[Sidefx-houdini-list] unpremultiplied rendering?

Ben Schrijvers ben.schrijvers at guerrilla-games.com
Tue Jul 20 04:31:40 EDT 2010


And when using the COP option be sure to render to float point images as 
un-premultiply on an 8 bit image can result in nasty colors.

cheers,
benS

Peter Bowmar wrote:
> The problem is, it's extra unneeded processing.
>
> Any time a compositor wants to colour correct something, they do it on
> unpremultiplied imagery, then mult by alpha  afterwards. So, really,
> the renderer should put out unpremultiplied if possible to avoid extra
> processing. IMO :)
>
> Cheers,
>
> Peter B
>
> On 19 July 2010 08:51, Andrew D Lyons <tstexture at gmail.com> wrote:
>   
>> I would agree the shader is the wrong place to do it. Similarly - I'm not
>> convinced that the ROP option would be much better.
>>
>> The COP option is the best IMHO. Taunt them that the Houdini compositor can
>> handle it and their compositor can't, and see how fast they decide they can
>> do it. ;)
>>
>> Cheers
>>
>>
>> On 19 July 2010 08:44, katrin schmid <Katisss at gmx.de> wrote:
>>
>>     
>>> hi,
>>> while this is possible i dont intend
>>> to hard code it into the shaders.
>>> Hm, even an option in the shader seems the wrong place really.
>>> We are looking for the option but i do think
>>> we want a choice. I try the Cop and see what its used for.
>>> Thanks for your help,
>>> katrin
>>>
>>>
>>> -------- Original-Nachricht --------
>>>       
>>>> Datum: Mon, 19 Jul 2010 08:38:30 -0700
>>>> Von: Andrew D Lyons <tstexture at gmail.com>
>>>> An: sidefx-houdini-list at sidefx.com
>>>> Betreff: Re: [Sidefx-houdini-list] unpremultiplied rendering?
>>>>         
>>>> If you have access to your shader code you could divide your color output
>>>> by
>>>> your alpha prior to output. That should do it.
>>>>
>>>> On 18 July 2010 22:53, katrin schmid <Katisss at gmx.de> wrote:
>>>>
>>>>         
>>>>> hi,
>>>>> i have been asked to unpremultiply passes post render.
>>>>> Which sort of lets me wonder if we i couldnt render this way in first
>>>>> place.
>>>>> Anybody know how to do this?
>>>>> Best Regards,
>>>>> katrin
>>>>>
>>>>> --
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>>>>>           
>>>>
>>>> --
>>>> =======================================
>>>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>>>> =======================================
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>>>>         
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>>>       
>>
>> --
>> =======================================
>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>> =======================================
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>>     
>
>
>
>   




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