Filippo Veniero explains how use the Mitsuba render engine to obtain a physically accurate glass render in Blender, complete with water, bubbles and a straw.

In this tutorial I'll show you how to use Mitsuba in Blender to create a physically correct glass cup. Mitsuba is an open source, physically-based renderer, runs on Linux, Mac OS X, Windows and is extremely modular. Many rendering techniques are available (direct illumination, path tracer, bidirectional path trace, photon map and so on). It supports volume rendering and the most commonly used scattering models (rough glass, plastic, metal).

Download the Mitsuba software and the plug-in for Blender. Now install Mitsuba, unzip the plug-in and copy the folder called Mitsuba into Blender/2.69/scripts/addons.

Modeling the glass

Open Blender and enable Mitsuba (File > User Preferences > Addons). Change the render engine from Blender to Mitsuba and write the path of the executable file in the Executable Path field.

Delete the default cube and add a circle of 16 vertices. Enter Edit mode and extrude along the Z axis and scale just a little. Close the bottom of the glass and model the inside, then add Subdivision Surface modifier (level 2) and set the Shading to smooth. Call this mesh 'Glass'.

Create the water

In Edit mode, select the vertices inside the glass and separate them ( P > by selection ). Call this part 'water'. Now select the vertices of the first edge loop, duplicate and separate them: call this new mesh 'water_top'. Close them by extruding and scaling and don't forget the meniscus (the curve in the upper surface of the liquid against the side of the glass). Check the mesh's Normals ? it's very important that they are consistent and face the same direction!

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