diff --git a/.gitignore b/.gitignore
index 2f71be50..240fbf0c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -302,3 +302,5 @@ CMakeSettings.json
 /imgui.ini
 /set_accel_kernel
 /results.txt
+
+/data/
diff --git a/cbox_diff/cbox-diff/cbox-diff-2.luisa b/cbox_diff/cbox-diff/cbox-diff-2.luisa
new file mode 100644
index 00000000..5a7653fe
--- /dev/null
+++ b/cbox_diff/cbox-diff/cbox-diff-2.luisa
@@ -0,0 +1,166 @@
+// mat_cbox
+Surface cbox-white : Matte {
+  Kd : Constant {
+    //v { 0.725, 0.71, 0.68 }
+    v { 0.1, 0.1, 0.1 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-white-1 : Matte {
+  Kd : Constant {
+    v { 0.2, 0.8, 0.2 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-white-2 : Matte {
+  Kd : Constant {
+    v { 0.3, 0.3, 0.9 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-white-3 : Matte {
+  Kd : Constant {
+    v { 0.4, 0.4, 0.4 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-white-4 : Matte {
+  Kd : Constant {
+    v { 0.5, 0.3, 0.3 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-green : Matte {
+  Kd : Constant {
+    //v { 0.14, 0.45, 0.091 }
+    v { 0.8, 0.5, 0.1 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+Surface cbox-red : Matte {
+  Kd : Constant {
+    //v { 0.63, 0.065, 0.05 }
+    v { 0.9, 0.9, 0.9 }
+    requires_grad { true }
+    range { 0.00001, 0.99999 }
+  }
+}
+
+// shape_cbox
+Shape cbox-ceiling : Mesh {
+  file { "../../meshes/cbox-parts/ceiling.obj" }
+  surface { @cbox-white }
+}
+
+Shape cbox-floor : Mesh {
+  file { "../../meshes/cbox-parts/floor.obj" }
+  surface { @cbox-white-1 }
+}
+
+Shape cbox-left-wall : Mesh {
+  file { "../../meshes/cbox-parts/left-wall.obj" }
+  surface { @cbox-red }
+}
+
+Shape cbox-right-wall : Mesh {
+  file { "../../meshes/cbox-parts/right-wall.obj" }
+  surface { @cbox-green }
+}
+
+Shape cbox-back-wall : Mesh {
+  file { "../../meshes/cbox-parts/back-wall.obj" }
+  surface { @cbox-white-2 }
+}
+
+
+Shape cbox-light : Mesh {
+  file { "../../meshes/cbox-parts/light.obj" }
+  light : Diffuse {
+    emission : Constant {
+      //v { 10, 10, 10 }
+      v { 45.0, 45.0, 45.0 }
+    }
+  }
+}
+
+Shape cbox-tall-box : Mesh {
+  file { "../../meshes/cbox-parts/tall-box.obj" }
+  surface { @cbox-white-3 }
+}
+
+Shape cbox-short-box : Mesh {
+  file { "../../meshes/cbox-parts/short-box.obj" }
+  surface { @cbox-white-4 }
+}
+
+
+Shape cbox : Group {
+  shapes {
+    @cbox-left-wall,
+    @cbox-ceiling,
+    @cbox-floor,
+    @cbox-right-wall,
+    @cbox-back-wall,
+    @cbox-tall-box,
+    @cbox-short-box,
+    @cbox-light
+  }
+}
+
+Film film : Color {
+  resolution { 1024 }
+  exposure { 0 }
+}
+
+Camera camera : Pinhole {
+  position { 0.0, 1.0, 5.0 }
+  fov { 27.8 }
+  spp { 1024 }
+  film { @film }
+  file { "../../renders/cbox-diff.exr" }
+  filter : Gaussian {
+    radius { 1 }
+  }
+  target : Image {
+    file { "../../renders/cbox-ref.exr" }
+  }
+}
+
+//Integrator pt : MegaRadiativeDiff {
+Integrator pt : MegaReplayDiff {
+  sampler : Independent {}
+  depth { 10 }
+  rr_depth { 5 }
+
+  display_camera_index { 0 }
+  save_process { true }
+  loss : L2 {}
+  iterations { 100 }
+
+  optimizer : Adam {
+    learning_rate { 0.003 }
+  }
+}
+
+render {
+  spectrum : sRGB {}
+  cameras {
+    @camera
+  }
+  shapes {
+    @cbox
+  }
+  integrator { @pt }
+}
diff --git a/cbox_diff/cbox-diff/cbox-ref-2.luisa b/cbox_diff/cbox-diff/cbox-ref-2.luisa
new file mode 100644
index 00000000..aefab0ca
--- /dev/null
+++ b/cbox_diff/cbox-diff/cbox-ref-2.luisa
@@ -0,0 +1,111 @@
+// mat_cbox
+Surface cbox-white : Matte {
+  Kd : Constant {
+    v { 0.725, 0.71, 0.68 }
+  }
+}
+
+Surface cbox-green : Matte {
+  Kd : Constant {
+    v { 0.14, 0.45, 0.091 }
+  }
+}
+
+Surface cbox-red : Matte {
+  Kd : Constant {
+    v { 0.63, 0.065, 0.05 }
+  }
+}
+
+// shape_cbox
+Shape cbox-ceiling : Mesh {
+  file { "../../meshes/cbox-parts/ceiling.obj" }
+  surface { @cbox-white }
+}
+
+Shape cbox-floor : Mesh {
+  file { "../../meshes/cbox-parts/floor.obj" }
+  surface { @cbox-white }
+}
+
+Shape cbox-left-wall : Mesh {
+  file { "../../meshes/cbox-parts/left-wall.obj" }
+  surface { @cbox-red }
+}
+
+Shape cbox-right-wall : Mesh {
+  file { "../../meshes/cbox-parts/right-wall.obj" }
+  surface { @cbox-green }
+}
+
+Shape cbox-back-wall : Mesh {
+  file { "../../meshes/cbox-parts/back-wall.obj" }
+  surface { @cbox-white }
+}
+
+
+Shape cbox-light : Mesh {
+  file { "../../meshes/cbox-parts/light.obj" }
+  light : Diffuse {
+    emission : Constant {
+      v { 45.0, 45.0, 45.0 }
+    }
+  }
+}
+
+Shape cbox-tall-box : Mesh {
+  file { "../../meshes/cbox-parts/tall-box.obj" }
+  surface { @cbox-white }
+}
+
+Shape cbox-short-box : Mesh {
+  file { "../../meshes/cbox-parts/short-box.obj" }
+  surface { @cbox-white }
+}
+
+
+Shape cbox : Group {
+  shapes {
+    @cbox-floor,
+    @cbox-ceiling,
+    @cbox-left-wall,
+    @cbox-right-wall,
+    @cbox-back-wall,
+    @cbox-tall-box,
+    @cbox-short-box,
+    @cbox-light
+  }
+}
+
+Film film : Color {
+  resolution { 1024 }
+  exposure { 0 }
+}
+
+Camera camera : Pinhole {
+  position { 0.0, 1.0, 5.0 }
+  fov { 27.8 }
+  spp { 1024 }
+  film { @film }
+  file { "../../renders/cbox-ref.exr" }
+  filter : Gaussian {
+    radius { 1 }
+  }
+}
+
+Integrator pt : MegaPath {
+  sampler : Independent {}
+  depth { 10 }
+  rr_depth { 5 }
+}
+
+render {
+  spectrum : sRGB {}
+  cameras {
+    @camera
+  }
+  shapes {
+    @cbox
+  }
+  integrator { @pt }
+}
diff --git a/cbox_diff/meshes/cbox-parts/back-wall.obj b/cbox_diff/meshes/cbox-parts/back-wall.obj
new file mode 100644
index 00000000..0bd18b23
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/back-wall.obj
@@ -0,0 +1,9 @@
+v  -1.00  0.00  -1.00
+v   1.00  0.00  -1.00
+v   1.00  2.00  -1.00
+v  -1.00  2.00  -1.00
+vt 0 1
+vt 1 1
+vt 1 0
+vt 0 0
+f -4/-4 -3/-3 -2/-2 -1/-1
diff --git a/cbox_diff/meshes/cbox-parts/ceiling.obj b/cbox_diff/meshes/cbox-parts/ceiling.obj
new file mode 100644
index 00000000..8da3b1ac
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/ceiling.obj
@@ -0,0 +1,5 @@
+v  -1.00  2.00   1.00
+v  -1.00  2.00  -1.00
+v   1.00  2.00  -1.00
+v   1.00  2.00   1.00
+f -4 -3 -2 -1
\ No newline at end of file
diff --git a/cbox_diff/meshes/cbox-parts/floor.obj b/cbox_diff/meshes/cbox-parts/floor.obj
new file mode 100644
index 00000000..4ab9b6ee
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/floor.obj
@@ -0,0 +1,5 @@
+v  -1.00  0.00   1.00
+v   1.00  0.00   1.00
+v   1.00  0.00  -1.00
+v  -1.00  0.00  -1.00
+f -4 -3 -2 -1
diff --git a/cbox_diff/meshes/cbox-parts/left-wall.obj b/cbox_diff/meshes/cbox-parts/left-wall.obj
new file mode 100644
index 00000000..834a6120
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/left-wall.obj
@@ -0,0 +1,5 @@
+v  -1.00  0.00   1.00
+v  -1.00  0.00  -1.00
+v  -1.00  2.00  -1.00
+v  -1.00  2.00   1.00
+f -4 -3 -2 -1
diff --git a/cbox_diff/meshes/cbox-parts/light.obj b/cbox_diff/meshes/cbox-parts/light.obj
new file mode 100644
index 00000000..2f817835
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/light.obj
@@ -0,0 +1,5 @@
+v	-0.24  1.98   0.16
+v	-0.24  1.98  -0.22
+v	 0.23  1.98  -0.22
+v	 0.23  1.98   0.16
+f -4 -3 -2 -1
diff --git a/cbox_diff/meshes/cbox-parts/right-wall.obj b/cbox_diff/meshes/cbox-parts/right-wall.obj
new file mode 100644
index 00000000..f415a00d
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/right-wall.obj
@@ -0,0 +1,5 @@
+v	1.00  0.00  -1.00
+v	1.00  0.00   1.00
+v	1.00  2.00   1.00
+v	1.00  2.00  -1.00
+f -4 -3 -2 -1
diff --git a/cbox_diff/meshes/cbox-parts/short-box.obj b/cbox_diff/meshes/cbox-parts/short-box.obj
new file mode 100644
index 00000000..742a8e65
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/short-box.obj
@@ -0,0 +1,41 @@
+# Top Face
+v	0.53  0.60   0.75
+v	0.70  0.60   0.17
+v	0.13  0.60   0.00
+v  -0.05  0.60   0.57
+f -4 -3 -2 -1
+
+# Left Face
+v  -0.05  0.00   0.57
+v  -0.05  0.60   0.57
+v   0.13  0.60   0.00
+v   0.13  0.00   0.00
+f -4 -3 -2 -1
+
+# Front Face
+v	0.53  0.00   0.75
+v	0.53  0.60   0.75
+v  -0.05  0.60   0.57
+v  -0.05  0.00   0.57
+f -4 -3 -2 -1
+
+# Right Face
+v	0.70  0.00   0.17
+v	0.70  0.60   0.17
+v	0.53  0.60   0.75
+v	0.53  0.00   0.75
+f -4 -3 -2 -1
+
+# Back Face
+v	0.13  0.00   0.00
+v	0.13  0.60   0.00
+v	0.70  0.60   0.17
+v	0.70  0.00   0.17
+f -4 -3 -2 -1
+
+# Bottom Face
+v	0.53  0.00   0.75
+v	0.70  0.00   0.17
+v	0.13  0.00   0.00
+v  -0.05  0.00   0.57
+f -12 -11 -10 -9
diff --git a/cbox_diff/meshes/cbox-parts/tall-box.obj b/cbox_diff/meshes/cbox-parts/tall-box.obj
new file mode 100644
index 00000000..1fc35a86
--- /dev/null
+++ b/cbox_diff/meshes/cbox-parts/tall-box.obj
@@ -0,0 +1,41 @@
+# Top Face
+v	-0.53  1.20   0.09
+v	 0.04  1.20  -0.09
+v	-0.14  1.20  -0.67
+v	-0.71  1.20  -0.49
+f -4 -3 -2 -1
+
+# Left Face
+v	-0.53  0.00   0.09
+v	-0.53  1.20   0.09
+v	-0.71  1.20  -0.49
+v	-0.71  0.00  -0.49
+f -4 -3 -2 -1
+
+# Back Face
+v	-0.71  0.00  -0.49
+v	-0.71  1.20  -0.49
+v	-0.14  1.20  -0.67
+v	-0.14  0.00  -0.67
+f -4 -3 -2 -1
+
+# Right Face
+v	-0.14  0.00  -0.67
+v	-0.14  1.20  -0.67
+v	 0.04  1.20  -0.09
+v	 0.04  0.00  -0.09
+f -4 -3 -2 -1
+
+# Front Face
+v	 0.04  0.00  -0.09
+v	 0.04  1.20  -0.09
+v	-0.53  1.20   0.09
+v	-0.53  0.00   0.09
+f -4 -3 -2 -1
+
+# Bottom Face
+v	-0.53  0.00   0.09
+v	 0.04  0.00  -0.09
+v	-0.14  0.00  -0.67
+v	-0.71  0.00  -0.49
+f -8 -7 -6 -5
diff --git a/cbox_diff/renders/cbox-diff.exr b/cbox_diff/renders/cbox-diff.exr
new file mode 100644
index 00000000..a410c4c1
Binary files /dev/null and b/cbox_diff/renders/cbox-diff.exr differ
diff --git a/cbox_diff/renders/cbox-ref.exr b/cbox_diff/renders/cbox-ref.exr
new file mode 100644
index 00000000..0307289c
Binary files /dev/null and b/cbox_diff/renders/cbox-ref.exr differ