Fix casting (after integer overflow) in hash(...) function.

Makefile

@@ -52,10 +52,12 @@ examples: release
 	./target/release/examples/geometry_spherical_direction_vec3
 	./target/release/examples/geometry_vector2_null
 	./target/release/examples/geometry_vector3_null
+	./target/release/examples/integrators_sspm_hash.rs
 	./target/release/examples/lights_diffuse_area_light_new
 	./target/release/examples/lights_distant_light_new
 	./target/release/examples/lights_infinite_area_light_new
 	./target/release/examples/lights_point_light_new
+	./target/release/examples/parse_ass_file.rs
 	./target/release/examples/pbrt_spheres_differentials_texfilt
 	./target/release/examples/pbrt_teapot_area_light
 	./target/release/examples/pest_test

examples/integrators_sspm_hash.rs

@@ -0,0 +1,19 @@
+extern crate pbrt;
+
+use pbrt::core::geometry::Point3i;
+
+fn hash(p: &Point3i, hash_size: i32) -> usize {
+    (((p.x * 73856093) ^ (p.y * 19349663) ^ (p.z * 83492791)) as u32 % hash_size as u32) as usize
+}
+
+fn main() {
+    let photon_grid_index: Point3i = Point3i {
+        x: 225,
+        y: 0,
+        z: 267,
+    };
+    let hash_size: usize = 700000;
+    let h: usize = hash(&photon_grid_index, hash_size as i32);
+    assert!(h < hash_size, "hash({:?}, {:?})", photon_grid_index, hash_size);
+    println!("hash({:?}, {:?}) = {}", photon_grid_index, hash_size, h);
+}

src/integrators/sppm.rs

@@ -108,8 +108,8 @@ fn to_grid(p: &Point3f, bounds: &Bounds3f, grid_res: &[i32; 3], pi: &mut Point3i
     in_bounds
 }
 
-fn hash(p: &Point3i, hash_size: usize) -> usize {
-    (((p.x * 73856093) ^ (p.y * 19349663) ^ (p.z * 83492791)) % hash_size as i32) as usize
+fn hash(p: &Point3i, hash_size: i32) -> usize {
+    (((p.x * 73856093) ^ (p.y * 19349663) ^ (p.z * 83492791)) as u32 % hash_size as u32) as usize
 }
 
 /// **Main function** to **render** a scene multi-threaded (using all
@@ -382,7 +382,7 @@ pub fn render_sppm(
                             for y in p_min.y..p_max.y {
                                 for x in p_min.x..p_max.x {
                                     // add visible point to grid cell $(x, y, z)$
-                                    let h: usize = hash(&Point3i { x: x, y: y, z: z }, hash_size);
+                                    let h: usize = hash(&Point3i { x: x, y: y, z: z }, hash_size as i32);
                                     let mut node_arc: Arc<SPPMPixelListNode> =
                                         Arc::new(SPPMPixelListNode::default());
                                     let pixel_clone: Arc<SPPMPixel> = pixel.clone();
@@ -471,8 +471,9 @@ pub fn render_sppm(
                                         &grid_res,
                                         &mut photon_grid_index,
                                     ) {
-                                        let h: usize = hash(&photon_grid_index, hash_size);
+                                        let h: usize = hash(&photon_grid_index, hash_size as i32);
                                         // add photon contribution to visible points in _grid[h]_
+                                        assert!(h < hash_size, "hash({:?}, {:?})", photon_grid_index, hash_size);
                                         if let Some(root) = grid[h].get() {
                                             let mut node: &SPPMPixelListNode = root;
                                             loop {