[GEM-dev] Different Alpha Blending Methods in Alpha Object

[Cyrille Henry]

Le 24/11/2012 13:52, Jack a écrit :
> Le 23/11/2012 11:55, ch at chnry.net a écrit :
>>   Le jeu 22/11/12 21:15, "Jack" jack at rybn.org a écrit:
>>
>>>>> You can use the object
>>> [GEMglBlendFunc].
>>> yes, but i don't see any reason not to include it in
>>> the alpha object.
>>> Because it still exists in the [GEMglBlendFunc] :)
>> most Gem object could be replaced by GEMgl* stuff...
> Yep, and thanx to Gem to simplify the use of OpenGL.
>>
>>> Seriously, as Chris says it's better to use shaders now, it's more
>>> flexible.
>> i do not agree.
>> using shader, how would you do :
>> GL_ONE_MINUS_SRC_COLOR
>> you need the source color. a readback is not an option.
> In my mind i was thinking about textures operations with the use of two
> framebuffers if you need to capture the scene.
> With this solution, you can determine the source and destination in your
> fragment shader (as glBlendFunc) then operate on destination something
> equivalent to GL_ONE_MINUS_SRC_COLOR, or i miss something and i am wrong ?
> If this solution is OK, you needn't readback...
yes, you're right, you don't need readback if you use framebuffer.
but it would still be lot's more complex do to something like :

gemhead
alpha
repeat 100
separator
color 1 1 1 0.1
translate (few random)
square

cheers
c



>> moreover, it's lot's easier to try sending diferent number in the alpha object to see the result, than to write a shader.
> Yes, i agree it is easier to use directly Gem objects (objects different
> than [GEMgl*])...
>> and if you don't need this functionality, you don't have to use it...
>>
>> So,i think it would be nice to have this small modification included in Gem.
> Sure.
> ++
>
> Jack
>
>
>> cheers
>> c
>>
>>
>> ++
>>> Jack
>>>
>>>
>>>> cheers
>>>> c
>>>>
>>>>> ++
>>>>>
>>>>> Jack
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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