/*
         * TODO STEP 31: Set glColorMask and glDepthMask to false. Enable the
         * stencil test.
         */
        gl.glColorMask(false, false, false, false);
        gl.glDepthMask(false);
        gl.glEnable(GL10.GL_STENCIL_TEST);


        /*
         * TODO STEP 32a: Set the stencil function to always pass. Use 1 as
         * reference value. Set bitmask to ~0.
         */
        gl.glStencilFunc(GL10.GL_ALWAYS, 1, 0);

        /*
         * TODO STEP 32b: Set the stencil operation to GL_REPLACE to replace the
         * current value in the stencil buffer. As the stencil test always
         * passes the value for stencil fail does not matter.
         */
        gl.glStencilOp(GL10.GL_REPLACE, GL10.GL_REPLACE, GL10.GL_INCR);

        /*
         * TODO STEP 13b: Draw the floor and execute the application!
         */
        mFloor.draw(gl);

        /*
         * TODO STEP 33: Set glColorMask and glDepthMask to true and draw the
         * floor a second time. As the stencil function has been inserted, the
         * first call causes the floor to be drawn into the stencil buffer but
         * not on the display anymore.
         */
        gl.glColorMask(true, true, true, true);
        gl.glDepthMask(true);
        mFloor.draw(gl);


        /*
         * TODO STEP 34a: Change the stencil function to be true when the value
         * in the stencil buffer equals 1 (GL_EQUAL 1). Set the bitmask to ~0
         * again.
         */
        gl.glStencilFunc(GL10.GL_EQUAL, 1, 0);

        /*
         * TODO STEP 34b: Change the stencil function to always keep (GL_KEEP)
         * the stencil buffer value in order to get overlaying shadows. If you
         * want to have physically correct shadows use GL_INCR for the z-pass
         * value. However, you won't see the nice cube shadow anymore as the
         * ceiling is taken into account.
         */
        gl.glStencilFunc(GL10.GL_KEEP, 1, 0);
        gl.glStencilOp(GL10.GL_REPLACE, GL10.GL_DECR, GL10.GL_INCR);

        gl.glPushMatrix();