*****************************************************************************
                       Virtual Presence Engine API
*****************************************************************************

These functions are used by the main program to access the engine. The calls
should be done in the following order (VGA 320x200 assumed, 70 Hz timer):
	VPE_Init();
	VPE_Config(320,200);
	VPE_SetRate(INT_FIX(70));
	VPE_Start();
	while() {
		VPE_Update();
		VPE_Render();
	}
	VPE_Stop();
	VPE_Shut();
All the functions in the general API a part of the engine so they should not
be altered unless you know what you are doing. This is just layout of calls
to API, no hardware dependent calls.

=============================================================================
void VPE_Init(void);
-----------------------------------------------------------------------------
Description: 	Initialize the engine. The first VPE function to call.
Parameters: 	None
Return:		None
=============================================================================


=============================================================================
void VPE_Config(int ScrWidth, int ScrHeight);
-----------------------------------------------------------------------------
Description: 	Gives VPE info about the output device.
Parameters: 	ScrWidth  - width in pixels of the output device
		ScrHeight - height in pixels of the output device
Return:		None
=============================================================================


=============================================================================
void VPE_Shut(void);
-----------------------------------------------------------------------------
Description:	Shut down the engine
Parameters:	None
Return:		None
=============================================================================


=============================================================================
void VPE_Start(void);
-----------------------------------------------------------------------------
Description:	Prepare for the rendering process. Must be called before the
		actual rendering starts. VPE_Stop(), VPE_Start() pair should
		be used when the engine is to be paused.
Parameters:	None
Return:		None
=============================================================================


=============================================================================
void VPE_Stop(void);
-----------------------------------------------------------------------------
Description:	Stops the engine. For more info look at VPE_Start().
Parameters:	None
Return:		None
=============================================================================


=============================================================================
void VPE_Update(void);
-----------------------------------------------------------------------------
Description:	Updates all the zone info and prepares for rendering of the
		next frame. Usually used in pair with VPE_Render(). This
		function uses the time counter to calculate the frame-rate
		and adjust all movements. Must be called after VPE_Start().
Parameters:	None
Return:		None
=============================================================================


=============================================================================
void VPE_Render(void);
-----------------------------------------------------------------------------
Description:	Renders a complete frame to the output device. This function
		must be called only after VPE_Update().
Parameters:	None
Return:		None
=============================================================================


=============================================================================
void VPE_SetRate(FIXED TimerRate);
-----------------------------------------------------------------------------
Description:	Sets the rate of the external timer routine. Used for 
		real-time speed adjustment. This rate determines the max
		fps that can be achieved.
Parameters:	TimerRate - Ticks per seconds (Hz) of the timer counter
Return:		None
=============================================================================