Instrument code to count ray/node tests during BVH traversal.

src/accel/bvh.rs

@@ -13,6 +13,7 @@ use timer::Timer;
 
 use super::bvh_base::{BVHBase, BVHBaseNode, BVH_MAX_DEPTH};
 use super::ACCEL_TRAV_TIME;
+use super::ACCEL_NODE_RAY_TESTS;
 
 
 #[derive(Copy, Clone, Debug)]
@@ -80,6 +81,7 @@ impl<'a> BVH<'a> {
 
         let mut timer = Timer::new();
         let mut trav_time: f64 = 0.0;
+        let mut node_tests: u64 = 0;
 
         let ray_sign = [
             rays[0].dir_inv.x() >= 0.0,
@@ -93,6 +95,7 @@ impl<'a> BVH<'a> {
         let mut stack_ptr = 1;
 
         while stack_ptr > 0 {
+            node_tests += ray_i_stack[stack_ptr] as u64;
             match node_stack[stack_ptr] {
                 &BVHNode::Internal {
                     children,
@@ -152,6 +155,10 @@ impl<'a> BVH<'a> {
             let v = att.get();
             att.set(v + trav_time);
         });
+        ACCEL_NODE_RAY_TESTS.with(|anv| {
+            let v = anv.get();
+            anv.set(v + node_tests);
+        });
     }
 
     fn construct_from_base(

src/accel/bvh4.rs

@@ -14,6 +14,7 @@ use timer::Timer;
 use bvh_order::{TRAVERSAL_TABLE, SplitAxes, calc_traversal_code};
 use super::bvh_base::{BVHBase, BVHBaseNode, BVH_MAX_DEPTH};
 use super::ACCEL_TRAV_TIME;
+use super::ACCEL_NODE_RAY_TESTS;
 
 
 #[derive(Copy, Clone, Debug)]
@@ -79,6 +80,7 @@ impl<'a> BVH4<'a> {
 
         let mut timer = Timer::new();
         let mut trav_time: f64 = 0.0;
+        let mut node_tests: u64 = 0;
 
         let traversal_table = {
             let ray_sign_is_neg = [
@@ -97,6 +99,7 @@ impl<'a> BVH4<'a> {
         let mut stack_ptr = 1;
 
         while stack_ptr > 0 {
+            node_tests += ray_i_stack[stack_ptr] as u64;
             match node_stack[stack_ptr] {
                 &BVH4Node::Inner {
                     traversal_code,
@@ -195,6 +198,10 @@ impl<'a> BVH4<'a> {
             let v = att.get();
             att.set(v + trav_time);
         });
+        ACCEL_NODE_RAY_TESTS.with(|anv| {
+            let v = anv.get();
+            anv.set(v + node_tests);
+        });
     }
 
     fn construct_from_base(

src/accel/mod.rs

@@ -18,6 +18,7 @@ pub use self::light_array::LightArray;
 // Track BVH traversal time
 thread_local! {
     pub static ACCEL_TRAV_TIME: Cell<f64> = Cell::new(0.0);
+    pub static ACCEL_NODE_RAY_TESTS: Cell<u64> = Cell::new(0);
 }
 
 pub trait LightAccel {

src/main.rs

@@ -316,6 +316,7 @@ fn main() {
                         "\t\t\tTraversal:            {:.3}s",
                         ntime * rstats.accel_traversal_time
                     );
+                    println!("\t\t\tRay/node tests:       {}", rstats.accel_node_visits);
                     println!(
                         "\t\tInitial ray generation: {:.3}s",
                         ntime * rstats.initial_ray_generation_time

src/renderer.rs

@@ -10,7 +10,7 @@ use scoped_threadpool::Pool;
 
 use halton;
 
-use accel::ACCEL_TRAV_TIME;
+use accel::{ACCEL_TRAV_TIME, ACCEL_NODE_RAY_TESTS};
 use algorithm::partition_pair;
 use color::{Color, XYZ, SpectralSample, map_0_1_to_wavelength};
 use float4::Float4;
@@ -40,6 +40,7 @@ pub struct Renderer<'a> {
 pub struct RenderStats {
     pub trace_time: f64,
     pub accel_traversal_time: f64,
+    pub accel_node_visits: u64,
     pub initial_ray_generation_time: f64,
     pub ray_generation_time: f64,
     pub sample_writing_time: f64,
@@ -51,6 +52,7 @@ impl RenderStats {
         RenderStats {
             trace_time: 0.0,
             accel_traversal_time: 0.0,
+            accel_node_visits: 0,
             initial_ray_generation_time: 0.0,
             ray_generation_time: 0.0,
             sample_writing_time: 0.0,
@@ -61,6 +63,7 @@ impl RenderStats {
     fn collect(&mut self, other: RenderStats) {
         self.trace_time += other.trace_time;
         self.accel_traversal_time += other.accel_traversal_time;
+        self.accel_node_visits += other.accel_node_visits;
         self.initial_ray_generation_time += other.initial_ray_generation_time;
         self.ray_generation_time += other.ray_generation_time;
         self.sample_writing_time += other.sample_writing_time;
@@ -341,6 +344,10 @@ impl<'a> Renderer<'a> {
             stats.accel_traversal_time = att.get();
             att.set(0.0);
         });
+        ACCEL_NODE_RAY_TESTS.with(|anv| {
+            stats.accel_node_visits = anv.get();
+            anv.set(0);
+        });
 
         // Collect stats
         collected_stats.write().unwrap().collect(stats);