refactor

README.md

@@ -13,11 +13,10 @@ This is a CPU-only [path tracing](http://en.wikipedia.org/wiki/Path_tracing) eng
 * Supports OBJ, Binary STL and ASCII STL
 * Supports textures, bump maps and normal maps
 * Supports volume rendering from image slices
-* Uses k-d trees to accelerate ray intersection tests
 * Supports various material properties
-* Light sources with configurable attenuation
 * Supports configurable depth of field
 * Supports iterative rendering
+* Uses k-d trees to accelerate ray intersection tests
 * Uses all CPU cores in parallel
 
 ### TODO

examples/beads.go

@@ -40,7 +40,7 @@ func frame(path string, t float64) {
 			scene.Add(sphere)
 		}
 	}
-	scene.Add(NewSphere(V(4, 4, 20), 2, LightMaterial(HexColor(0xFFFFFF), 30, NoAttenuation)))
+	scene.Add(NewSphere(V(4, 4, 20), 2, LightMaterial(HexColor(0xFFFFFF), 30)))
 	fovy := 40.0
 	camera := LookAt(eye, center, up, fovy)
 	sampler := NewSampler(4, 4)

examples/bunny.go

@@ -14,8 +14,8 @@ func main() {
 	scene.Add(mesh)
 	floor := GlossyMaterial(HexColor(0x33332D), 1.2, Radians(20))
 	scene.Add(NewCube(V(-10000, -10000, -10000), V(10000, 0, 10000), floor))
-	scene.Add(NewSphere(V(0, 5, 0), 1, LightMaterial(Color{1, 1, 1}, 20, NoAttenuation)))
-	scene.Add(NewSphere(V(4, 5, 4), 1, LightMaterial(Color{1, 1, 1}, 20, NoAttenuation)))
+	scene.Add(NewSphere(V(0, 5, 0), 1, LightMaterial(Color{1, 1, 1}, 20)))
+	scene.Add(NewSphere(V(4, 5, 4), 1, LightMaterial(Color{1, 1, 1}, 20)))
 	camera := LookAt(V(-1, 2, 3), V(0, 0.75, 0), V(0, 1, 0), 50)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/cornell.go

@@ -6,7 +6,7 @@ func main() {
 	white := DiffuseMaterial(Color{0.740, 0.742, 0.734})
 	red := DiffuseMaterial(Color{0.366, 0.037, 0.042})
 	green := DiffuseMaterial(Color{0.163, 0.409, 0.083})
-	light := LightMaterial(Color{0.780, 0.780, 0.776}, 20, NoAttenuation)
+	light := LightMaterial(Color{0.780, 0.780, 0.776}, 20)
 	scene := Scene{}
 	n := 10.0
 	scene.Add(NewCube(V(-n, -11, -n), V(n, -10, n), white))

examples/counties.go

@@ -61,7 +61,7 @@ func LoadTriangles(path string) []*Triangle {
 func main() {
 	rand.Seed(6)
 	floor := GlossyMaterial(HexColor(0xFCFFF5), 1.5, Radians(20))
-	light := LightMaterial(HexColor(0xFFFFFF), 1, QuadraticAttenuation(0.002))
+	light := LightMaterial(HexColor(0xFFFFFF), 1)
 	triangles := LoadTriangles("examples/counties.csv")
 	mesh := NewMesh(triangles)
 	mesh.FitInside(Box{V(-1, -1, 0), V(1, 1, 1)}, V(0.5, 0.5, 0))

examples/cube.go

@@ -34,7 +34,7 @@ func main() {
 			scene.Add(NewTransformedShape(meshes[rand.Intn(len(meshes))], Translate(Vector{fx, fy - 1, fz})))
 		}
 	}
-	scene.Add(NewSphere(Vector{8, 10, 0}, 3, LightMaterial(Color{1, 1, 1}, 30, NoAttenuation)))
+	scene.Add(NewSphere(Vector{8, 10, 0}, 3, LightMaterial(Color{1, 1, 1}, 30)))
 	camera := LookAt(Vector{-10, 10, 0}, Vector{-2, 0, 0}, Vector{0, 1, 0}, 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/cylinder.go

@@ -34,7 +34,7 @@ func main() {
 			scene.Add(NewTransformedShape(mesh, Translate(Vector{fx, fy, fz})))
 		}
 	}
-	scene.Add(NewSphere(Vector{1, 0, 10}, 3, LightMaterial(Color{1, 1, 1}, 20, NoAttenuation)))
+	scene.Add(NewSphere(Vector{1, 0, 10}, 3, LightMaterial(Color{1, 1, 1}, 20)))
 	camera := LookAt(Vector{-5, 0, 5}, Vector{1, 0, 0}, Vector{0, 0, 1}, 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/dragon.go

@@ -17,7 +17,7 @@ func main() {
 	scene.Add(mesh)
 	floor := GlossyMaterial(HexColor(0xD8CAA8), 1.2, Radians(20))
 	scene.Add(NewCube(Vector{-1000, -1000, -1000}, Vector{1000, 0, 1000}, floor))
-	scene.Add(NewSphere(Vector{0, 10, 0}, 1, LightMaterial(Color{1, 1, 1}, 20, NoAttenuation)))
+	scene.Add(NewSphere(Vector{0, 10, 0}, 1, LightMaterial(Color{1, 1, 1}, 20)))
 	camera := LookAt(Vector{-3, 2, -1}, Vector{0, 0.5, 0}, Vector{0, 1, 0}, 35)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/4, 1080/4, -1)

examples/ellipsoid.go

@@ -5,7 +5,7 @@ import . "github.com/fogleman/pt/pt"
 func main() {
 	scene := Scene{}
 	wall := GlossyMaterial(HexColor(0xFCFAE1), 1.333, Radians(30))
-	scene.Add(NewSphere(Vector{10, 10, 10}, 2, LightMaterial(Color{1, 1, 1}, 50, NoAttenuation)))
+	scene.Add(NewSphere(Vector{10, 10, 10}, 2, LightMaterial(Color{1, 1, 1}, 50)))
 	scene.Add(NewCube(Vector{-100, -100, -100}, Vector{-12, 100, 100}, wall))
 	scene.Add(NewCube(Vector{-100, -100, -100}, Vector{100, -1, 100}, wall))
 	material := GlossyMaterial(HexColor(0x167F39), 1.333, Radians(30))

examples/example1.go

@@ -4,15 +4,16 @@ import . "github.com/fogleman/pt/pt"
 
 func main() {
 	scene := Scene{}
-	scene.Add(NewSphere(V(1.5, 1.25, 0), 1.25, SpecularMaterial(HexColor(0x334D5C), 1.3)))
-	scene.Add(NewSphere(V(-1, 1, 2), 1, SpecularMaterial(HexColor(0xEFC94C), 1.3)))
-	scene.Add(NewSphere(V(-2.5, 0.75, 0), 0.75, SpecularMaterial(HexColor(0xEFC94C), 10000)))
-	scene.Add(NewSphere(V(-0.75, 0.75, -1), 0.5, TransparentMaterial(Color{}, 1.333, 0, 0)))
-	scene.Add(NewCube(V(-100, -1, -100), V(100, 0, 100), DiffuseMaterial(Color{1, 1, 1})))
-	scene.Add(NewSphere(V(-1.5, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 100, LinearAttenuation(1))))
-	// scene.Add(NewSphere(V(0, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 100, LinearAttenuation(1))))
-	// scene.Add(NewSphere(V(1.5, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 100, LinearAttenuation(1))))
-	camera := LookAt(V(0, 2, -5), V(0, 0, 3), V(0, 1, 0), 45)
-	sampler := NewSampler(4, 4)
+	scene.Add(NewSphere(V(1.5, 1.25, 0), 1.25, SpecularMaterial(HexColor(0x004358), 1.2)))
+	scene.Add(NewSphere(V(-1, 1, 2), 1, SpecularMaterial(HexColor(0xFFE11A), 1.2)))
+	scene.Add(NewSphere(V(-2.5, 0.75, 0), 0.75, SpecularMaterial(HexColor(0xFD7400), 1.2)))
+	scene.Add(NewSphere(V(-0.75, 0.5, -1), 0.5, SpecularMaterial(HexColor(0xBEDB39), 1.2)))
+	scene.Add(NewCube(V(-100, -1, -100), V(100, 0, 100), GlossyMaterial(Color{1, 1, 1}, 1.1, Radians(10))))
+	scene.Add(NewSphere(V(-1.5, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 30)))
+	// scene.Add(NewSphere(V(0, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 50)))
+	// scene.Add(NewSphere(V(1.5, 4, 0), 0.5, LightMaterial(Color{1, 1, 1}, 50)))
+	camera := LookAt(V(0, 2.5, -5), V(0, 0, 3), V(0, 1, 0), 45)
+	camera.SetFocus(V(-0.75, 1, -1), 0.15)
+	sampler := NewSampler(4, 8)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)
 }

examples/example2.go

@@ -13,7 +13,7 @@ func main() {
 		}
 	}
 	scene.Add(NewCube(V(-100, -1, -100), V(100, 0, 100), whiteMat))
-	scene.Add(NewSphere(V(-1, 4, -1), 1, LightMaterial(Color{1, 1, 1}, 30, NoAttenuation)))
+	scene.Add(NewSphere(V(-1, 4, -1), 1, LightMaterial(Color{1, 1, 1}, 30)))
 	camera := LookAt(V(0, 4, -8), V(0, 0, -2), V(0, 1, 0), 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/example3.go

@@ -17,7 +17,7 @@ func main() {
 			scene.Add(NewCube(min, max, material))
 		}
 	}
-	scene.Add(NewCube(V(-5, 10, -5), V(5, 11, 5), LightMaterial(Color{1, 1, 1}, 20, QuadraticAttenuation(0.05))))
+	scene.Add(NewCube(V(-5, 10, -5), V(5, 11, 5), LightMaterial(Color{1, 1, 1}, 5)))
 	camera := LookAt(V(20, 10, 0), V(8, 0, 0), V(0, 1, 0), 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/gopher.go

@@ -8,7 +8,7 @@ func main() {
 	// create materials
 	gopher := GlossyMaterial(Color{}, 1.2, Radians(30))
 	wall := GlossyMaterial(HexColor(0xFCFAE1), 1.5, Radians(10))
-	light := LightMaterial(Color{1, 1, 1}, 80, NoAttenuation)
+	light := LightMaterial(Color{1, 1, 1}, 80)
 
 	// add walls and lights
 	scene.Add(NewCube(V(-10, -1, -10), V(-2, 10, 10), wall))

examples/hits.go

@@ -5,7 +5,7 @@ import . "github.com/fogleman/pt/pt"
 func main() {
 	scene := Scene{}
 	material := DiffuseMaterial(Color{0.95, 0.95, 1})
-	light := LightMaterial(Color{1, 1, 1}, 1300, LinearAttenuation(1))
+	light := LightMaterial(Color{1, 1, 1}, 300)
 	scene.Add(NewSphere(Vector{-0.75, -0.75, 5}, 0.25, light))
 	scene.Add(NewCube(Vector{-1000, -1000, -1000}, Vector{1000, 1000, 0}, material))
 	mesh, err := LoadSTL("examples/hits.stl", material)

examples/love.go

@@ -13,9 +13,9 @@ func main() {
 	}
 	mesh.FitInside(Box{Vector{-0.5, 0, -0.5}, Vector{0.5, 1, 0.5}}, Vector{0.5, 0, 0.5})
 	scene.Add(mesh)
-	scene.Add(NewSphere(Vector{-2, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30, NoAttenuation)))
-	scene.Add(NewSphere(Vector{0, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30, NoAttenuation)))
-	scene.Add(NewSphere(Vector{2, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30, NoAttenuation)))
+	scene.Add(NewSphere(Vector{-2, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30)))
+	scene.Add(NewSphere(Vector{0, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30)))
+	scene.Add(NewSphere(Vector{2, 10, 2}, 1, LightMaterial(Color{1, 1, 1}, 30)))
 	camera := LookAt(Vector{0, 1.5, 2}, Vector{0, 0.5, 0}, Vector{0, 1, 0}, 35)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/materials.go

@@ -26,7 +26,7 @@ func main() {
 	scene.Add(NewSphere(V(0, 1.5, -4), 1.5, material))
 
 	scene.Add(NewCube(V(-1000, -1, -1000), V(1000, 0, 1000), GlossyMaterial(HexColor(0xFFFFFF), 1.4, Radians(20))))
-	scene.Add(NewSphere(V(0, 5, 0), 1, LightMaterial(Color{1, 1, 1}, 50, LinearAttenuation(0.4))))
+	scene.Add(NewSphere(V(0, 5, 0), 1, LightMaterial(Color{1, 1, 1}, 25)))
 	camera := LookAt(V(0, 3, 6), V(0, 1, 0), V(0, 1, 0), 30)
 	sampler := NewSampler(16, 16)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/maze.go

@@ -22,8 +22,7 @@ func main() {
 			}
 		}
 	}
-	a := NoAttenuation // QuadraticAttenuation(0.25)
-	scene.Add(NewSphere(V(0, 0, 2.25), 0.25, LightMaterial(Color{1, 1, 1}, 500, a)))
+	scene.Add(NewSphere(V(0, 0, 2.25), 0.25, LightMaterial(Color{1, 1, 1}, 500)))
 	camera := LookAt(V(1, 0, 30), V(0, 0, 0), V(0, 0, 1), 35)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/noise.go

@@ -26,7 +26,7 @@ func main() {
 			}
 		}
 	}
-	light := NewSphere(V(100, 0, 50), 5, LightMaterial(Color{1, 1, 1}, 300, NoAttenuation))
+	light := NewSphere(V(100, 0, 50), 5, LightMaterial(Color{1, 1, 1}, 300))
 	scene.Add(light)
 	camera := LookAt(V(0, 0, -20), V(0, 0, 0), V(0, 1, 0), 30)
 	sampler := NewSampler(4, 4)

examples/qbert.go

@@ -27,7 +27,7 @@ func main() {
 		}
 	}
 	scene.Add(NewCube(V(-1000, -1000, -1), V(1000, 1000, 0), floor))
-	scene.Add(NewSphere(V(fn, fn/3, fn*2), 1, LightMaterial(Color{1, 1, 1}, 100, NoAttenuation)))
+	scene.Add(NewSphere(V(fn, fn/3, fn*2), 1, LightMaterial(Color{1, 1, 1}, 100)))
 	camera := LookAt(V(fn*2, fn*2, fn*2), V(0, 0, fn/4), V(0, 0, 1), 35)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/spheres-anim.go

@@ -102,7 +102,7 @@ func frame(i int) {
 	scene := Scene{}
 	scene.Color = HexColor(0xFFFFFF)
 	sphere(&scene, Vector{}, Vector{}, 1, 0, 7, t)
-	scene.Add(NewSphere(Vector{0, 0, 6}, 0.5, LightMaterial(Color{1, 1, 1}, 1, NoAttenuation)))
+	scene.Add(NewSphere(Vector{0, 0, 6}, 0.5, LightMaterial(Color{1, 1, 1}, 1)))
 	camera := LookAt(Vector{x, y, 1}, Vector{0, 0, 0}, Vector{0, 0, 1}, 30)
 	template := fmt.Sprintf("out%03d.png", i)
 	// IterativeRender(template, 1, &scene, &camera, 1920, 1080, 16, 16, 4)

examples/spheres.go

@@ -49,7 +49,7 @@ func main() {
 	scene := Scene{}
 	scene.Color = HexColor(0xFFFFFF)
 	sphere(&scene, Vector{}, Vector{}, 1, 8)
-	scene.Add(NewSphere(Vector{0, 0, 6}, 0.5, LightMaterial(Color{1, 1, 1}, 1, NoAttenuation)))
+	scene.Add(NewSphere(Vector{0, 0, 6}, 0.5, LightMaterial(Color{1, 1, 1}, 1)))
 	camera := LookAt(Vector{3, 1.75, 1}, Vector{0.75, 0.5, 0}, Vector{0, 0, 1}, 30)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/sponza.go

@@ -13,7 +13,7 @@ func main() {
 	}
 	mesh.MoveTo(Vector{}, Vector{0.5, 0, 0.5})
 	scene.Add(mesh)
-	scene.Add(NewSphere(Vector{0, 20, 0}, 3, LightMaterial(Color{1, 1, 1}, 100, NoAttenuation)))
+	scene.Add(NewSphere(Vector{0, 20, 0}, 3, LightMaterial(Color{1, 1, 1}, 100)))
 	camera := LookAt(Vector{-10, 2, 0}, Vector{0, 4, 0}, Vector{0, 1, 0}, 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/suzanne.go

@@ -5,8 +5,8 @@ import . "github.com/fogleman/pt/pt"
 func main() {
 	scene := Scene{}
 	material := DiffuseMaterial(HexColor(0x334D5C))
-	scene.Add(NewSphere(Vector{0.5, 1, 3}, 1, LightMaterial(Color{1, 1, 1}, 10, NoAttenuation)))
-	// scene.Add(NewSphere(Vector{1.5, 1, 3}, 1, LightMaterial(Color{1, 1, 1}, 10, NoAttenuation)))
+	scene.Add(NewSphere(Vector{0.5, 1, 3}, 1, LightMaterial(Color{1, 1, 1}, 10)))
+	// scene.Add(NewSphere(Vector{1.5, 1, 3}, 1, LightMaterial(Color{1, 1, 1}, 10)))
 	scene.Add(NewCube(Vector{-5, -5, -2}, Vector{5, 5, -1}, material))
 	mesh, err := LoadOBJ("examples/suzanne.obj", SpecularMaterial(HexColor(0xEFC94C), 1.3))
 	if err != nil {

examples/teapot.go

@@ -4,8 +4,8 @@ import . "github.com/fogleman/pt/pt"
 
 func main() {
 	scene := Scene{}
-	scene.Add(NewSphere(Vector{-2, 5, -3}, 0.5, LightMaterial(Color{1, 1, 1}, 50, NoAttenuation)))
-	scene.Add(NewSphere(Vector{5, 5, -3}, 0.5, LightMaterial(Color{1, 1, 1}, 50, NoAttenuation)))
+	scene.Add(NewSphere(Vector{-2, 5, -3}, 0.5, LightMaterial(Color{1, 1, 1}, 50)))
+	scene.Add(NewSphere(Vector{5, 5, -3}, 0.5, LightMaterial(Color{1, 1, 1}, 50)))
 	scene.Add(NewCube(Vector{-30, -1, -30}, Vector{30, 0, 30}, SpecularMaterial(HexColor(0xFCFAE1), 2)))
 	mesh, err := LoadOBJ("examples/teapot.obj", SpecularMaterial(HexColor(0xB9121B), 2))
 	if err != nil {

examples/toybrick.go

@@ -45,8 +45,6 @@ func main() {
 			}
 		}
 	}
-	// light := LightMaterial(Color{0.2, 0.2, 0.2}, 10, QuadraticAttenuation(0.01))
-	// scene.Add(NewSphere(Vector{0, 0, 25}, 1, light))
 	camera := LookAt(Vector{-23, 13, 20}, Vector{0, 0, 0}, Vector{0, 0, 1}, 45)
 	sampler := NewSampler(4, 4)
 	IterativeRender("out%03d.png", 1000, &scene, &camera, sampler, 1920/2, 1080/2, -1)

examples/volume.go

@@ -79,7 +79,7 @@ func main() {
 	// wall := GlossyMaterial(Color{1, 1, 1}, 1.1, Radians(20))
 	// scene.Add(NewCube(V(-10, 0.65, -10), V(10, 10, 10), wall))
 
-	// light := LightMaterial(Color{1, 1, 1}, 20, NoAttenuation)
+	// light := LightMaterial(Color{1, 1, 1}, 20)
 	// scene.Add(NewSphere(V(1, -5, -1), 1, light))
 
 	fmt.Println(volume.W, volume.H, volume.D)

pt/material.go

@@ -7,33 +7,32 @@ type Material struct {
 	BumpTexture    Texture
 	BumpMultiplier float64
 	Emittance      float64
-	Attenuation    Attenuation
 	Index          float64 // refractive index
 	Gloss          float64 // reflection cone angle in radians
 	Tint           float64 // specular and refractive tinting
 	Transparent    bool
 }
 
 func DiffuseMaterial(color Color) Material {
-	return Material{color, nil, nil, nil, 1, 0, NoAttenuation, 1, 0, 0, false}
+	return Material{color, nil, nil, nil, 1, 0, 1, 0, 0, false}
 }
 
 func SpecularMaterial(color Color, index float64) Material {
-	return Material{color, nil, nil, nil, 1, 0, NoAttenuation, index, 0, 0, false}
+	return Material{color, nil, nil, nil, 1, 0, index, 0, 0, false}
 }
 
 func GlossyMaterial(color Color, index, gloss float64) Material {
-	return Material{color, nil, nil, nil, 1, 0, NoAttenuation, index, gloss, 0, false}
+	return Material{color, nil, nil, nil, 1, 0, index, gloss, 0, false}
 }
 
 func ClearMaterial(index, gloss float64) Material {
-	return Material{Color{}, nil, nil, nil, 1, 0, NoAttenuation, index, gloss, 0, true}
+	return Material{Color{}, nil, nil, nil, 1, 0, index, gloss, 0, true}
 }
 
 func TransparentMaterial(color Color, index, gloss, tint float64) Material {
-	return Material{color, nil, nil, nil, 1, 0, NoAttenuation, index, gloss, tint, true}
+	return Material{color, nil, nil, nil, 1, 0, index, gloss, tint, true}
 }
 
-func LightMaterial(color Color, emittance float64, attenuation Attenuation) Material {
-	return Material{color, nil, nil, nil, 1, emittance, attenuation, 1, 0, 0, false}
+func LightMaterial(color Color, emittance float64) Material {
+	return Material{color, nil, nil, nil, 1, emittance, 1, 0, 0, false}
 }

pt/sampler.go

@@ -55,8 +55,7 @@ func (s *DefaultSampler) sample(scene *Scene, ray Ray, emission bool, samples, d
 		if s.DirectLighting && !emission {
 			return Color{}
 		}
-		attenuation := info.Material.Attenuation.Compute(hit.T)
-		result = result.Add(info.Color.MulScalar(emittance * attenuation * float64(samples)))
+		result = result.Add(info.Color.MulScalar(emittance * float64(samples)))
 	}
 	n := int(math.Sqrt(float64(samples)))
 	for u := 0; u < n; u++ {
@@ -126,7 +125,6 @@ func (s *DefaultSampler) directLight(scene *Scene, n Ray, rnd *rand.Rand) Color
 	material := light.MaterialAt(point)
 	color := light.ColorAt(point)
 	emittance := material.Emittance
-	attenuation := material.Attenuation.Compute(hit.T)
 
 	// compute solid angle (hemisphere coverage)
 	hyp := center.Sub(n.Origin).Length()
@@ -138,6 +136,6 @@ func (s *DefaultSampler) directLight(scene *Scene, n Ray, rnd *rand.Rand) Color
 	r := math.Sin(theta) * adj
 	coverage := (r * r) / (d * d)
 
-	m := diffuse * emittance * attenuation * coverage * float64(nLights)
+	m := diffuse * emittance * coverage * float64(nLights)
 	return color.MulScalar(m)
 }