- glMatrixMode(GL_MODELVIEW);
- glPushMatrix();
- glLoadIdentity();
-
- // Generate a "look at" matrix using OpenGL (!) coordinate
- // conventions.
- float lookat[3];
- float pitch = view->getPitchOffset_deg() * SGD_DEGREES_TO_RADIANS;
- float rot = view->getHeadingOffset_deg() * SGD_DEGREES_TO_RADIANS;
- lookat[0] = -sin(rot);
- lookat[1] = sin(pitch) / cos(pitch);
- lookat[2] = -cos(rot);
- if(fabs(lookat[1]) > 9999) lookat[1] = 9999; // FPU sanity
- gluLookAt(0, 0, 0, lookat[0], lookat[1], lookat[2], 0, 1, 0);
-
- // Translate the origin to the location of the panel quad
- glTranslatef(a[0], a[1], a[2]);
-
- // Generate a matrix to translate unit square coordinates from the
- // panel to real world coordinates. Use a transposed basis for
- // the panel quad. Note: this matrix is relatively expensive to
- // compute, and is invariant. Consider precomputing and storing
- // it. Also, consider using the plib vector math routines, so the
- // reuse junkies don't yell at me. (Fine, I hard-coded a cross
- // product. Just shoot me and be done with it.)
- float u[3], v[3], w[3], m[16];
- for(i=0; i<3; i++) u[i] = b[i] - a[i]; // U = B - A
- for(i=0; i<3; i++) v[i] = c[i] - a[i]; // V = C - A
- w[0] = u[1]*v[2] - v[1]*u[2]; // W = U x V
- w[1] = u[2]*v[0] - v[2]*u[0];
- w[2] = u[0]*v[1] - v[0]*u[1];
-
- m[0] = u[0]; m[4] = v[0]; m[8] = w[0]; m[12] = 0; // |Ux Vx Wx|
- m[1] = u[1]; m[5] = v[1]; m[9] = w[1]; m[13] = 0; // m = |Uy Vy Wy|
- m[2] = u[2]; m[6] = v[2]; m[10] = w[2]; m[14] = 0; // |Uz Vz Wz|
- m[3] = 0; m[7] = 0; m[11] = 0; m[15] = 1;
- glMultMatrixf(m);
-
- // Finally, a scaling factor to map the panel's width and height
- // to the unit square.
- glScalef(1./_width, 1./_height, 1);
-
- // Now, turn off the Z buffer. The panel code doesn't need
- // it, and we're using different clip planes anyway (meaning we
- // can't share it without glDepthRange() hackery or much
- // framebuffer bandwidth wasteage)
- glDisable(GL_DEPTH_TEST);