Path: utzoo!attcan!uunet!cbmvax!ken
From: ken@cbmvax.commodore.com (Ken Farinsky - CATS)
Newsgroups: comp.sys.amiga.tech
Subject: Re: ===> Need help with hardware sprites <===
Message-ID: <13892@cbmvax.commodore.com>
Date: 20 Aug 90 14:23:25 GMT
References: <19919.26cec9ee@merrimack.edu>
Reply-To: ken@cbmvax (Ken Farinsky - CATS)
Organization: Commodore, West Chester, PA
Lines: 73

In article <19919.26cec9ee@merrimack.edu> greenwoode@merrimack.edu (Ed Greenwood) writes:
>     Using Lattice C (v. 5.04), I have been unable to make more than 
>one hardware sprite appear on the screen at the same time.  Whenever I 
>place a sprite on the screen, all other sprites will immediately 
>disappear...

I would suggest reading the beginning of the chapter "Graphics:  Sprites,
Bobs and Animation", from the ROM Kernel Manual:  Libraries and Devices.

For each sprite that you use, you have to "get" another one from the
system.  For instance, if you want to use sprites 2 and 3 (note that
sprite 0 is the intuition pointer and sprite 1 can be paired with it,
avoid these sprites if possible...) you would do something like:

	struct SimpleSprite sprite2,sprite3;
	extern UWORD chip sprite_data2,sprite_data3;

	if (-1 == (sprite_number2 = GetSprite(&sprite2,2))
		; /* error, could not get sprite */
	else
		{
		/* here we can use sprite2 */
		if (-1 == (sprite_number3 = GetSprite(&sprite3,3))
			; /* error, could not get sprite */
		else
			{
			/* here we can use sprite3 */
			ChangeSprite(NULL,&sprite2,sprite_data2);
			ChangeSprite(NULL,&sprite3,sprite_data3);

			/* do more stuff here */
			rest_of_program(&sprite2,&sprite3);

			/* after you are done with the sprites,
			** free them.
			*/
			FreeSprite(sprite_number3);
			}
		FreeSprite(sprite_number2);
		}

If you "re-use" a sprite, say sprite 2, and load new data into it, then
the old image will go away when the new one appears.

>...I know the "-ad" option must be used when compiling a 
>program that uses sprites, but is there anything else that must be done? 

You do NOT need to use the -ad flag when using sprites, you simply must
insure that the sprite image data is in chip memory.  you can do this
with the following construct:

	UWORD chip sprite_data[] =
		{
		0,0, /* position control */
		0xffff, 0xffff, /* image data goes in here */
		0,0, /* after image data must have 0,0 */
		};

This is the only part of a sprite that has to go into chip memory.
You can use the chip or __chip keywords to tell lattice that the data
is to be placed into chip memory.  Once you have access to the sprite,
install the data with a call to ChangeSprite().

>My knowledge of sprite graphics has come from the book, INSIDE THE AMIGA
>WITH C.  Are the sprite examples in this correct?

Don't know.

-- 
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Ken Farinsky - CATS - (215) 431-9421 - Commodore Business Machines
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