2010/1/7 J.P. Delport <jpdelp...@csir.co.za <mailto: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> <mailto: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>> <mailto: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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