Add sphere and quad intersection logic

Homework3/solution.go

@@ -44,7 +44,7 @@ func NewSphere(origin geom.Vector, r float64) Sphere {
 }
 
 func (triangle Triangle) Intersect(ray geom.Ray) bool {
-	// Find vectors for two edges sharing vertex 0
+	// Find vectors for two edges sharing the first vertex
 	edge1 := geom.Sub(triangle.b, triangle.a)
 	edge2 := geom.Sub(triangle.c, triangle.a)
 
@@ -85,9 +85,20 @@ func (triangle Triangle) Intersect(ray geom.Ray) bool {
 }
 
 func (quad Quad) Intersect(ray geom.Ray) bool {
-	return true
+	firstTriangle := Triangle{a: quad.a, b: quad.b, c: quad.c}
+	secondTriangle := Triangle{a: quad.a, b: quad.c, c: quad.d}
+
+	return firstTriangle.Intersect(ray) || secondTriangle.Intersect(ray)
 }
 
 func (sphere Sphere) Intersect(ray geom.Ray) bool {
+	L := geom.Sub(sphere.origin, ray.Origin)
+	tc := geom.Dot(L, ray.Direction)
+
+	d := geom.Dot(L, L) - (tc * tc)
+	if d > sphere.r {
+		return false
+	}
+
 	return true
 }

Homework3/solution_test.go

@@ -6,7 +6,7 @@ import (
 	"github.com/fmi/go-homework/geom"
 )
 
-func TestSampleSimpleOperations(t *testing.T) {
+func TestSampleSimpleTriangle(t *testing.T) {
 	var prim geom.Intersectable
 
 	a, b, c := geom.NewVector(-1, -1, 0), geom.NewVector(1, -1, 0), geom.NewVector(0, 1, 0)
@@ -18,6 +18,30 @@ func TestSampleSimpleOperations(t *testing.T) {
 	}
 }
 
+func TestSampleSimpleSphere(t *testing.T) {
+	var prim geom.Intersectable
+
+	origin, r := geom.NewVector(0, 0, 0), 2.0
+	prim = NewSphere(origin, r)
+	ray := geom.NewRay(geom.NewVector(0, 0, 2.5), geom.NewVector(0, 0, 0))
+
+	if !prim.Intersect(ray) {
+		t.Errorf("Expected ray %#v to intersect sphere %#v but it did not.", ray, prim)
+	}
+}
+
+func TestSampleSimpleQuad(t *testing.T) {
+	var prim geom.Intersectable
+
+	a, b, c, d := geom.NewVector(0, -2, 0), geom.NewVector(3, 0, 0), geom.NewVector(0, 1, 0), geom.Vector{-1, 0, 0}
+	prim = NewQuad(a, b, c, d)
+	ray := geom.Ray{geom.NewVector(0, 0, 2), geom.NewVector(0, 0, -1)}
+
+	if !prim.Intersect(ray) {
+		t.Errorf("Expected ray %#v to intersect quad %#v but it did not.", ray, prim)
+	}
+}
+
 func TestSampleIntersectableImplementations(t *testing.T) {
 	var prim geom.Intersectable