[PD] glsl effect chaining

[Hans-Christoph Steiner]

Nice, that one just worked for me.  It would be even more fun with a  
video camera.  I couldn't get that one going...

.hc

On Mar 21, 2008, at 10:18 PM, marius schebella wrote:

> hi,
> I put an example patch for chaining glsl shader modules at
> http://www.parasitaere-kapazitaeten.net/Pd/shader_chain
> it uses one of cyrille's shader examples.
> marius.
>
> marius schebella wrote:
>> yes, but...
>> it works, but you have to think about a lot of things and when it  
>> really
>> comes to chaining separate modules together it really gets  
>> complicated.
>> your gemchain has to look like this:
>>
>> [gemhead 49]
>>  |
>> [shader]
>>  |
>> [gemframbuffer]
>>  |
>> [translateXYZ 0 0 -4]
>>  |
>> [some...texture]
>>  |
>> [square 4]
>>
>> always give the gemhead a number smaller than the consecutive  
>> gemheads,
>> so that the textures are created before they are used in the next  
>> gemchain.
>> in the gemchain itself the shader has to be placed *before* the
>> framebuffer!
>> gemframebuffer always "resets" the viewpoint, so you have to  
>> translate
>> everything into negative z to make it visible.
>> texture needs mode 1 on some cards and mode 0 on other cards, this  
>> also
>> has to be the same as in the shader (sample2D v. sample2DRect).
>> the geo has to correlate with the translate and cover the whole  
>> range,
>> otherwise you wil crop the image or it will be too small.  
>> gemframebuffer
>> also takes an argument "dim" that will affect the quality.
>>
>> if you have all that then you can send the right outlet of
>> gemframebuffer (which is a number) to another texture right inlet and
>> another shader can use that.
>>
>> this is a little complicated but will work for a shader chain patch.
>>
>> now when you think about a modular shader system, where you can  
>> just add
>> shader abstraction into a chain, it gets much much more complicated.
>> because when you have a combination like
>>
>> [shader]
>>  |
>> [pix_image]
>>  |
>> [texture]
>>
>> then the right inlet of texture can get any number, the shader will
>> always take the image instead, so you cannot do your usual chains,  
>> but
>> will have to refer an image from somewhere else.
>> it is also difficult to debug, because the gemframebuffer will not
>> output a texture...
>> and then - if you use multiple shader modules - you also have to  
>> change
>> the renderorderof the gemhead. with [set 40( or something, but how do
>> you know at which position you use the shader module??...
>>
>> a solution for this would be to turn gemheads off and only trigger  
>> them
>> by "bang" messages.
>>
>> ok, the only thing missing right now is a patch showing how this  
>> works
>> in practice. I will do my best...
>>
>> marius.
>>
>>
>> cyrille henry wrote:
>>>
>>> Pepa Henzl a écrit :
>>>> Hello,
>>>> I've just started with glsl languague and Gem this week. Everything
>>>> works fine, but i'd like to know what to do if i want to apply
>>>> multiple effects on a texture.
>>>> Is it possible to render pix data to the texture, instead of  
>>>> current
>>>> framebuffer window,  and use it for further processing?
>>> yes.
>>> you need to render in a frambuffer, and then use it as a texture.
>>> the gemframebuffer is almost undocumented, but there is an  
>>> exemple in
>>> exemple/07.texture/10.frambuffer.
>>>
>>> i also rembermber that i send a patch on this list (or gem-dev)
>>> regardinf the use of glsl + framebuffer.
>>>
>>> cyrille
>>>
>>>
>>>> Thanks,
>>>> pcp.
>>>>
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>>
>
>
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