libpython: allow extracting the bitmap underlying an environment map

include/mitsuba/render/emitter.h

@@ -534,6 +534,24 @@ public:
 	 */
 	inline Float getSamplingWeight() const { return m_samplingWeight; }
 
+	/**
+	 * \brief Return a bitmap representation of the emitter
+	 *
+	 * Some types of light sources (projection lights, environment maps)
+	 * are closely tied to an underlying bitmap data structure. This function
+	 * can be used to return this information for various purposes.
+	 *
+	 * When the class implementing this interface is a bitmap-backed texture,
+	 * this function directly returns the underlying bitmap. When it is procedural,
+	 * a bitmap version must first be generated. In this case, the parameter
+	 * \ref sizeHint is used to control the target size. The default
+	 * value <tt>-1, -1</tt> allows the implementation to choose a suitable
+	 * size by itself.
+	 *
+	 * \remark The default implementation throws an exception
+	 */
+	virtual ref<Bitmap> getBitmap(const Vector2i &sizeHint = Vector2i(-1, -1)) const;
+
 	/// Serialize this emitter to a binary data stream
 	virtual void serialize(Stream *stream, InstanceManager *manager) const;
 

src/emitters/envmap.cpp

@@ -632,6 +632,10 @@ public:
 			* m_normalization / std::max(std::abs(sinTheta), Epsilon);
 	}
 
+	ref<Bitmap> getBitmap(const Vector2i &/* unused */) const {
+		return m_mipmap->toBitmap();
+	}
+
 	std::string toString() const {
 		std::ostringstream oss;
 		oss << "EnvironmentMap[" << endl

src/libpython/render.cpp

@@ -607,7 +607,10 @@ void export_render() {
 		.def("eval", &Emitter::eval, BP_RETURN_VALUE)
 		.def("getSamplingWeight", &Emitter::getSamplingWeight)
 		.def("isEnvironmentEmitter", &Emitter::isEnvironmentEmitter)
-		.def("evalEnvironment", &Emitter::evalEnvironment, BP_RETURN_VALUE);
+		.def("evalEnvironment", &Emitter::evalEnvironment, BP_RETURN_VALUE)
+		.def("isCompound", &Emitter::isCompound)
+		.def("getElement", &Emitter::getElement, BP_RETURN_VALUE)
+		.def("getBitmap", &Emitter::getBitmap, getBitmap_overloads()[BP_RETURN_VALUE]);
 
 	BP_SETSCOPE(Emitter_class);
 	bp::enum_<Emitter::EEmitterFlags>("EEmitterFlags")

src/librender/emitter.cpp

@@ -144,6 +144,10 @@ bool Emitter::isCompound() const {
 	return false;
 }
 
+ref<Bitmap> Emitter::getBitmap(const Vector2i &sizeHint) const {
+	NotImplementedError("getBitmap");
+}
+
 MTS_IMPLEMENT_CLASS(Emitter, false, AbstractEmitter)
 MTS_IMPLEMENT_CLASS(AbstractEmitter, true, ConfigurableObject)
 MTS_NAMESPACE_END