Re: [osg-users] Need help fixing my atmospheric transmission shader, it's so close to working!
I should have mentioned before that only the red channel is of any importance; There is a viewer further down the pipeline that picks up the red channel values from the framebuffer so the green and blue channels don't matter at all. I just set the green and blue channels to the red channel in case I ever want to use a different viewer and see things in grey-scale. I tried to do a bit of research on GLSL texture binding but am very confused by it and not sure what I could change about my shader to fix binding issues. I tried using this line: Code: vec4 color = texture2D(baseTexture, gl_TexCoord[0].st) + gl_Color; thinking that by adding the texture color to the tree colors I might get the correct result. This actually makes me see both the terrain texture and the tree colors. This may then be the correct solution, but I'm not sure if it is really doing what I think it's doing... -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=45118#45118 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Need help fixing my atmospheric transmission shader, it's so close to working!
Only your terrain have texture and for your trees - function call texture2D(baseTexture, gl_TexCoord[0].st) return black (0,0,0,1). Your trees have per-vertex color attribute, and your ground dont(?) (i dont know to what value it defaults). Simplest options to fix this - set 1x1 white texture to your trees or add color array to ground (with black color values) and use texture2D(baseTexture, gl_TexCoord[0].st) + gl_Color, or write different shaders (one version with texture, one without). If gl_Color defaults to black without color array, you can use vec4 color = texture2D(baseTexture, gl_TexCoord[0].st) + gl_Color; without any changes. 30.01.2012, 17:30, Ethan Fahy ethanf...@gmail.com: I should have mentioned before that only the red channel is of any importance; There is a viewer further down the pipeline that picks up the red channel values from the framebuffer so the green and blue channels don't matter at all. I just set the green and blue channels to the red channel in case I ever want to use a different viewer and see things in grey-scale. I tried to do a bit of research on GLSL texture binding but am very confused by it and not sure what I could change about my shader to fix binding issues. I tried using this line: Code: vec4 color = texture2D(baseTexture, gl_TexCoord[0].st) + gl_Color; thinking that by adding the texture color to the tree colors I might get the correct result. This actually makes me see both the terrain texture and the tree colors. This may then be the correct solution, but I'm not sure if it is really doing what I think it's doing... -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=45118#45118 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Need help fixing my atmospheric transmission shader, it's so close to working!
Hi
this piece completely eliminate any green and blue values of original color, if
you trees dont have red color component they will look black.
color.r = color.r * exp( -1.0 * ExtinctionCoefficient * eyeDistance );
color.g = color.r;
color.b = color.r;
Sampling texture when it not currently bound iirc should return (0,0,0,1), here
you get your black color (also this could cause crash on some drivers).
27.01.2012, 23:19, Ethan Fahy ethanf...@gmail.com:
My scene contains virtualplanetbuilder-generated terrain that has a texture
wrapped on it along with surface objects such as trees that I generated by
creating osg primitives and coloring them PER_VERTEX without using any
textures.
I have written an atmospheric transmission shader that decreases the r,g and
b values as a function of distance from the viewer to the object. However, I
can't seem to get the shader to work properly on both the terrain and trees
at the same time. Here is the code:
Vertex Shader:
Code:
varying float eyeDistance;
void main(void)
{
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_FrontColor = gl_Color;
eyeDistance = length(gl_ModelViewMatrix * gl_Vertex);
gl_Position = ftransform();
}
Fragment Shader:
Code:
uniform float ExtinctionCoefficient;
uniform sampler2D baseTexture;
varying float eyeDistance;
void main(void)
{
vec4 color = texture2D(baseTexture, gl_TexCoord[0].st);
color.r = color.r * exp( -1.0 * ExtinctionCoefficient * eyeDistance );
color.g = color.r;
color.b = color.r;
gl_FragColor = color;
}
The above shader pair will successfully make the terrain darker in color as I
zoom out, but the trees all look completely black no matter what, even if
they originally had varying colors without the shader.
If instead of setting color in the frag shader to texture2D() I instead set
it equal to gl_Color, the shader then works on all the objects in the scene
but I no longer see any remnants of the underlying terrain texture. Based on
this page
http://stackoverflow.com/questions/2552676/change-the-color-of-a-vertex-in-a-vertex-shader
I would have expected that setting color = texture2D(baseTexture,
gl_TexCoord[0].st) * gl_Color would have produced the result I was looking
for, but instead the result is identical to if I leave out * gl_Color.
I think my shader code is very close to being correct and just needs a nudge
in the right direction. Anyone?
Thanks very much in advance.
-Ethan
--
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http://forum.openscenegraph.org/viewtopic.php?p=45086#45086
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[osg-users] Need help fixing my atmospheric transmission shader, it's so close to working!
My scene contains virtualplanetbuilder-generated terrain that has a texture
wrapped on it along with surface objects such as trees that I generated by
creating osg primitives and coloring them PER_VERTEX without using any
textures.
I have written an atmospheric transmission shader that decreases the r,g and b
values as a function of distance from the viewer to the object. However, I
can't seem to get the shader to work properly on both the terrain and trees at
the same time. Here is the code:
Vertex Shader:
Code:
varying float eyeDistance;
void main(void)
{
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_FrontColor = gl_Color;
eyeDistance = length(gl_ModelViewMatrix * gl_Vertex);
gl_Position = ftransform();
}
Fragment Shader:
Code:
uniform float ExtinctionCoefficient;
uniform sampler2D baseTexture;
varying float eyeDistance;
void main(void)
{
vec4 color = texture2D(baseTexture, gl_TexCoord[0].st);
color.r = color.r * exp( -1.0 * ExtinctionCoefficient * eyeDistance );
color.g = color.r;
color.b = color.r;
gl_FragColor = color;
}
The above shader pair will successfully make the terrain darker in color as I
zoom out, but the trees all look completely black no matter what, even if they
originally had varying colors without the shader.
If instead of setting color in the frag shader to texture2D() I instead set
it equal to gl_Color, the shader then works on all the objects in the scene
but I no longer see any remnants of the underlying terrain texture. Based on
this page
http://stackoverflow.com/questions/2552676/change-the-color-of-a-vertex-in-a-vertex-shader
I would have expected that setting color = texture2D(baseTexture,
gl_TexCoord[0].st) * gl_Color would have produced the result I was looking for,
but instead the result is identical to if I leave out * gl_Color.
I think my shader code is very close to being correct and just needs a nudge in
the right direction. Anyone?
Thanks very much in advance.
-Ethan
--
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=45086#45086
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