From be5f1133bff5d4c551e2702211acb155d8819fd0 Mon Sep 17 00:00:00 2001
From: ladevieq <ladevie.quentin@gmail.com>
Date: Mon, 29 Mar 2021 22:25:29 +0200
Subject: BVH simple implementation

---
 shaders/compute.comp | 59 +++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 5 deletions(-)

(limited to 'shaders')

diff --git a/shaders/compute.comp b/shaders/compute.comp
index 3510d52..6f35094 100644
--- a/shaders/compute.comp
+++ b/shaders/compute.comp
@@ -27,18 +27,19 @@ struct hit_info {
     bool front_face;
 };
 
+struct aabb {
+    vec4 min;
+    vec4 max;
+};
+
 struct sphere {
     vec4 position;
     material mat;
+    aabb bb;
     float radius;
     float[3] padding;
 };
 
-struct aabb {
-    vec4 min;
-    vec4 max;
-};
-
 struct camera {
     vec4 position;
 
@@ -54,6 +55,14 @@ struct camera {
     float[3] padding;
 };
 
+struct bvh_node {
+    aabb bb;
+    int left;
+    int right;
+    int sphere_id;
+    uint padding;
+};
+
 layout(set = 0, binding = 0) buffer Inputs {
     vec4 sky_color;
     vec4 ground_color;
@@ -64,6 +73,7 @@ layout(set = 0, binding = 0) buffer Inputs {
     vec4[1000] random_in_sphere;
 
     sphere[512] spheres;
+    bvh_node[1024] nodes;
 
     uint max_bounce;
     uint samples_per_pixel;
@@ -116,6 +126,45 @@ bool hit_aabb(aabb b, ray r, float min_t, float max_t) {
     return true;
 }
 
+bool hit_node(bvh_node node, ray r, float min_t, float max_t, out hit_info info) {
+    if (!hit_aabb(node.bb, r, min_t, max_t)) {
+        return false;
+    }
+
+    int stack_id = -1;
+    int stack[64];
+    bvh_node current_node = node;
+
+    while(true) {
+        bool hit_left = hit_aabb(nodes[current_node.left - 1].bb, r, min_t, max_t);
+        bool hit_right = hit_aabb(nodes[current_node.right - 1].bb, r, min_t, max_t);
+
+        if (hit_left && hit_right) {
+            stack_id++;
+            stack[stack_id] = current_node.left - 1;
+
+            current_node = nodes[current_node.right - 1];
+        } else if (hit_left) {
+            current_node = nodes[current_node.left - 1];
+        } else if (hit_right) {
+            current_node = nodes[current_node.right - 1];
+        } else {
+            if (stack_id >= 0) {
+                current_node = nodes[stack[stack_id]];
+                stack_id--;
+            } else {
+                return false;
+            }
+        }
+
+        // Reached a leaf
+        if (current_node.left == -1 && current_node.right == -1) {
+            return true;
+        }
+    }
+
+}
+
 bool hit_sphere(sphere s, ray r, float min_t, float max_t, out hit_info info) {
     vec3 origin_center = r.origin - s.position.xyz;
 
-- 
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