The problem seems to be that Java3D expects Linear RGB as input color space:https://forum.jogamp.org/sRGB-and-gamma ... 38946.html

I've tested this by manually setting the RGB value of a wall to a gamma-corrected value ( lin=255*(val/255, 2.2) ), which makes yafaray and sunflow output the correct color.

There are two options: 1) feed in a generated texture or 2) convert the colors to linear RGB