Shadow transperancy problems 2004-04-09 - By Thomas Moffat Grimes
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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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