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Baker



Joined: 14 Mar 2006
Posts: 1538

PostPosted: Fri Jul 16, 2010 12:50 am    Post subject: r_mirroralpha question ... Reply with quote

To anyone who knows and is bored ...



What's r_mirroralpha doing exactly?

It is something like rendering to texture from the reverse visual angle it seen? Well, it can't be that precisely because it isn't doing a texture upload.

I suppose I can walk through it but it occurs to me that altering the r_mirroralpha code could be an awesome way to make a viewscreen in Quake by instead of rendering from it's own viewpoint, rendering from the viewpoint somewhere else in the map.

You could make a security camera so some such thing. I do wonder why some video cards (Radeons?) don't support r_mirroralpha. I could probably dig thru Google to find out what OpenGL thing it hates.

I might do some experiments and post shots here.
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Downsider



Joined: 16 Sep 2008
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PostPosted: Fri Jul 16, 2010 1:57 am    Post subject: Reply with quote

Biggest problem is the PVS and that you'd have to play with it to get it working in a networked game, I guess.
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Baker



Joined: 14 Mar 2006
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PostPosted: Fri Jul 16, 2010 2:48 am    Post subject: Reply with quote

Downsider wrote:
Biggest problem is the PVS and that you'd have to play with it to get it working in a networked game, I guess.


Good point. I wasn't thinking about that part. I was thinking entities.

Probably would require something like sv_novis even to do a good test.
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mk



Joined: 04 Jul 2008
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PostPosted: Fri Jul 16, 2010 2:49 am    Post subject: Re: r_mirroralpha question ... Reply with quote

Baker wrote:
It is something like rendering to texture from the reverse visual angle it seen?

Actually, GLQuake duplicates the whole scene's triangles, mirrors their positions accordingly to the mirror's position, and makes the mirror texture translucent. So, it's not a render-to-texture, it's more like the mirrors in Duke Nukem 3D.
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Baker



Joined: 14 Mar 2006
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PostPosted: Fri Jul 16, 2010 3:03 am    Post subject: Reply with quote

Part of the reason I want to understand it is that in my dx8pro build I get this [a build of my engine that uses MH's Direct 3D 8.1 wrapper]:



^^ Mirror texture appears thru wall.



^^ Player gets "mirrored".

I have some cool uses for mirror alpha I'd like to experiment with.

Anyways, your explanation is helpful and maybe I can play around now.
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leileilol



Joined: 15 Oct 2004
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PostPosted: Fri Jul 16, 2010 10:10 am    Post subject: Reply with quote

that's only bad alpha sorting

the way GLQuake does it is nothing special, and only breaks on very early cards (i.e. not Voodoo '96 hardware)
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