POV-Ray : Newsgroups : povray.advanced-users : HDR Probes applied to select objects only? : Re: HDR Probes applied to select objects only? Server Time
26 Jul 2021 19:44:25 EDT (-0400)
  Re: HDR Probes applied to select objects only?  
From: PM 2Ring
Date: 28 Apr 2006 14:50:00
Message: <web.445262a44a78764e76ba2c900@news.povray.org>
"Tim McMurdo" <jod### [at] wohrrcom> wrote:
> "PM 2Ring" <nomail@nomail> wrote:
> > POV, or MegaPOV? And why? :)
> MegaPov...and the second is a very good question.

As I mentioned, I don't know MegaPov or how it implements HDRI, so my help
will be limited.

> I am creating an pretty sparse image of some objects sitting on a white
> plane. I want the reflections that an HDR image gives to the objects, but I
> only want the shadows of the objects on the plane.
> Using HDR applies colors to the white plane that I don't want.

Is it only the colours that are a problem? I still think you will have to do
this in multiple passes, but in the first pass, just use a greyscale
lightprobe to get a colour-free white plane.

> Perhaps a better way would be to use a texture on the plane that would not
> be affected by the HDR? Any hints?

I've been wracking my tired brain for how to do it in regular Pov. In the
method I've been using, I guess I'd use lightgroups on some or all of the
lightdome light sources, and I suppose I'd use a big gray_threshold to kill
the colours caused by radiosity, since that won't affect the coloured
reflections you want on your main objects.

This problem reminds of those 'portal' type pics that Rune did a while back.
Maybe he has some hints, or maybe Christoff or Warp can illuminate us.

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