Re: Identifying a Tangents Property

[André Adam <a_adam(at)49games.de>]

Brilliant, just saw the puzzled expression being replaced by immediate 
understanding...

Many thanks, that was very welcome and valuable help! Cheers!

   -André


Alexandre Jean-Claude wrote:
> Oook, I understand. So
>
> Vertex Color RGB = (Tangent XYZ /2) + 0.5
> The alpha is actually the sign of the tangent, basically just unbias the alpha (alpha *2 +1) and multiply it by the tangent value to sign it properly. 
>
> I'll send a sample to show everyone how to do it. I agree this is something we should document in more details. I'll try to post it today if possible.
>
>
>
>
>
>
>  
>
> -----Original Message-----
> From: owner-3dgames(at)Softimage.COM [mailto:owner-3dgames(at)Softimage.COM] On Behalf Of André Adam
> Sent: Thursday, December 07, 2006 11:12 AM
> To: 3DGames(at)Softimage.COM
> Subject: Re: Identifying a Tangents Property
>
> We don't want to recompute them, it's just that our own pixel shaders currently don't like XSI's tangents and to fix this it would be helpful if the methods used to create it are documented somewhere. At least that's how I understand it, I've a programmer over here with a slightly puzzled expression in his face and that worries me... ;) Really, we only need a pointer just in case there is public documentation available. If there isn't, he'll just have to spend a night or so to debug his code without additional hints...
>
> What still is of direct interest is the alpha channel written to the tangents property. Currently nobody over here has a clue what to with it. On the other hand, perhaps this is the source of the problem...
>
> Better? Thanks for your patience! :)
>
>     -André
>
>
> Alexandre Jean-Claude wrote:
>   
> > Out of curiosity, why do you need to recompute them if you already have the data ? 
> >
> >  
> >
> > -----Original Message-----
> > From: owner-3dgames(at)Softimage.COM [mailto:owner-3dgames(at)Softimage.COM] 
> > On Behalf Of André Adam
> > Sent: Thursday, December 07, 2006 10:55 AM
> > To: 3DGames(at)Softimage.COM
> > Subject: Re: Identifying a Tangents Property
> >
> > How it is calculated. :)
> >
> >
> > Alexandre Jean-Claude wrote:
> >   
> >     
> > > You mean how it's calculated or how it is encoding the tangent ? 
> > >
> > >  
> > >
> > > -----Original Message-----
> > > From: owner-3dgames(at)Softimage.COM 
> > > [mailto:owner-3dgames(at)Softimage.COM]
> > > On Behalf Of André Adam
> > > Sent: Thursday, December 07, 2006 10:43 AM
> > > To: 3DGames(at)Softimage.COM
> > > Subject: Re: Identifying a Tangents Property
> > >
> > > Ok, I see... ... ;) Btw, we really like the XSI tangent space, thus the efforts to clearly identify it.
> > > While we're at it, is it somewhere documented in detail? Our programmers currently try to demystify the values to feed it to our engine, and I see them twisting and wrangling our UVs on a trial and error basis to make all of this fit together somehow...
> > >
> > > Cheers!
> > >
> > >     -André
> > >
> > >
> > > Alexandre Jean-Claude wrote:
> > >   
> > >     
> > >       
> > > > The heuristic we use in the dotXSI exporter in this case is to strstr for "tangent" in the vertex color prop. We also have an option to turn it off.
> > > >  
> > > >
> > > > -----Original Message-----
> > > > From: owner-3dgames(at)Softimage.COM
> > > > [mailto:owner-3dgames(at)Softimage.COM]
> > > > On Behalf Of André Adam
> > > > Sent: Thursday, December 07, 2006 6:33 AM
> > > > To: 3DGames(at)Softimage.COM
> > > > Subject: Re: Identifying a Tangents Property
> > > >
> > > > Hi Alexandre,
> > > >
> > > > thanks, however, the magic must be a different one. Checking for the op fails for frozen objects, while the dotXSI exporter still manages to identify it as a tangent property. Another idea left in the quiver?
> > > >
> > > > Many thanks so far!
> > > >
> > > >     -André
> > > >
> > > >
> > > > Alexandre Jean-Claude wrote:
> > > >   
> > > >     
> > > >       
> > > >         
> > > > > You need to check for the tangent operator underneath the vertex color. 
> > > > >
> > > > > -----Original Message-----
> > > > > From: owner-3dgames(at)Softimage.COM
> > > > > [mailto:owner-3dgames(at)Softimage.COM]
> > > > > On Behalf Of André Adam
> > > > > Sent: Wednesday, December 06, 2006 6:07 AM
> > > > > To: 3dgames(at)Softimage.COM
> > > > > Subject: Identifying a Tangents Property
> > > > >
> > > > > Hello alltogether,
> > > > >
> > > > > we're currently playing around with the tangents property generated by XSI. If exported to dotXSI5, the Type description is "TEXTANGENT". 
> > > > > However, within XSI the Type returns "vertexcolor". We can't seem to find any hint on that property within XSI to clearly identify it as a tangents property, which we would like to do to pass it over to our Custom Display Host.
> > > > > Obviously this is possible, so, how does the dotXSI exporter identify it as a tangents property?
> > > > >
> > > > > Oh, and if anyone has any idea what kind of information is stored 
> > > > > in the alpha channel during tangent generation, that would be an 
> > > > > interesting extra bit of information... :)
> > > > >
> > > > > Thanks in advance for a quick hint...
> > > > >
> > > > >     -André
> > > > >           
>
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