|An enlarged PNG version of the 8x4 pixel OpenEXR environment map.|
Here are the final results of my tests, after I made all of the improvements and fixes:
|No smoothing. BRDF-based distribution path tracing.|
|No smoothing. Direct illumination using environment map importance sampling.|
|Linear interpolation. BRDF-based distribution path tracing.|
|Linear interpolation. Direct illumination using environment map importance sampling.|
You might notice some subtle colored strips on the edges of these images. That's due to anti-aliasing and jittering (of the output image, not the environment map) which, when combined with the equirectangular mapping, cause some samples to end up on the other edges.