[ODE] drawing a rotated plane?

[Kevin Reid]

> I rotated a plane.
> My question is, how could I draw this rotated plane. I'm using the 
> drawstuff libary, and if I rotate a plane the plane is physically 
> rotated, but is drawn as it has the normal vector (0,0,1) (my normal 
> vector is somthing like (-0.2, 0, 0.8) and I want the plane to be drawn
> with this rotation.)

Here's the code I use (vp is defined elsewhere, and is the camera
origin):

    dVector4 p;
    dVector3 x, y, z;
    
    // get plane equation
    dGeomPlaneGetParams(geom, p);
    
    // fill z with plane normal
    z[0] = p[0]; z[1] = p[1]; z[2] = p[2];
    dNormalize3(z);
    
    // construct basis
    dPlaneSpace(z, y, x);
    {
      // rotate to match plane's orientation
      GLdouble glm[16] = {
        x[0], x[1], x[2], 0,
        y[0], y[1], y[2], 0,
        z[0], z[1], z[2], 0,
        0,    0,    0,    1,
      };
      glMultMatrixd(glm);
    }
    /* now translate so that 0,0,0 in the final space is as near as
possible to the viewer in xy, and matches the plane equation in z */
    glTranslatef(
      x[0] * vp[0] + x[1] * vp[1] + x[2] * vp[2],
      y[0] * vp[0] + y[1] * vp[1] + y[2] * vp[2],
      p[3]
    );


-- 
Kevin Reid