Chap 15: triangles

fremag · Jan 27, 2024 · 911d04c · 911d04c
1 parent 5923007
commit 911d04c
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Showing 2 changed files with 73 additions and 6 deletions.
diff --git a/src/shapes/triangle.rs b/src/shapes/triangle.rs
@@ -1,4 +1,5 @@
 use crate::core::bounds::Bounds;
+use crate::core::math;
 use crate::core::math::Float;
 use crate::core::ray::Ray;
 use crate::core::tuple::Tuple;
@@ -23,19 +24,43 @@ impl Triangle {
     pub fn new(p1 : Tuple, p2 : Tuple, p3 : Tuple) -> Self {
         let e1 = p2-p1;
         let e2 = p3-p1;
-        let normal = e2 * &e1;
+        let normal = (e2 * &e1).normalize();
         Self {p1, p2, p3, e1, e2, normal}
     }
 
-    pub(crate) fn intersect(&self, point: &Ray) -> Vec<Float> {
-        todo!()
+    pub(crate) fn intersect(&self, ray: &Ray) -> Vec<Float> {
+        let dir_cross_e2 = ray.direction * &self.e2;
+        let det = self.e1.dot(&dir_cross_e2);
+        if det.abs() < math::EPSILON {
+            return vec![];
+        }
+        let f = 1.0 / det;
+        let p1_to_origin = ray.origin - self.p1;
+        let u = f * p1_to_origin.dot(&dir_cross_e2);
+        if u < 0.0 || u > 1.0 {
+            return vec![];
+        }
+
+        let origin_cross_e1 = p1_to_origin * &self.e1;
+        let v = f * ray.direction.dot(&origin_cross_e1);
+        if v < 0.0 || (u + v) > 1.0 {
+            return vec![];
+        }
+
+        let t = f * self.e2.dot(&origin_cross_e1);
+        return vec![t]
     }
 
     pub(crate) fn normal_at(&self, _: &Tuple) -> Tuple {
         self.normal
     }
 
     pub(crate) fn bounds(&self) -> Bounds {
-        todo!()
+        let mut bounds = Bounds::new();
+        bounds.add(&self.p1);
+        bounds.add(&self.p2);
+        bounds.add(&self.p3);
+
+        bounds
     }
 }
diff --git a/src/tests/triangle_tests.rs b/src/tests/triangle_tests.rs
@@ -1,5 +1,6 @@
 #[cfg(test)]
 mod tests {
+    use crate::core::ray::ray;
     use crate::core::tuple::{point, vector};
     use crate::shapes::triangle::Triangle;
 
@@ -11,8 +12,8 @@ mod tests {
         let t = Triangle::new(p1, p2, p3);
 
         assert_eq!(t.p1, point(0.0, 1.0, 0.0));
-        assert_eq!(t.p1, point(-1.0, 0.0, 0.0));
-        assert_eq!(t.p1, point(1.0, 0.0, 0.0));
+        assert_eq!(t.p2, point(-1.0, 0.0, 0.0));
+        assert_eq!(t.p3, point(1.0, 0.0, 0.0));
 
         assert_eq!(t.e1, vector(-1.0, -1.0, 0.0));
         assert_eq!(t.e2, vector(1.0, -1.0, 0.0));
@@ -29,4 +30,45 @@ mod tests {
         assert_eq!(n2, t.normal);
         assert_eq!(n3, t.normal);
     }
+
+    #[test]
+    fn intersecting_a_ray_parallel_to_the_triangle_test() {
+        let t = Triangle::new(point(0.0, 1.0, 0.0), point(-1.0, 0.0, 0.0), point(1.0, 0.0, 0.0));
+        let r = ray(point(0.0, -1.0, -2.0), vector(0.0, 1.0, 0.0));
+        let xs = t.intersect(&r);
+        assert!(xs.is_empty());
+    }
+
+    #[test]
+    fn a_ray_misses_the_p1_p3_edge_test() {
+        let t = Triangle::new(point(0.0, 1.0, 0.0), point(-1.0, 0.0, 0.0), point(1.0, 0.0, 0.0));
+        let r = ray(point(1.0, 1.0, -2.0), vector(0.0, 0.0, 1.0));
+        let xs = t.intersect(&r);
+        assert!(xs.is_empty());
+    }
+
+    #[test]
+    fn a_ray_misses_the_p1_p2_edge_test() {
+        let t = Triangle::new(point(0.0, 1.0, 0.0), point(-1.0, 0.0, 0.0), point(1.0, 0.0, 0.0));
+        let r = ray(point(-1.0, 1.0, -2.0), vector(0.0, 0.0, 1.0));
+        let xs = t.intersect(&r);
+        assert!(xs.is_empty());
+    }
+
+    #[test]
+    fn a_ray_misses_the_p2_p3_edge_test() {
+        let t = Triangle::new(point(0.0, 1.0, 0.0), point(-1.0, 0.0, 0.0), point(1.0, 0.0, 0.0));
+        let r = ray(point(0.0, -1.0, -2.0), vector(0.0, 0.0, 1.0));
+        let xs = t.intersect(&r);
+        assert!(xs.is_empty());
+    }
+
+    #[test]
+    fn a_ray_strikes_a_triangle_test() {
+        let t = Triangle::new(point(0.0, 1.0, 0.0), point(-1.0, 0.0, 0.0), point(1.0, 0.0, 0.0));
+        let r = ray(point(0.0, 0.5, -2.0), vector(0.0, 0.0, 1.0));
+        let xs = t.intersect(&r);
+        assert_eq!(xs.len(), 1);
+        assert_eq!(xs[0], 2.0);
+    }
 }