From ac555beafc5aa25d76a328c1c866f99baae43141 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sun, 12 Feb 2023 13:47:29 -0800
Subject: [PATCH] rtiow: BVHTriangles use a fixed 100 divisions for split
 planes.

---
 rtiow/renderer/src/bvh_triangles.rs | 34 ++++++++++++++++-------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/rtiow/renderer/src/bvh_triangles.rs b/rtiow/renderer/src/bvh_triangles.rs
index 8833bd5..4b15359 100644
--- a/rtiow/renderer/src/bvh_triangles.rs
+++ b/rtiow/renderer/src/bvh_triangles.rs
@@ -219,27 +219,31 @@ where
     }
 
     fn find_best_split_plane(&self, node: &BVHNode) -> SplitCost {
-        let mut best_axis = usize::MAX;
-        let mut best_pos = 0.;
-        let mut best_cost = f32::MAX;
+        let mut best = SplitCost {
+            pos: 0.,
+            cost: f32::MAX,
+            axis: usize::MAX,
+        };
 
         for axis in 0..3 {
-            for i in 0..node.tri_count {
-                let triangle = &self.triangles[self.triangle_index[(node.left_first + i) as usize]];
-                let candidate_pos = triangle.centroid[axis];
+            let bounds_min = node.aabb.min()[axis];
+            let bounds_max = node.aabb.max()[axis];
+            if bounds_min == bounds_max {
+                continue;
+            }
+            let scale = (bounds_max - bounds_min) / 100.;
+
+            for i in 0..100 {
+                let candidate_pos = bounds_min + (i as f32) * scale;
                 let cost = self.evaluate_sah(node, axis, candidate_pos);
-                if cost <= best_cost {
-                    best_pos = candidate_pos;
-                    best_axis = axis;
-                    best_cost = cost;
+                if cost <= best.cost {
+                    best.pos = candidate_pos;
+                    best.axis = axis;
+                    best.cost = cost;
                 }
             }
         }
-        SplitCost {
-            pos: best_pos,
-            cost: best_cost,
-            axis: best_axis,
-        }
+        best
     }
 
     fn subdivide(&mut self, idx: usize) {