On Thu, 04 Feb 1999 23:14:48 -0600, "Thorsten Froehlich"
<fro### [at] charliecnsiitedu> wrote:

>For the mosaic preview part that might be possible (and help to do the
>general prediction). Any other prediction of the render time based on the
>lines rendered so far (the only "easy" way I can think of) is not very
>useful for most scenes. For example you might have just a sky in the upper
>half of the image which renders fast, and the, in the lower part you might
>have a few hundret glass spheres, using a high max_trace_level and
>anti-aliasing the first line that intersect a few of the spheres might take
>a few times what the whole image took to the middle...

I know, that's why I am suggesting an estimate to be made based on
both speed reports. The mosaic preview will be the most accurate, but
then again, even a faked estimate is better than none at all, right?

>I usually use a very small preview image (like 32 * 24 for a 640 * 480
>image) with the _same_ options I will use for the final image and multiply
>the time it took for the small one to estimate the final render. Most of the
>time an additional factor of 1.05 to 1.1 is needed to account for background
>system tasks etc.

Antialiasing takes longer on smaller images if you account for
samples/pixel. AT least that's what my practice shows. I usually
render a 160x120 no AA, multiply the render time accordingly, multiply
it by [1+AA/3] and add it to the parsing time. Usually works pretty
fine, but why should *I* bother if the box can do it for me?

Come to think of it, can antialiasing be made *after* the image has
been traced? I.e., scan the pic and apply aa where needed. This has
several advantages over the current implementation:
1) instead of the up-and-left-only aa check all adjacent pixels will
be checked
2) one can see if aa is needed at all. Then one can do a pass with a
large threshold (0.5 for eg.) and lower it until the result is
satisfactory. If parse time is much lower than render time, this is a
pretty time-saving approach
3) dual processors or two computers can be easily made to work in
tandem with the field interlace option (two pov instances in the first
case), then one of them will only do the aa pass.

>    Thorsten

Regards,
Peter

Post a reply to this message