Radiance resolution and filtering test


To 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.oct
Of additional importance is the use of rpict's default values for the following parameters:

-pj 0.67 -ps 4 -pt 0.05
The 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:


Radiance 3.4, PIII 500 MHz

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

Radiance 3.5, Athlon XP 2 GHz

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.


Mark J. Stock, Aerospace Engineering, The University of Michigan

page created: 2002-08-11

last modified: 2003-08-19