Hi Robert,
Thank you for replying.
Here is the example code.
shader1.vert
Code:
#version 120
varying vec4 v_color;
void main()
{
v_color = gl_Color;
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}
shader2.vert
Code:
#version 120
uniform mat4 u_viewMatrix;
uniform mat4 u_projMatrix;
uniform mat4 osg_ViewMatrixInverse;
varying vec4 v_color;
mat4 getModelToWorldMatrix()
{
return osg_ViewMatrixInverse * gl_ModelViewMatrix;
}
void main()
{
v_color = gl_Color;
gl_Position = u_projMatrix * u_viewMatrix * getModelToWorldMatrix() *
gl_Vertex;
}
shader.frag
Code:
#version 120
varying vec4 v_color;
void main()
{
gl_FragColor = v_color;
}
main.cpp
Code:
#include <osgDB/ReadFile>
#include <osgViewer/Viewer>
#include <osg/StateAttributeCallback>
#include <osg/Shape>
#include <osg/ShapeDrawable>
class StateNodeCallback : public osg::StateSet::Callback
{
public:
StateNodeCallback(osg::Camera *mainCamera) : _mainCamera(mainCamera) {}
virtual void operator () (osg::StateSet*ss, osg::NodeVisitor*nv)
{
ss->getUniform("u_projMatrix")->set(osg::Matrixf(_mainCamera->getProjectionMatrix()));
ss->getUniform("u_viewMatrix")->set(osg::Matrixf(_mainCamera->getViewMatrix()));
}
private:
osg::ref_ptr<osg::Camera> _mainCamera;
};
osg::Geode *createCylinder(const osg::Vec4 &color)
{
osg::ref_ptr<osg::Cylinder> cylinder = new osg::Cylinder;
cylinder->setHeight(10.0f);
osg::ref_ptr<osg::ShapeDrawable> sd = new osg::ShapeDrawable;
sd->setShape(cylinder);
sd->setColor(color);
osg::ref_ptr<osg::Geode> geode = new osg::Geode;
geode->addDrawable(sd);
return geode.release();
}
int main()
{
osgViewer::Viewer viewer;
osg::ref_ptr<osg::Geode> cylinder1 = createCylinder(osg::Vec4(1, 0, 0,
1));
osg::ref_ptr<osg::Geode> cylinder2 = createCylinder(osg::Vec4(0, 1, 0,
1));
osg::ref_ptr<osg::Program> shader1 = new osg::Program();
shader1->addShader(osgDB::readShaderFile("shader1.vert"));
shader1->addShader(osgDB::readShaderFile("shader.frag"));
osg::ref_ptr<osg::Program> shader2 = new osg::Program();
shader2->addShader(osgDB::readShaderFile("shader2.vert"));
shader2->addShader(osgDB::readShaderFile("shader.frag"));
osg::ref_ptr<osg::Group> group1 = new osg::Group();
osg::ref_ptr<osg::Group> group2 = new osg::Group();
group1->addChild(cylinder1);
group2->addChild(cylinder2);
group1->getOrCreateStateSet()->setAttributeAndModes(shader1,
osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
group2->getOrCreateStateSet()->setAttributeAndModes(shader2,
osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
osg::ref_ptr<osg::Camera> mainCamera = viewer.getCamera();
group2->getOrCreateStateSet()->setUpdateCallback(new
StateNodeCallback(mainCamera));
group2->getOrCreateStateSet()->addUniform(new
osg::Uniform("u_projMatrix", osg::Matrixf(mainCamera->getProjectionMatrix())));
group2->getOrCreateStateSet()->addUniform(new
osg::Uniform("u_viewMatrix", osg::Matrixf(mainCamera->getViewMatrix())));
osg::ref_ptr<osg::Group> root = new osg::Group();
root->addChild(group1);
root->addChild(group2);
viewer.setSceneData(root);
viewer.run();
}
Make sure to set OSG_RUN_MAX_FRAME_RATE environment variable to a low value,
like 20, in order to better expose this issue.
I also attached a screen shot and the source code
...
Thank you!
Robin
robertosfield wrote:
> Hi Robin,
>
>
> I'm a bit perplexed by the issue, as the uniform should be tracking the
> modelview matrix directly as osg::State does a substitution.
>
>
> Could you create a small code example that reproduces the problem?
>
>
> Robert.
>
>
> On 25 March 2015 at 01:28, Robin Wu < ()> wrote:
>
> > Hi all,
> >
> > Recently, I discovered a weird issue that the view/Proj matrix in the main
> > camera updated by the default cameramanipulator of osgViewer does not sync
> > with the one I got in the shader, e.g gl_ModelViewMatrix,
> > gl_ProjectionMatrix.
> >
> > The following two code snippets produce different results.
> > The first one is using the built in gl_ModelViewProjectionMatrix uniform
> > passed in during renderingTraversals()
> >
> > The second one is using the properties from _viewer->getCamera() as
> > uniforms, e.g mainCamera->getViewMatrix().
> >
> >
> > Code:
> >
> > void main()
> > {
> > gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
> > }
> >
> >
> >
> >
> >
> > Code:
> >
> > uniform mat4 u_modelMatrix;
> > uniform mat4 u_viewMatrix;
> > uniform mat4 u_projMatrix;
> >
> > mat4 getModelToWorldMatrix()
> > {
> > return osg_ViewMatrixInverse * gl_ModelViewMatrix;
> > }
> >
> > void main()
> > {
> > gl_Position = u_projMatrix * u_viewMatrix * getModelToWorldMatrix() *
> > gl_Vertex;
> > }
> >
> >
> >
> >
> > When overlapping the rendering results of the two shaders into one buffer,
> > the second shader is approximately one frame slower than the first one,
> > making me doubt that the view/proj matrix managed by the main camera is not
> > synced with the one managed by the renderingTraversals().
> >
> > This out of sync problem is also pronounced in Wang Rui's effectcompositor.
> > In the ssao.xml demo, if you turn on the analysis mode, you'll see that in
> > the linearDepth buffer view, the depth is unstable (flickering) when you
> > zoom in and out quickly.
> >
> > The following is the code snippet from Rui's ssao.xml
> >
> > Code:
> >
> > void main(void)
> > {
> > vec4 vecInEye = gl_ModelViewMatrix * gl_Vertex;
> > depthValue = (-vecInEye.z - nearPlaneValue) / (farPlaneValue -
> > nearPlaneValue);
> > gl_Position = ftransform();
> > }
> >
> >
> >
> >
> > I suspect that the nearPlaneValue and farPlaneValue form the built-in
> > projection matrix's uniforms are somehow not synced with the corresponding
> > ones in gl_ProjectionMatrix ( from ftransfrom() );
> >
> > This problem bugs me for a long time. My current workaround is just using
> > the manually supplied uniforms from the main camera. But the extra
> > computation of the modelviewprojecionmatrix is definitely a waste in the
> > vertex shader.
> >
> > Any ideas?
> >
> > Thank you.
> >
> > ...
> >
> > Robin[/code]
> >
> > ------------------
> > Read this topic online here:
> > http://forum.openscenegraph.org/viewtopic.php?p=63199#63199
> > (http://forum.openscenegraph.org/viewtopic.php?p=63199#63199)
> >
> >
> >
> >
> >
> > _______________________________________________
> > osg-users mailing list
> > ()
> > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> > (http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org)
> >
>
>
> ------------------
> Post generated by Mail2Forum
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=63212#63212
Attachments:
http://forum.openscenegraph.org//files/osg_issue_207.png
http://forum.openscenegraph.org//files/osgexample_163.zip
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