LightFieldSphere
The LightFieldSphere recipe contains a sphere rendered under light field illumination. This means the illumination in the scene varies spatially based on an input image which acts like an "illumination texture".
This example was generously contributed by Gizem Küçükoğlu.
Above, Mitsuba rendered the scene.
The parent scene contains a sphere and an "environment map" light source which accepts spectral information from a "light probe" RGBE data file. The data file was generously made available by Bernhard Vogl.
The sphere uses a Ward model material. The sphere's specular reflectance varies across four conditions. So the effects of the light field illumination may be observed only subtly, or as a crisp, mirror-like reflection.
Use the script rtbMakeLightFieldSphere.m to produce the images above.
In the above example, the RGBE light probe data were promoted to spectral representation internally by the Mitsuba renderer. Mitsuba can also accept light probe data in the form of a multi-spectral OpenEXR file. This allows fine control of illumination both spatially and spectrally.
As of writing, we don't have any good multi-spectral light probe data. But we have plenty of multi-spectral rendering outputs. We used one of these as a proof of concept, that Mitsuba really accepts multi-spectral light probe inputs.
For this "spectral" variant of the LightFieldSphere scene, the input file for the light probe was the original multi-spectral output of the LightFieldSphere rendering. So this example is curiously self-referential.
The executive script rtbMakeLightFieldSphere.m produced the variant image below. We changed one line of the LightFieldSphereMappings.json mappings file to specify the multi-spectral light probe.
Above, Mitsuba rendered the scene.