[Radiance-general] daylight factor and rtrace cmd

[Thomas Bleicher]

On Fri, Jul 17, 2009 at 3:45 AM, Greg Ward<gward at lmi.net> wrote:
> Yes, the -oo option combined with -I doesn't really work properly in rtrace,
> as it "fakes" an intersection with an ideal diffuse surface a tiny amount
> (about 1e-6) in front of the point you specified, while setting the ray
> origin arbitrarily one unit before it.  No actual intersection calculation
> is done, so no worries about intervening rays.

So the 1 unit offset is only a fake to make the output options happy
and does not interfere with the scene geometry. That's good.

> This is something I should
> fix, but since you give the origin on input, it hasn't come up very often
> where people want the same origin on output.

It's a bit inconsistent to throw a file at rtrace specifying what you want
and getting back from rtace what it actually did. Like ordering a door
and getting delivered some planks and a saw. (Should we call this
'IKEA rendering'?)

While we're at it, I think that this virtual intersection also swallows one
bounce out of your '-ab' specs. That only becomes obvious when you
try to eliminate indirect contributions ('-ab 0' and '-ab 1') but then it's
rather annoying when you don't remember it.

What's the community's opinion? Should rtrace raise the bounce count
for '-I' internally or should it just be well document? I'm not sure what's
more consistent with the way Radiance behaves now or if there are any
side effects.

Thomas