Portal-Masked Environment Map Sampling
(Horse Room Image Comparison)

Below you can find interactive versions of the result comparisons for the Horse Room scene from Figure 4 and Table 1 of the paper "Portal-Masked Environment Map Sampling". We compare our new importance sampling technique to three baseline techniques: sampling only the environment map, sampling only the solid angle of the portal, or multiple importance sampling (MIS) of these two previous methods. All images (except for reference) use 8 samples per pixel, but the sampling techniques result in different variance and render times. To quantify the relative performance of each technique in a single representative number, we report the time-to-unit-variance (TTUV)—computed as the MSE × render time—in parentheses.

Tip: Move the mouse over the images to compare the algorithms on specific parts of the scene.
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Ambient environment map

Envmap Sampling<br />(TTUV: 52.87) Portal S.Angle Sampling<br />(TTUV: <strong>30.39</strong>) Envmap/S.Angle MIS<br />(TTUV: 39.13) Ours (portal visible energy selection)<br />(TTUV: 33.20)
Reference Envmap/S.Angle MIS<br />(TTUV: 39.13) Ours (solid angle selection)<br />(TTUV: 33.02) Ours (portal visible energy selection)<br />(TTUV: 33.20)

Factory environment map

Envmap Sampling<br />(TTUV: 135.40) Portal S.Angle Sampling<br />(TTUV: 293.52) Envmap/S.Angle MIS<br />(TTUV: 170.40) Ours (portal visible energy selection)<br />(TTUV: <strong>68.59</strong>)
Reference Envmap/S.Angle MIS<br />(TTUV: 170.40) Ours (solid angle selection)<br />(TTUV: 79.88) Ours (portal visible energy selection)<br />(TTUV: <strong>68.59</strong>)

Sunny environment map

Envmap Sampling<br />(TTUV: 20.40) Portal S.Angle Sampling<br />(TTUV: 5941.94) Envmap/S.Angle MIS<br />(TTUV: 30.72) Ours (portal visible energy selection)<br />(TTUV: <strong>15.39</strong>)
Reference Envmap/S.Angle MIS<br />(TTUV: 30.72) Ours (solid angle selection)<br />(TTUV: 42.15) Ours (portal visible energy selection)<br />(TTUV: <strong>15.39</strong>)