Differentiable Mipmap

include/mitsuba/core/ray.h

@@ -106,8 +106,8 @@ struct RayDifferential : Ray<Point_, Spectrum_> {
     void scale_differential(Float amount) {
         o_x = dr::fmadd(o_x - o, amount, o);
         o_y = dr::fmadd(o_y - o, amount, o);
-        d_x = dr::fmadd(d_x - d, amount, d);
-        d_y = dr::fmadd(d_y - d, amount, d);
+        d_x = dr::normalize(dr::fmadd(d_x - d, amount, d));
+        d_y = dr::normalize(dr::fmadd(d_y - d, amount, d));
     }
 
     DRJIT_STRUCT(RayDifferential, o, d, maxt, time,

include/mitsuba/render/bsdf.h

@@ -572,12 +572,13 @@ typename SurfaceInteraction<Float, Spectrum>::BSDFPtr SurfaceInteraction<Float,
 
     /// TODO: revisit the 'false' default for autodiff mode once there are actually BRDFs using
     /// differentials
-    if constexpr (!dr::is_diff_v<Float>) {
-        if (!has_uv_partials() && dr::any(bsdf->needs_differentials()))
+    // if constexpr (!dr::is_diff_v<Float>) {
+        if (dr::any_or<true>(bsdf->needs_differentials())){
             compute_uv_partials(ray);
-    } else {
-        DRJIT_MARK_USED(ray);
-    }
+        }
+    // } else {
+    //     DRJIT_MARK_USED(ray);
+    // }
 
     return bsdf;
 }

notebook/figures/meshes/Plane-v4.pbrt

@@ -0,0 +1,13 @@
+# Converted from "Plane.obj" by obj2pbrt
+# Scene bounds: (-25.000000, 0.000000, -52.500000) - (25.000000, 0.000000, 2.500000)
+# Name "Plane"
+
+AttributeBegin
+    # Material unspecified in OBJ file
+    Shape "trianglemesh"
+        "point2 uv" [ 0 0 1 1 0 1 1 0 
+            ]
+        "integer indices" [ 0 1 2 0 3 1 ]
+        "normal N" [ 0 1 0 0 1 0 0 1 0 0 1 0 ]
+        "point3 P" [ 25 0 2.5 -25 0 -52.5 -25 0 2.5 25 0 -52.5 ]
+AttributeEnd

notebook/figures/meshes/Plane.obj

@@ -0,0 +1,15 @@
+# Blender v3.5.0 Alpha OBJ File: 'plane.blend'
+# www.blender.org
+o Plane
+v -25.000000 0.000000 2.500000
+v 25.000000 0.000000 2.500000
+v -25.000000 0.000000 -52.500000
+v 25.000000 0.000000 -52.500000
+vt 1.000000 0.000000
+vt 0.000000 1.000000
+vt 0.000000 0.000000
+vt 1.000000 1.000000
+vn 0.0000 1.0000 0.0000
+s off
+f 2/1/1 3/2/1 1/3/1
+f 2/1/1 4/4/1 3/2/1

notebook/figures/meshes/Plane.pbrt

@@ -0,0 +1,34 @@
+# Converted from "Plane.obj" by obj2pbrt
+# Scene bounds: (-25.000000, 0.000000, -52.500000) - (25.000000, 0.000000, 2.500000)
+
+
+# Name "Plane"
+AttributeBegin
+# Material unspecified in OBJ file
+Shape "trianglemesh"
+  "point3 P" [ 
+	25 0 2.5
+	-25 0 -52.5
+	-25 0 2.5
+	25 0 -52.5
+]
+  "normal N" [ 
+	0 1 0
+	0 1 0
+	0 1 0
+	0 1 0
+]
+  "point2 st" [ 
+	0 0
+	1 1
+	0 1
+	1 0
+]
+  "integer indices" [ 
+	0 1 2
+	0 3 1
+	]
+
+AttributeEnd
+
+