Hit function return hit struct

1 files changed, 43 insertions, 10 deletions

diff --git a/shaders/compute.comp b/shaders/compute.comp
index 1f901dc..b9c165e 100644
--- a/shaders/compute.comp
+++ b/shaders/compute.comp
@@ -3,6 +3,22 @@ struct ray {
     vec3 direction;
 };
 
+struct hit_info {
+    float t;
+    vec3 point;
+    vec3 normal;
+    bool front_face;
+};
+
+struct sphere {
+    vec4 position;
+    float radius;
+};
+
+vec3 at(ray r, float t) {
+    return r.origin + r.direction * t;
+}
+
 layout(set = 0, binding = 0) buffer Inputs {
     vec4 sky_color;
     vec4 ground_color;
@@ -13,21 +29,33 @@ layout(set = 0, binding = 0) buffer Inputs {
     float proj_plane_distance;
     float padding;
 
-    vec4 sphere_position;
+    sphere s;
 
-    vec4 [] image;
+    vec4[] image;
 };
 
-bool hit_sphere(vec3 position, float radius, ray r) {
+bool hit_sphere(ray r, out hit_info info) {
     // Vector from the ray origin to sphere position
-    vec3 origin_center = r.origin - position;
+    vec3 origin_center = r.origin - s.position.xyz;
 
     float a = dot(r.direction, r.direction);
     float half_b = dot(r.direction, origin_center);
-    float c = dot(origin_center, origin_center) - radius * radius;
+    float c = dot(origin_center, origin_center) - s.radius * s.radius;
     float discriminant = half_b * half_b - a * c;
 
-    return (discriminant > 0);
+    if (discriminant < 0) {
+        info.t = -1.0;
+        return false;
+    }
+
+    info.t = (-half_b - sqrt(discriminant)) / a;
+    info.point = at(r, info.t);
+
+    vec3 outward_normal = (info.point - s.position.xyz) / s.radius;
+    info.front_face = dot(outward_normal, r.direction) < 0.0;
+    info.normal = info.front_face ? outward_normal : -outward_normal;
+
+    return true;
 }
 
 void main() {
@@ -36,16 +64,21 @@ void main() {
     uint width = gl_NumWorkGroups.x;
     uint height = gl_NumWorkGroups.y;
 
-    vec2 uv = vec2(float(x) / (width - 1), float(y) / (height - 1));
+    vec2 uv = vec2(float(x) / (width - 1), 1.0 - (float(y) / (height - 1)));
 
     vec3 first = camera_pos.xyz - vec3(viewport_width / 2.0, viewport_height / 2.0, proj_plane_distance);
     vec3 proj_plane_pos = first + vec3(uv.x * viewport_width, uv.y * viewport_height, 0.0);
 
     ray r = ray(camera_pos.xyz, proj_plane_pos - camera_pos.xyz);
-    if (hit_sphere(sphere_position.xyz, 0.5, r)) {
-        image[y * width + x] = vec4(1.0, 0.0, 0.0, 0.0);
+    hit_info info;
+
+    if (hit_sphere(r, info)) {
+        vec3 hit_normal = normalize(info.normal);
+        hit_normal = (hit_normal + 1.0) * 0.5;
+
+        image[y * width + x] = vec4(hit_normal, 0.0);
         return;
     }
 
-    image[y * width + x] = mix(sky_color, ground_color, uv.y);
+    image[y * width + x] = mix(ground_color, sky_color, uv.y);
 }