Radiance resolution and filtering test Radiance resolution and filtering testTo test the output quality of Radiance's renderer rpict, a simple scene was rendered at a variety of resolutions, and filtered down using pfilt's various filters.
The rpict statement used is the following:
rpict -vp 10 -1 1 -vd -10 1 -1 -ab 2 -ar 128 -ad 512 -as 256 -af sphere.amb -t 60 -x 256 -y 256 sphere.octOf additional importance is the use of rpict's default values for the following parameters:
-pj 0.67 -ps 4 -pt 0.05The ambient file was populated from a render at 8 times final resolution, and was modified only slightly during the generation of the pre-filtered images. The -x and -y resolutions were increased in whole number multiples.
The perl script used to make the images in this table is called renderall.pl, and the source files are here: sphere.rad, checker.cal.
NOTE: the previous series of images (and performance times) were made using Radiance version 3.4 on a Pentium III 500 MHz machine. The -r option of pfilt was changed between versions 3.4 and 3.5. Thus, the second set of images and numbers were created using release 3.5 on an Athlon 2 GHz box.
The results of the test are as follows:
| Final resolution: 256x256 | Default (box) filter | Gaussian filter, 0.5 pixel radius | 0.75 pixel radius | 1.0 pixel radius | 1.25 pixel radius | 1.5 pixel radius |
| 1x final resolution render time: 1.18s |
 filter time: 0.08s |
 0.24s |
 0.62s |
 0.54s |
 0.62s |
 1.14s |
| 2x final resolution render time: 3.22s |
 filter time: 0.13s |
 0.55s |
 1.22s |
 1.57s |
 1.92s |
 2.80s |
| 3x final resolution render time: 5.95s |
 filter time: 0.23s |
 1.09s |
 1.89s |
 2.35s |
 3.89s |
 5.00s |
| 4x final resolution render time: 9.39s |
 filter time: 0.34s |
 1.75s |
 2.88s |
 4.30s |
 6.55s |
 9.84s |
| 5x final resolution render time: 12.05s |
 filter time: 0.53s |
 1.77s |
 4.17s |
 5.47s |
 9.98s |
 13.92s |
| - | Default (box) filter | Gaussian filter, 0.5 pixel radius | 0.75 pixel radius | 1.0 pixel radius | 1.25 pixel radius | 1.5 pixel radius |
| Final resolution: 256x256 | Default (box) filter | Gaussian filter, 0.5 pixel radius | 0.75 pixel radius | 1.0 pixel radius | 1.25 pixel radius | 1.5 pixel radius |
| 1x final resolution render time: 0.303s |
 filter time: 0.020s |
 0.111s |
 0.123s |
 0.195s |
 0.217s |
 0.338s |
| 2x final resolution render time: 0.799s |
 filter time: 0.037s |
 0.207s |
 0.350s |
 0.445s |
 0.684s |
 0.891s |
| 3x final resolution render time: 1.504s |
 filter time: 0.063s |
 0.332s |
 0.521s |
 0.809s |
 1.146s |
 1.713s |
| 4x final resolution render time: 2.293s |
 filter time: 0.096s |
 0.488s |
 0.932s |
 1.297s |
 2.107s |
 2.885s |
| 5x final resolution render time: 3.213s |
 filter time: 0.137s |
 0.516s |
 1.203s |
 1.629s |
 2.982s |
 3.861s |
| - | Default (box) filter | Gaussian filter, 0.5 pixel radius | 0.75 pixel radius | 1.0 pixel radius | 1.25 pixel radius | 1.5 pixel radius |
Of obvious importance is the need to render images at double or greater the final desired resolution. It seems that to maintain ideal edge detail, at least 4x final image resolution is needed. Additionally, it seems that at these higher resolutions, pfilt's default box filter performs just as well as the Gaussian filter with small radius.