Pro OpenGL ES for iOS

CHAPTER 7: Well-Rendered Miscellany (^233)
m_SpinX+=.4f;
m_SpinY+=.6f;
m_SpinZ+=.9f;
return;
}
So, what’s going on here? Well, sit a spell, and I’ll tell you:
„ Lines 1f are used to turn the light on and off so as to take before and
after comparisons.
„ Line 2 just generates the bounce factor. Since we need it twice, I
pulled it out of the call to glTranslate() where it used to be.
„ The light’s position is updated at line 3 and is detailed later.
„ In line 4, the lighting is turned off briefly because it can affect the way
the shadows are rendered.
„ Line 5 translates the scene to mWorldY and mWorldZ coordinates.
„ The platform, or stage, is drawn in line 6.
„ Lines 7ff toggle the light on and off every few seconds to show the
scene with and without the shadow.
„ In line 8, the drawLight() routine (Listing 7-13) is called to place a little
floating ball in orbit around our scene.
„ We need to disable the depth test when actually drawing the shadow,
in line 9, otherwise, there will be all sorts of z contention that generates
cool but useless flickering.
„ Line 10 calls the routine to generate the shadow’s matrix (detailed
later), followed by line 11, which actually draws the shadow.
„ Finally, we can start managing the occluder in line 12, the thing that
actually causes the shadow to be thrown.
„ Line 13 is used to aim our eye point down to center the scene since
we are floating up above it.
„ N o w w e g e t t o t h e b o u n c y p a r t -----nothing really new in line 14.
„ Lines 15ff add the extra spins. Note that the shadow generator also
has the identical rotational code.
„ Line 16 safely turns on the depth testing again, after which we can
draw the two triangle fans as well.
„ Lines 17ff handles some of the animation parameters, and then the
buffer is updated to the screen.