Can we use other openGL methods?  For example, I want to clear the z-buffer, and I tried writing this code but it doesn't work (I'm still shakey with opengl, so this might just be bad code):

PGraphicsGL PGL;

void initGLEx()
{
 PGL = (PGraphicsGL)g;
 clearBuffer = new float[height*width];
 for (int i=0; i<clearBuffer.length; i++)
 {
   clearBuffer[i] = 1;
 }

}

void glClearDepthBuffer()
{
 PGL.gl.glRasterPos2f(0.0,0.0);
 PGL.gl.glDrawPixels(width,height,PGL.gl.GL_DEPTH_COMPONENT,
                   PGL.gl.GL_FLOAT,clearBuffer);
}