[GEM-dev] render chains: positive vs. negative differences

james tittle tigital at mac.com
Tue Dec 6 23:50:47 CET 2005


On Dec 6, 2005, at 5:04 PM, IOhannes m zmoelnig wrote:

> james tittle wrote:
>> ...I've come across a stumbling block on the road to gem shader   
>> nirvana, and I'm not sure why it's happening ;-\
>> ...here's what's happening:  the "positive" render chains are   
>> rendered after the perspective and view have been changed in the   
>> gemwin, but "negative" render chains are always locked to the  
>> default  values for some reason?  It seems to me that they should  
>> also receive  the perspective and view messages in the same way  
>> the positive render  chains do...
>> ...Is there something here I'm not seeing?
>
> i introduced negative render-chains to explicitly do on-screen- 
> display. (e.g. you move the camera around, but want some  
> information to be always displayed)
> it might have been not the very best idea to do this with negative  
> render chains (but it is well documented (or so i thought), and  
> there should be no real drawbacks by this "abuse")

...thanks for reminding me ;-)  I've really been struggling with  
getting some non-typical shaders (like mandelbrot calculators) to  
work, and was afraid that the negative chains we're somehow throwing  
a wrench into the works...but now I've eliminated that, and they  
still don't work :-(  Something's weird about using gl_MultiTexCoord0  
& friends for passing in a position to the fragment shader...

...otoh, I don't recall seeing this in docs, so at least we can say  
"search the list" from now on if it comes up!

l8r,
jamie




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