[osg-users] Help: how to getmore than four elements via fragment shader?

[wang shuiying]

Hello,

  I want to record more than four elements by writing to "out variable" 
in fragment shader.

 I notice that FBO can connect to many buffers, so I define two images 
which are respectively attached to a color buffer and a depth buffer.

osg source code are as follows:

  osg::Image *imageDepth=new osg::Image();
   imageDepth->allocateImage((int)subXRes, (int)subYRes, 1, GL_RGBA, 
GL_FLOAT);
  camera->attach(osg::CameraNode::DEPTH_BUFFER, imageDepth);

osg::Image * image = new osg::Image();
image->allocateImage((int)subXRes, (int)subYRes, 1, GL_RGBA, GL_FLOAT);
camera->attach(osg::CameraNode::COLOR_BUFFER, image);

fragment shader is as follows:

  gl_FragColor = vec4(1,0,0,1);

gl_FragDepth=0.3;

But it doesn't work: application output:
Warning: detected OpenGL error 'invalid operation' at after 
RenderBin::draw(..)

 then I change the internal format of imagedepth to GL_DEPTH. it still 
doesn't work. and the system says, the framebuffer is attatched to an 
empty image.

So how can I get more than four elements via fragment shader?

Thank you very much in advance!

Shuiying



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