Add Acceleration Structure Interface

ray-tracing-scene/src/util.rs

@@ -0,0 +1,43 @@
+use ray_tracing_core::prelude::*;
+
+pub fn triangle_intersection(ray: Ray, v: [Pos3; 3]) -> Option<Float> {
+    let e1 = v[1] - v[0];
+    let e2 = v[2] - v[0];
+
+    let ray_cross_e2 = Dir3::cross(ray.dir(), e2);
+    let det = e1.dot(ray_cross_e2);
+
+    if det > -f32::EPSILON && det < f32::EPSILON {
+        return None; // This ray is parallel to this triangle.
+    }
+
+    let inv_det = 1.0 / det;
+    let s = ray.start() - v[0];
+    let u = inv_det * s.dot(ray_cross_e2);
+    if !(0.0..=1.0).contains(&u) {
+        return None;
+    }
+
+    let s_cross_e1 = s.cross(e1);
+    let v = inv_det * Dir3::dot(ray.dir(), s_cross_e1);
+    if v < 0.0 || u + v > 1.0 {
+        return None;
+    }
+    // At this stage we can compute t to find out where the intersection point is on the line.
+    let t = inv_det * e2.dot(s_cross_e1);
+
+    if t > Float::EPSILON {
+        // ray intersection
+        Some(t)
+    } else {
+        // This means that there is a line intersection but not a ray intersection.
+        None
+    }
+}
+
+pub fn triangle_normal(v: [Pos3; 3]) -> Dir3 {
+    let e1 = v[1] - v[0];
+    let e2 = v[2] - v[0];
+
+    Dir3::cross(e1, e2)
+}