Changed endpoint to take a 3d uniform random number instead of 2d for volume sampling. Modified every dependency accordingly and added a flag to signal when the third sample is used. Updated all tests to correctly account for the use of Point3f over Point2f.

Author: Microno95

include/mitsuba/python/docstr.h

@@ -2508,6 +2508,10 @@ static const char *__doc_mitsuba_Endpoint_needs_sample_2 =
 R"doc(Does the method sample_ray() require a uniformly distributed 2D sample
 for the ``sample2`` parameter?)doc";
 
+static const char *__doc_mitsuba_Endpoint_needs_sample_2_3d =
+R"doc(Does the method sample_ray() require a uniformly distributed 3D sample
+for the ``sample2`` parameter?)doc";
+
 static const char *__doc_mitsuba_Endpoint_needs_sample_3 =
 R"doc(Does the method sample_ray() require a uniformly distributed 2D sample
 for the ``sample3`` parameter?)doc";

include/mitsuba/render/endpoint.h

@@ -135,10 +135,11 @@ class MI_EXPORT_LIB Endpoint : public Object {
      *     dimension of the emission profile.
      *
      * \param sample2
-     *    A uniformly distributed sample on the domain <tt>[0,1]^2</tt>. For
-     *    sensor endpoints, this argument corresponds to the sample position in
-     *    fractional pixel coordinates relative to the crop window of the
-     *    underlying film.
+     *    A uniformly distributed sample on the domain <tt>[0,1]^2</tt> (or
+     *    <tt>[0,1]^3</tt> if needs_sample_2_3d() == true). For sensor
+     *    endpoints, this argument corresponds to the sample position in
+     *    fractional pixel coordinates relative to the crop window of
+     *    the underlying film.
      *    This argument is ignored if <tt>needs_sample_2() == false</tt>.
      *
      * \param sample3
@@ -153,7 +154,7 @@ class MI_EXPORT_LIB Endpoint : public Object {
      *    and the actual used sampling density function.
      */
     virtual std::pair<Ray3f, Spectrum>
-    sample_ray(Float time, Float sample1, const Point2f &sample2,
+    sample_ray(Float time, Float sample1, const Point3f &sample2,
                const Point2f &sample3, Mask active = true) const;
 
     //! @}
@@ -186,15 +187,16 @@ class MI_EXPORT_LIB Endpoint : public Object {
      *    A reference position somewhere within the scene.
      *
      * \param sample
-     *     A uniformly distributed 2D point on the domain <tt>[0,1]^2</tt>.
+     *     A uniformly distributed 2D point on the domain <tt>[0,1]^2</tt> (
+     *     or <tt>[0,1]^3</tt> if <tt>needs_sample_2_3d() == true)</tt>.
      *
      * \return
      *     A \ref DirectionSample instance describing the generated sample
      *     along with a spectral importance weight.
      */
     virtual std::pair<DirectionSample3f, Spectrum>
     sample_direction(const Interaction3f &ref,
-                     const Point2f &sample,
+                     const Point3f &sample,
                      Mask active = true) const;
 
     /**
@@ -273,7 +275,7 @@ class MI_EXPORT_LIB Endpoint : public Object {
      *     along with an importance weight.
      */
     virtual std::pair<PositionSample3f, Float>
-    sample_position(Float time, const Point2f &sample,
+    sample_position(Float time, const Point3f &sample,
                     Mask active = true) const;
 
     /**
@@ -325,6 +327,12 @@ class MI_EXPORT_LIB Endpoint : public Object {
      */
     bool needs_sample_2() const { return m_needs_sample_2; }
 
+    /**
+     * \brief Does the method \ref sample_ray() require a uniformly distributed
+     * 2D or 3D sample for the \c sample2 parameter?
+     */
+    bool needs_sample_2_3d() const { return m_needs_sample_2_3d; }
+
     /**
      * \brief Does the method \ref sample_ray() require a uniformly distributed
      * 2D sample for the \c sample3 parameter?
@@ -398,6 +406,7 @@ class MI_EXPORT_LIB Endpoint : public Object {
     ref<Medium> m_medium;
     Shape *m_shape = nullptr;
     bool m_needs_sample_2 = true;
+    bool m_needs_sample_2_3d = false;
     bool m_needs_sample_3 = true;
     std::string m_id;
 };

include/mitsuba/render/scene.h

@@ -333,7 +333,7 @@ class MI_EXPORT_LIB Scene : public Object {
      *    </ul>
      */
     std::tuple<Ray3f, Spectrum, const EmitterPtr>
-    sample_emitter_ray(Float time, Float sample1, const Point2f &sample2,
+    sample_emitter_ray(Float time, Float sample1, const Point3f &sample2,
                        const Point2f &sample3, Mask active = true) const;
 
     /**
@@ -377,7 +377,7 @@ class MI_EXPORT_LIB Scene : public Object {
      */
     std::pair<DirectionSample3f, Spectrum>
     sample_emitter_direction(const Interaction3f &ref,
-                             const Point2f &sample,
+                             const Point3f &sample,
                              bool test_visibility = true,
                              Mask active = true) const;
 

include/mitsuba/render/sensor.h

@@ -61,7 +61,7 @@ class MI_EXPORT_LIB Sensor : public Endpoint<Float, Spectrum> {
      */
     virtual std::pair<RayDifferential3f, Spectrum>
     sample_ray_differential(Float time, Float sample1,
-                            const Point2f &sample2, const Point2f &sample3,
+                            const Point3f &sample2, const Point2f &sample3,
                             Mask active = true) const;
 
     /**

src/bsdfs/tests/test_polarizer.py

@@ -209,7 +209,7 @@ def spectrum_from_stokes(v):
         sampler.seed(0)
 
         # Sample ray from sensor
-        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5], [0.5, 0.5])
+        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5, 0.0], [0.5, 0.5])
 
         # Call integrator
         value, _, _ = integrator.sample(scene, sampler, ray)
@@ -311,7 +311,7 @@ def spectrum_from_stokes(v):
         sampler.seed(0)
 
         # Sample ray from sensor
-        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5], [0.5, 0.5])
+        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5, 0.0], [0.5, 0.5])
 
         # Call integrator
         value, _, _ = integrator.sample(scene, sampler, ray)

src/bsdfs/tests/test_retarder.py

@@ -360,7 +360,7 @@ def spectrum_from_stokes(v):
         sampler.seed(0)
 
         # Sample ray from sensor
-        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5], [0.5, 0.5])
+        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5, 0.0], [0.5, 0.5])
 
         # Call integrator
         value, _, _ = integrator.sample(scene, sampler, ray)
@@ -476,7 +476,7 @@ def spectrum_from_stokes(v):
         sampler.seed(0)
 
         # Sample ray from sensor
-        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5], [0.5, 0.5])
+        ray, _ = sensor.sample_ray_differential(0.0, 0.5, [0.5, 0.5, 0.0], [0.5, 0.5])
 
         # Call integrator
         value, _, _ = integrator.sample(scene, sampler, ray)

src/emitters/area.cpp

@@ -58,7 +58,7 @@ emitter shape and specify an :monosp:`area` instance as its child:
 template <typename Float, typename Spectrum>
 class AreaLight final : public Emitter<Float, Spectrum> {
 public:
-    MI_IMPORT_BASE(Emitter, m_flags, m_shape, m_medium)
+    MI_IMPORT_BASE(Emitter, m_flags, m_shape, m_medium, m_needs_sample_2_3d)
     MI_IMPORT_TYPES(Scene, Shape, Texture)
 
     AreaLight(const Properties &props) : Base(props) {
@@ -68,6 +68,7 @@ class AreaLight final : public Emitter<Float, Spectrum> {
                   "shape.");
 
         m_radiance = props.texture_d65<Texture>("radiance", 1.f);
+        m_needs_sample_2_3d = false;
 
         m_flags = +EmitterFlags::Surface;
         if (m_radiance->is_spatially_varying())
@@ -90,7 +91,7 @@ class AreaLight final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<Ray3f, Spectrum> sample_ray(Float time, Float wavelength_sample,
-                                          const Point2f &sample2, const Point2f &sample3,
+                                          const Point3f &sample2, const Point2f &sample3,
                                           Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleRay, active);
 
@@ -115,7 +116,7 @@ class AreaLight final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<DirectionSample3f, Spectrum>
-    sample_direction(const Interaction3f &it, const Point2f &sample, Mask active) const override {
+    sample_direction(const Interaction3f &it, const Point3f &sample, Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleDirection, active);
         Assert(m_shape, "Can't sample from an area emitter without an associated Shape.");
         DirectionSample3f ds;
@@ -124,13 +125,13 @@ class AreaLight final : public Emitter<Float, Spectrum> {
         // One of two very different strategies is used depending on 'm_radiance'
         if (likely(!m_radiance->is_spatially_varying())) {
             // Texture is uniform, try to importance sample the shape wrt. solid angle at 'it'
-            ds = m_shape->sample_direction(it, sample, active);
+            ds = m_shape->sample_direction(it, Point2f(sample.x(), sample.y()), active);
             active &= dr::dot(ds.d, ds.n) < 0.f && dr::neq(ds.pdf, 0.f);
 
             si = SurfaceInteraction3f(ds, it.wavelengths);
         } else {
             // Importance sample the texture, then map onto the shape
-            auto [uv, pdf] = m_radiance->sample_position(sample, active);
+            auto [uv, pdf] = m_radiance->sample_position(Point2f(sample.x(), sample.y()), active);
             active &= dr::neq(pdf, 0.f);
 
             si = m_shape->eval_parameterization(uv, +RayFlags::All, active);
@@ -193,7 +194,7 @@ class AreaLight final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<PositionSample3f, Float>
-    sample_position(Float time, const Point2f &sample,
+    sample_position(Float time, const Point3f &sample,
                     Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSamplePosition, active);
         Assert(m_shape, "Cannot sample from an area emitter without an associated Shape.");
@@ -202,10 +203,10 @@ class AreaLight final : public Emitter<Float, Spectrum> {
         PositionSample3f ps;
         if (!m_radiance->is_spatially_varying()) {
             // Radiance not spatially varying, use area-based sampling of shape
-            ps = m_shape->sample_position(time, sample, active);
+            ps = m_shape->sample_position(time, Point2f(sample.x(), sample.y()), active);
         } else {
             // Importance sample texture
-            auto [uv, pdf] = m_radiance->sample_position(sample, active);
+            auto [uv, pdf] = m_radiance->sample_position(Point2f(sample.x(), sample.y()), active);
             active &= dr::neq(pdf, 0.f);
 
             auto si = m_shape->eval_parameterization(uv, +RayFlags::All, active);

src/emitters/constant.cpp

@@ -91,12 +91,12 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<Ray3f, Spectrum> sample_ray(Float time, Float wavelength_sample,
-                                          const Point2f &sample2, const Point2f &sample3,
+                                          const Point3f &sample2, const Point2f &sample3,
                                           Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleRay, active);
 
         // 1. Sample spatial component
-        Vector3f v0 = warp::square_to_uniform_sphere(sample2);
+        Vector3f v0 = warp::square_to_uniform_sphere(Point2f(sample2.x(), sample2.y()));
         Point3f orig = dr::fmadd(v0, m_bsphere.radius, m_bsphere.center);
 
         // 2. Sample diral component
@@ -114,11 +114,11 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<DirectionSample3f, Spectrum> sample_direction(const Interaction3f &it,
-                                                            const Point2f &sample,
+                                                            const Point3f &sample,
                                                             Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleDirection, active);
 
-        Vector3f d = warp::square_to_uniform_sphere(sample);
+        Vector3f d = warp::square_to_uniform_sphere(Point2f(sample.x(), sample.y()));
 
         // Automatically enlarge the bounding sphere when it does not contain the reference point
         Float radius = dr::maximum(m_bsphere.radius, dr::norm(it.p - m_bsphere.center)),
@@ -127,7 +127,7 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
         DirectionSample3f ds;
         ds.p       = dr::fmadd(d, dist, it.p);
         ds.n       = -d;
-        ds.uv      = sample;
+        ds.uv      = Point2f(sample.x(), sample.y());
         ds.time    = it.time;
         ds.pdf     = warp::square_to_uniform_sphere_pdf(d);
         ds.delta   = false;
@@ -166,7 +166,7 @@ class ConstantBackgroundEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<PositionSample3f, Float>
-    sample_position(Float /*time*/, const Point2f & /*sample*/,
+    sample_position(Float /*time*/, const Point3f & /*sample*/,
                     Mask /*active*/) const override {
         if constexpr (dr::is_jit_v<Float>) {
             /* When virtual function calls are recorded in symbolic mode,

src/emitters/directional.cpp

@@ -114,13 +114,14 @@ MI_VARIANT class DirectionalEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<Ray3f, Spectrum> sample_ray(Float time, Float wavelength_sample,
-                                          const Point2f &spatial_sample,
+                                          const Point3f &spatial_sample,
                                           const Point2f & /*direction_sample*/,
                                           Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleRay, active);
 
+        auto spatial_sample_2d = Point2f(spatial_sample.x(), spatial_sample.y());
         // 1. Sample spatial component
-        Point2f offset =  warp::square_to_uniform_disk_concentric(spatial_sample);
+        Point2f offset =  warp::square_to_uniform_disk_concentric(spatial_sample_2d);
 
         // 2. "Sample" directional component (fixed, no actual sampling required)
         const auto trafo = m_to_world.value();
@@ -135,7 +136,7 @@ MI_VARIANT class DirectionalEmitter final : public Emitter<Float, Spectrum> {
         si.t    = 0.f;
         si.time = time;
         si.p    = origin;
-        si.uv   = spatial_sample;
+        si.uv   = spatial_sample_2d;
         auto [wavelengths, wav_weight] =
             sample_wavelengths(si, wavelength_sample, active);
 
@@ -147,7 +148,7 @@ MI_VARIANT class DirectionalEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<DirectionSample3f, Spectrum>
-    sample_direction(const Interaction3f &it, const Point2f & /*sample*/,
+    sample_direction(const Interaction3f &it, const Point3f & /*sample*/,
                      Mask active) const override {
         MI_MASKED_FUNCTION(ProfilerPhase::EndpointSampleDirection, active);
 
@@ -199,7 +200,7 @@ MI_VARIANT class DirectionalEmitter final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<PositionSample3f, Float>
-    sample_position(Float /*time*/, const Point2f & /*sample*/,
+    sample_position(Float /*time*/, const Point3f & /*sample*/,
                     Mask /*active*/) const override {
         if constexpr (dr::is_jit_v<Float>) {
             // When vcalls are recorded in symbolic mode, we can't throw an exception,

src/emitters/directionalarea.cpp

@@ -86,11 +86,11 @@ class DirectionalArea final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<Ray3f, Spectrum> sample_ray(Float time, Float wavelength_sample,
-                                          const Point2f &sample2,
+                                          const Point3f &sample2,
                                           const Point2f & /*sample3*/,
                                           Mask active) const override {
         // 1. Sample spatial component
-        PositionSample3f ps = m_shape->sample_position(time, sample2);
+        auto [ps, ps_weight] = sample_position(time, sample2, active);
 
         // 2. Directional component is the normal vector at that position.
         const Vector3f d = ps.n;
@@ -115,7 +115,7 @@ class DirectionalArea final : public Emitter<Float, Spectrum> {
      *       flat surface.
      */
     std::pair<DirectionSample3f, Spectrum>
-    sample_direction(const Interaction3f & /*it*/, const Point2f & /*sample*/,
+    sample_direction(const Interaction3f & /*it*/, const Point3f & /*sample*/,
                      Mask /*active*/) const override {
         return { dr::zeros<DirectionSample3f>(), dr::zeros<Spectrum>() };
     }
@@ -127,10 +127,10 @@ class DirectionalArea final : public Emitter<Float, Spectrum> {
     }
 
     std::pair<PositionSample3f, Float>
-    sample_position(Float time, const Point2f &sample,
+    sample_position(Float time, const Point3f &sample,
                     Mask active) const override {
         Assert(m_shape, "Can't sample from an area emitter without an associated Shape.");
-        PositionSample3f ps = m_shape->sample_position(time, sample, active);
+        PositionSample3f ps = m_shape->sample_position(time, Point2f(sample.x(), sample.y()), active);
         Float weight        = dr::select(ps.pdf > 0.f, dr::rcp(ps.pdf), 0.f);
         return { ps, weight };
     }