Shadow transperancy problems 2004-04-09 - By Tony Owen
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Has anybody tried using a greyscale transparency map to get soft shadows
with raytracing?
-- -- Original Message -- --
From: "Thomas Moffat Grimes" <thomas@(protected)>
To: <truespace@(protected)>
Sent: Friday, April 09, 2004 8:36 AM
Subject: Re: [TSML] Shadow transperancy problems
> Hi John,
>
> I don't believe so, based on my current understanding of the technical
> details involved (which are not necessarily that great!). As far as I
know,
> the only way you can pick up the edge of an alpha mask is to cast rays
into
> the scene that can detect where that edge is, which means it can only be
> done with raytracing.
>
> So, as far as I know, the only way to achieve soft shadows with
transparency
> and / or alpha masks etc is to use raytracing (I think that's a
restriction
> that would likely crop up with other renderers too, not some thing unique
to
> tS), and to use the raytracing methods of getting soft shadows. BTW, that
> method is more accurate anyway, and generally gives better results, but it
> is slower due to being computationally expensive.
>
> HTH!
> Tom
>
> Thomas Moffat Grimes
> Marketing Communications
> Caligari Corporation
>
> mailto:thomas@(protected)
> http://www.caligari.com
>
> -- --Original Message-- --
> From: Visual Impact [mailto:visualimpact@(protected)]
> Sent: Tuesday, April 06, 2004 7:25 PM
> To: truespace@(protected)
> Subject: Re: [TSML] Shadow transperancy problems
>
>
> Thanks for your reply Tom. That news really sucks though. Any chance of
> shadow transperancy being available for shadow maps in the future.
> John
>
> Thomas Moffat Grimes wrote:
>
> >Hi John,
> >
> >The answer is that for transparency to work, you need to use Raytracing.
> >Shadow Maps can't determine transmission in glass-like materials,
> >transparency, or alpha maps. Turning on Shadow Transparency forces the
> light
> >type to be Raytraced, which is why you lose your soft shadows from Shadow
> >Map option (as it gets turned off).
> >
> >The solution is to create soft shadows using raytracing. There are
numerous
> >ways to do this. The most common is to use an array of lights, all
casting
> >raytraced shadows. You can create your own array, or use the Area light
or
> >IBL light (in the case of an IBL just scale it really small to act as a
> >small array, like a point light source that will give you soft shadows).
> >
> >Render times will go up in general, as raytracing shadows tends to take
> >longer, but this is the only way to get soft shadows from alpha maps.
> >
> >HTH!
> > Tom
> >
> >
> >
> >Thomas Moffat Grimes
> >Marketing Communications
> >Caligari Corporation
> >
> >mailto:thomas@(protected)
> >http://www.caligari.com
> >
> >-- --Original Message-- --
> >From: Visual Impact [mailto:visualimpact@(protected)]
> >Sent: Tuesday, April 06, 2004 3:13 AM
> >To: truespace@(protected)
> >Subject: [TSML] Shadow transperancy problems
> >
> >
> >I am having trouble with turning shadow transperancy on for a shadow
> >casting light.
> >I start off with nice shadows with soft blurry edges, but as soon as I
> >turn on shadow transparency I get harsh defined edges for the shadows.
> >I want to keep the soft shadows but still have my alpha masked planes
> >cast shadows.
> >Can anyone shed some light on this.
> >John Butcher
> >
> >
> >
>
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