction_ratio = rec.front_face ? (1.0f / ref_idx) : ref_idx;
     vec unit_direction = unit_vector(r_in.direction());
@@ -116,7 +116,7 @@ struct isotropic_material {
 
   bool scatter(const ray& r_in, const hit_record& rec, color& attenuation,
                ray& scattered) const {
-    LocalPseudoRNG rng {  toseed(r_in.direction()) ^ toseed(r_in.origin()) };
+    LocalPseudoRNG rng {  toseed(r_in.direction(), r_in.origin()) };
     scattered = ray(rec.p, rng.in_unit_ball(), r_in.time());
     attenuation *= dev_visit([&](auto&& t) { return t.value(rec); }, albedo);
     return true;

include/rtweekend.hpp

@@ -3,6 +3,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
 #include <cstdlib>
 #include <cstring>
 #include <limits>
@@ -45,6 +46,23 @@ uint32_t toseed(vec const& val) {
   return x * x * y * y * z * z;
 }
 
+uint32_t toseed(vec const& val1, vec const& val2) {
+  uint32_t x1, y1, z1, x2, y2, z2;
+  std::memcpy(&x1, &val1.x(), sizeof(uint32_t));
+  std::memcpy(&y1, &val1.y(), sizeof(uint32_t));
+  std::memcpy(&z1, &val1.z(), sizeof(uint32_t));
+  std::memcpy(&x2, &val2.x(), sizeof(uint32_t));
+  std::memcpy(&y2, &val2.y(), sizeof(uint32_t));
+  std::memcpy(&z2, &val2.z(), sizeof(uint32_t));
+  uint32_t shifted1 = x1 << 26;
+  uint32_t shifted2 = (x2 & 63) << 21;
+  uint32_t shifted3 = (y1 & 63) << 15;
+  uint32_t shifted4 = (y2 & 63) << 10;
+  uint32_t shifted5 = (z1 & 63) << 5;
+  uint32_t shifted6 = (z2 & 63);
+  return shifted1 ^ shifted2 ^ shifted3 ^ shifted4 ^ shifted5 ^ shifted6;
+}
+
 class LocalPseudoRNG {
  public:
   inline LocalPseudoRNG(std::uint32_t init_state = xorshift<>::initial_state)

src/main.cpp

@@ -2,6 +2,7 @@
 #include <algorithm>
 #include <chrono>
 #include <cstdint>
+#include <ctime>
 #include <iostream>
 #include <iterator>
 #include <math.h>
@@ -79,17 +80,29 @@ int main(int argc, char* argv[]) {
   hittables.emplace_back(sphere(point { 0, -1000, 0 }, 1000, m));
   t = checker_texture(color { 0.9f, 0.9f, 0.9f }, color { 0.4f, 0.2f, 0.1f });
 
-  LocalPseudoRNG rng;
+  LocalPseudoRNG rng{static_cast<uint32_t>(std::time(nullptr))};
 
-  for (int a = -11; a < 11; a += 3) {
-    for (int b = -11; b < 11; b += 3) {
+  for (int a = -11; a < 11; a++) {
+    for (int b = -11; b < 11; b++) {
+      auto choose_mat = rng.real();
       // Spheres are placed at a point randomly displaced from a,b
       point center(a + 0.9f * rng.real(), 0.2f, b + 0.9f * rng.real());
-      if (sycl::length((center - point(4, 0.2f, 0))) > 0.9f) {
+      if (choose_mat < 0.70f) {
         // Lambertian
         auto albedo = rng.vec_t() * rng.vec_t();
         hittables.emplace_back(
             sphere(center, 0.2f, lambertian_material(albedo)));
+      } else if (choose_mat < 0.95f) {
+        // metal
+        auto albedo = rng.vec_t(0.5f, 1);
+        auto fuzz = rng.real(0, 0.5f);
+        hittables.emplace_back(
+            sphere(center, 0.2f, metal_material(albedo, fuzz)));
+      } else {
+        // glass
+        hittables.emplace_back(
+            sphere(center, 0.2f,
+                   dielectric_material(1.5f, color { 1.0f, 1.0f, 1.0f })));
       }
     }
   }
@@ -127,23 +140,20 @@ int main(int argc, char* argv[]) {
   hittables.emplace_back(sphere(point { 0, 1, -2.25f }, 1,
                                 metal_material(color(0.7f, 0.6f, 0.5f), 0.0f)));
 
-  // t = image_texture::image_texture_factory("../images/SYCL.png", 5);
-
-  // // Add a sphere with a SYCL logo in the background
   hittables.emplace_back(
       sphere { point { -60, 3, 5 }, 4, lambertian_material { t } });
 
   // Add a metallic monolith
   hittables.emplace_back(
       box { point { 6.5f, 0, -1.5f }, point { 7.0f, 3.0f, -1.0f },
-            metal_material { color { 0.7f, 0.6f, 0.5f }, 0.25f } });/**/
+            metal_material { color { 0.7f, 0.6f, 0.5f }, 0.25f } });
 
   // Add a smoke ball
   sphere smoke_sphere =
       sphere { point { 5, 1, 3.5f }, 1,
                lambertian_material { color { 0.75f, 0.75f, 0.75f } } };
-  /*hittables.emplace_back(
-      constant_medium { smoke_sphere, 1, color { 1, 1, 1 } });*/
+  hittables.emplace_back(
+      constant_medium { smoke_sphere, 1, color { 1, 1, 1 } });
 
   // SYCL queue
   sycl::queue myQueue;