Thanks for your answer but I already use multi pass render with RTT. That I
would like to do it's to make a blending between the value witch is already
in the texture and the news value I put in with the shader, that in the same
pass. I want to do that because with my shader I access multiple time to the
same texture (one time by peeled layer) and I want the max value of all the
layers i peel.
2010/1/7 Julien Valentin <julienvalenti...@gmail.com>
> Hi there,
> If i understand you want to do render to texture (RTT) pass:
> You have several choice in order to do that. I give you the more classic
> RTT with multitexturing:
>
> //need 3 textures texA &texB input values and TexC binded to camera via fbo
> uniform sampler2D texA;
> uniform sampler2D texB;
>
> void main(){
> vec4 color1=sample(texA,texcoord.x,texxcoordy);
> vec4 color2=sample(texA,texcoord.x,texxcoordy);
>
> //you blending function
> gl_fragcolor=color1*(color1.a)+color2*color2.a*(1-color1.a);
> }
>
> The only thing you have to do is to declare a camera on prerender step
> whose frame buffer is attached to the texC and bind shader parameters to
> texA and texC
> Hope it will fit your usage ( see osggameoflife for RTT)
>
>
>> Hi JP
>>
>> For now I Initialize a texture with the value A, in the shader I put the
>> value B and I would like to have a the end in the texture the max blending
>> between the value A and B.
>>
>> Lets do an example:
>>
>> I create an texture Tex initialized with color red (1,0,0,1)
>>
>> I attach my texture to a camera Camera->attach(osg::Camera::COLOR_BUFFER0,
>> Tex);
>>
>> I use a shader witch do this treatment: gl_FragData[0] =
>> vec4(0.0,1.0,0.0,1.0);
>>
>> And I would like have a yellow (1.0,1.0,0.0,1.0) texture at the end of the
>> treatment.
>>
>> For now using an osg::BlendEquation with RGBA_MAX blending, I have if I
>> define a clearColor to my camera the blending between this clearColor and
>> the color use in the shader. I think this is normal because the
>> blendEquation define how the blending is doing between the color
>> previously
>> in the frame buffer and the added color. But it's not what i want I would
>> like to have the blending between the color previously in the texture and
>> the added color.
>>
>> Thanks for your help
>>
>> Clement
>>
>> 2010/1/7 J.P. Delport <jpdelp...@csir.co.za>
>>
>> > Hi Clement,
>> >
>> > could you explain a bit more what you expect and what you are getting?
>> Do
>> > you want to blend between the different textures (AFAIK you cannot do
>> this
>> > unless you do another pass)? Are you expecting max, but getting average?
>> >
>> > jp
>> >
>> > clement vidal wrote:
>> >
>> >>
>> >> Hi,
>> >>
>> >> I have a problem with BlendEquations and shaders. That is the
>> situation:
>> >>
>> >> I attach several textures to my camera using COLOR_BUFFER0,
>> >> COLOR_BUFFER1, ...
>> >> I use a shader to make the rendering into this textures.
>> >>
>> >> There is some values in this textures and i would like to use a max
>> >> blending between the value wich are already in and the values i affect
>> in
>> >> the shader.
>> >>
>> >> When I define an osg::BlendEquation with RGBA_MAX blending, i have the
>> >> blend result between the value in the frame buffer (background color or
>> >> ClearColor ) and the value in the shader.
>> >>
>> >> What I do wrong? Somebody have a idea?
>> >>
>> >> Thanks for helping
>> >>
>> >>
>> >>
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