this is what the coder of EQUINOX-3D told me:
The GI system has many parts, so I here’s an approximate break-down:
- Interactive ray-tracer : 2-4 years
- Path-tracer (with arbitrary BRDFs, physically accurate metals, importance sampling, caustics, motion blur, depth-of field etc.) : about 3 years
- Photon mapping renderer (caustics, spectral rendering with dispersion, volumetric effects, multiple scattering, sub-surface scattering etc.) : about 5 years
- Light-map rendering support for all the above : about 3 months
- Spherical harmonics support (including pre-processing for per-vertex and texture-based SH) : about 6 months
All these are happening in parallel and I have a full-time job, so I can’t dedicate all my time to EQUINOX-3D. Otherwise it may have been faster.
Also, the whole system is still under constant development. I add new features as the field evolves and new techniques are invented.
I think this might shed some light on approximate time estimates for Blender Internal.