Thanks for the link, i will look at this.
But for the shader example I gave you I think that it do the first treatment
for the first pixel then it peel the first layer and do the second
treatment for the second depth layer, but maybe I wrong.
The code of osgoit is it available somewhere?
2010/1/7 J.P. Delport <jpdelp...@csir.co.za>
> Hi,
>
>
> clement vidal wrote:
>
>> Thanks for your help.
>>
>> But the solution that you gave me it's not really what I want to do. The
>> simple example i gave you it's just to explain what kind of result I need.
>> Actually I'm trying to implement a Dual Depth Peeling based on the Nvidia
>> Paper and it use this kind of blending. For example in my shader if I do
>> that:
>>
>> int i=0;
>>
>> void main()
>> {
>> if(i=0)
>> {
>> gl_FragData[0 = vec4(1.0,0.0,0.0,1.0);
>>
>> i=1;
>> return;
>> }
>> gl_FragData[0] = vec4(0.0,1.0,0.0,1.0);
>> }
>>
>> I would like have yellow in my texture for now I have green. Here again
>> it's just an example, but that's why i would like to use a blend equation,
>> it's the same problem as the other example I gave you I would like do a MAX
>> blending between the value previously in the texture and the new value.
>>
>> Have you an idea how to do that?
>>
>
> Well your shader only executes once... so AFAIK you can only write once to
> the frame buffer in a render pass.
>
> If you want colours to blend with previous ones you first have to create
> the previous ones, so you will need multiple passes.
>
> Maybe also see here for inspiration:
> http://thread.gmane.org/gmane.comp.graphics.openscenegraph.cvs/6263/
>
> jp
>
>
>>
>> 2010/1/7 J.P. Delport <jpdelp...@csir.co.za <mailto:jpdelp...@csir.co.za
>> >>
>>
>> Hi Clement,
>>
>>
>> clement vidal wrote:
>>
>> 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.
>>
>>
>> OK I think I understand better now. To use your texture as input (in
>> order to kind of make it the background (as you have working with
>> clearcolour)) you will have to map it onto a quad (screen/camera
>> projection aligned) [1]. Then you make your camera look at this quad
>> and the fragment shader would then blend with the texture in the
>> frame buffer. Reading from and writing to the same texture can
>> sometimes give problems, so you might have to make a copy for the
>> output (ping-pong, see osggameoflife).
>>
>> I'm also not sure why you want to use blending, do you have some
>> special algorithm that needs it? If you have an initial texture with
>> input values, you can just sample it in your shader and modify the
>> value yourself (based on maths, input uniforms or other textures)
>> and put it into the final texture.
>>
>> [1] Attachments to the camera are outputs, textures bound to
>> geometry are used as inputs for RTT.
>>
>> cheers
>> jp
>>
>>
>>
>>
>> Thanks for your help
>>
>> Clement
>>
>> 2010/1/7 J.P. Delport <jpdelp...@csir.co.za
>> <mailto:jpdelp...@csir.co.za> <mailto:jpdelp...@csir.co.za
>>
>> <mailto: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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