[osg-users] Post Processing Effect - Vertex Shader not working

[Volckaert, Guy (CA - MTS)]

Hi,

Sorry to bother you guys... but I was wondering if you can help identify why my pass through vertex shader isn't working. In essence, if I enable the vertex shader, then the scene disappears (I only see that blue background color). If I disable it then the scene appears correctly. No errors are generated by OSG after linking the vertex shader. I know that my fragment shader is working because if I set the gl_FragColor to red then the scene is completely red.

Here are my pass-thru shaders:

[code]
VERTEX SHADER
=============
attribute vec4 osg_Vertex;
void main( void )
{
     gl_Position = osg_Vertex;
}

FRAGMENT SHADER
===============
uniform sampler2D tRttTexture;

void main( void )
{
     vec3 vColor = texture2D( tRttTexture, gl_TexCoord[0].st ).rgb;
     // Output color.
     gl_FragColor = vec4( vColor, 1.0 );
}
[/code]


The shader is applied on a fullscreen quad using typical Ortho2D projection. Here is the code that loads the shader which is applied to the post process geode containing a single geometry quad:

[code]
void loadShaders( )
{
    osg::StateSet* pStateSet = g_pPolyGeode->getOrCreateStateSet( );

    osg::ref_ptr<osg::Program> pProgram = new osg::Program;
    pProgram->setName( "PostProcessProgram" );

    osg::ref_ptr<osg::Shader> pVertShader = osg::Shader::readShaderFile( osg::Shader::VERTEX, osgDB::findDataFile( "shaders/osgprerender.vert" ) );
    if( pVertShader )
    {
        pVertShader->setName( "osgprerender.vert" );
        pProgram->addShader( pVertShader );
        pProgram->addBindAttribLocation( "osg_Vertex", 0 );
    }

    osg::ref_ptr<osg::Shader> pFragShader = osg::Shader::readShaderFile( osg::Shader::FRAGMENT, osgDB::findDataFile( "shaders/osgprerender.frag" ) );
    if( pFragShader )
    {
        pFragShader->setName( "osgprerender.frag" );
        pProgram->addShader( pFragShader );
    }

    // RTT texture.
    pStateSet->addUniform( new osg::Uniform( "tRttTexture", 0 ) );
    pStateSet->setAttributeAndModes( pProgram, osg::StateAttribute::ON );
}
[/code]


What am I doing wrong? I tried different variation of the shader but nothing works. Here are the variations that I tried:

[code]
VARIATION #1
===========
void main( void )
{
     gl_Position = gl_Vertex;
}

VARIATION #2
===========
void main( void )
{
     gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}

VARIATION #3
===========
attribute vec4 osg_Vertex;
void main( void )
{
     gl_Position = gl_ModelViewProjectionMatrix * osg_Vertex;
}

VARIATION #4
===========
void main( void )
{
     gl_Position = ftransform();
}
[/code]

Any help would be really appreciated... The full source code is attached.

Thank you!

Cheers,
Guy

Guy Volckaert, ing.
Snr Software Engineer

Meggitt Training Systems (Quebec) Inc.
Systèmes d'entraînement Meggitt (Québec) Inc.
6140 Henri Bourassa West
Montreal, Quebec, H4R 3A6
Canada

Tel: 1 (514) 339 9938 Ext 617
Fax: 1 (514) 339 2641
Cell: 1 (514) 928-5641
email: guy.volckaert at meggitt.com<mailto:brian.bakker at meggitt.com>
url; www.meggitt.com<http://www.meggitt.com>
skype: guy.volckaert

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