SPRITE BANK b [,o, p, n]

which lets NextBASIC know in which bank b, are the sprite patterns located. Optionally you can define a number n of sprite patterns beginning with pattern p, located at bank offset o.

In the case above, we already know the bank and we do not need any more identification factors so let's tell NextBASIC where we put the sprites by adding:

90 SPRITE BANK a

All is now left to do, is show our sprite. For this we need two commands. First we need to enable sprites with:

SPRITE PRINT n

where n can be 0 or 1 enables sprites (1) or disables (0) them. This is actually showing the sprites, but freshly initialised sprites contain no image (pattern), nor display information. We need to assign at least one pattern to one sprite "slot" and tell the Sprite System that the particular sprite "slot" is visible for that to happen.

In our example so far (that will soon change), we only have one pattern so that's not particularly difficult. We also need to place the sprite somewhere on the screen AND possibly rotate it. If you go back to our sprite design, you'll see it's a spaceship facing upwards; we may need to make it turn to the left or right. All of the above (and one more thing) can be achieved with a single command:

SPRITE s, x, y , p, f,rf,mx,my

which in one go: sets sprite number s, to pattern number p, then update its position to location x, y with flags f, relative flags rf, x-scaling mx and y-scaling my.

If the sprite id s is negative, this sprite is a relative sprite, and its position is relative to the previous anchor sprite (defined with a positive sprite id). See later for more information on relative sprites. Flags is a bitmask (we've covered bitmasks before in Chapter 6 so that should be easy already) that sets the following:

Bit 0 is the visibility flag. 0 is for invisible and 1 is for visible

Bit 1 is the rotate flag. 0 for standard, 1 for a 90° clockwise rotation

Bit 2 is the Y–mirror flag. 0 is for non-mirrored vertically while 1 is for mirrored

Bit 3 is the X-mirror flag. Again it's 0 for non-mirrored horizontally while 1 is for mirrored

while

Bits 4 through 7 define a 4-bit palette offset (or 0).

The Relative Flags rf is also a bitmask that sets the following:

The relative-flags parameter, rf, is also a bitmask:

Bit 0: type: 0=composite, 1=unified [only valid for anchor sprites]

Bit 1: pattern is relative to the anchor [only valid for relative sprites]

Bit 2: palette offset is relative to the anchor [only valid for relative sprites]

The scaling parameters mx and my are:

0=1x (no scaling)

1=2x

2=4x

3=8x

Any parameters in the SPRITE command can be omitted, and its value will be left unchanged from the last time it was explicitly specified. It's a good idea again to use the BIN function to easily specify the flag parameters in a more convenient way.

We'll explain in a little bit the part about the palette offset but for now, let's add a non-mirrored, non-rotated sprite 0 with the pattern 0 we defined, put it at approximately the centre