serious bugfix to the material exporter

data/blender/mitsuba/export/adjustments.py

@@ -35,7 +35,7 @@ class MtsAdjustments:
 		self.target_dir = target_dir
 		self.exported_materials = []
 		self.exported_textures = []
-		self.materials = materials if materials != None else bpy.data.textures
+		self.materials = materials if materials != None else bpy.data.materials
 		self.textures = textures if textures != None else bpy.data.textures
 
 	def exportWorldtrafo(self, trafo):
@@ -142,7 +142,8 @@ class MtsAdjustments:
 		if name in self.materials:
 			return self.materials[name]
 		else:
-			raise Exception('Failed to find material "%s"' % name)
+			raise Exception('Failed to find material "%s" in "%s"' % (name,
+				str(self.materials)))
 
 	def exportTexture(self, mat):
 		if mat.name in self.exported_textures:

doc/blender.tex

@@ -6,3 +6,8 @@ Blender application bundle (e.g. \code{blender.app/Contents/MacOS/}\textbf{<BLEN
 
 When specifying the Mitsuba executable path, note that you must again provide
 the path to the binary within the application bundle, e.g. \code{/Applications/Mitsuba.app/Contents/MacOS/mitsuba}
+
+\subsection{General information}
+- MtsBlend always uses the first material slot as the main material of an
+object. When building custom materials (e.g. mixtures using the compound BSDF),
+make sure that the first slot contains the final material you wish to assign.