Bookshelf

The Bookshelf scene is very difficult to render with unidirectional path tracing due to complex glossy interreflections and light sources encased by glass. Radiance-based path guiding is highly effective at rendering this scene, with the GMMs by Vorba et al. [2014] performing the best among all approaches. Primary-sample-space path-sampling techniques offer little to no benefit over unidirectional path tracing with our NPS slightly outperforming PSSPS [Guo et al. 2018] with an equal number of samples.
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Charts

Lower values are better (for SSIM, we plot 1-SSIM).
MAPE
SMAPE
L1
MRSE
L2
1-SSIM

Metrics

MetricPath TracingPPGGMMPSSPSNPS KLNPG-Radiance KLNPG-Product KL scalarNPG-Product KLNPG-Product χ²
Mega Samples236236236236236236236236236
Render Time74s2.5m17m78s3.5m8.1m10m10m12m
MAPE0.7960.1250.09820.7550.6810.1140.2500.1200.168
SMAPE0.9200.1480.1160.8230.7710.1340.2680.1350.200
L10.1480.02110.01730.1230.09760.01740.04000.01630.0210
MRSE0.5900.01167.99e−30.5570.4220.01010.08110.01750.0201
L20.02696.19e−43.92e−40.01900.01365.15e−43.08e−36.60e−48.84e−4
1-SSIM0.8930.2360.1710.8550.8270.2090.4360.2150.333