Dynamic arrays on GLSL

I have worked with C++/OpenSceneGraph/GLSL integration and I need to handle dynamic array on shader.

My dynamic data array of vec3 was converted into 1D-texture to pass as uniform to fragment (I’m using GLSL 1.3), as follows:


    osg::ref_ptr<osg::Image> image = new osg::Image; 
    image->setImage(myVec3Array->size(), 1, 1, GL_RGBA8, GL_RGBA, GL_FLOAT, (unsigned char*) &myVec3Array[0], osg::Image::NO_DELETE);

    // Pass the texture to GLSL as uniform
    osg::StateSet* ss = scene->getOrCreateStateSet();
    ss->addUniform( new osg::Uniform("vertexMap", texture) ); 

For now, I would like to retrieve my raw array of vec3 on fragment shader. How can I do this process? Does a texture2D function only return normalized values?

Thanks in advance.

If you want to store floating-point values directly, the texture needs to have a floating-point internal format (e.g. GL_RGB32F). Floating-point textures require OpenGL 3.0 (which you should already have if you’re using GLSL 1.3) or the ARB_texture_float extension.

If you don’t need the full range and precision of IEEE-754 single-precision floats, you can use half-precision floats (e.g. GL_RGB16F), which have a 5-bit exponent and 10-bit significand.

If you want constant absolute error (rather than relative error), then you can use a normalised format or an integer format and perform the scaling in the fragment shader.

Hi GClements,

I will can handle the floating-point textures on C++/OSG side, however I still have a question: how can I access this floating-point values on shader side? Could you give me an example?

Thanks in advance.

Just use texture2D() etc. The values won’t be limited to [0,1] if the texture has a floating-point internal format.

Thanks, GClements.

GClements,

I’m facing with texture coordinate problem. I passed the floating matrix of vec3 as texture to shader, however I would like to retrieve these values there . Could you help me?

If you’re using a texture as an array, you should probably use texelFetch() to retrieve values. That avoids filtering and the need to convert indices to normalised texture coordinates.

It worked, GClements. Thanks!

This topic was automatically closed 183 days after the last reply. New replies are no longer allowed.