121 lines
4.3 KiB
JavaScript
121 lines
4.3 KiB
JavaScript
/**
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* Basic sprite compiler
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*
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* GTE has some specific needs that makes existing tools (like MrSprite) inappropriate. GTE
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* sprites need to reference some internal data structures and have slightly different code
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* in order to handle clipping to the playfield bounds.
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*
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* The core sprite drawing approach is the same (set up Bank 1 direct page and stack), but
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* the setup and dispatch are a bit different.
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*
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* A Note on Clipping
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*
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* GTE supports two clipping buffers for sprites to use. The first one is a static buffer
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* that is aligned with the playfield and is used to clip the sprite when crossing the
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* left and right boundaries, but since it's a static image, mask data can be put anywhere
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* that the sprites should not show through, so irregular borders and sprite punch-outs
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* on the playfield are possible.
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*
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* The second buffer matches the current tiles in the playfield and can be used as a
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* dynamic mask of the playfield. Since the sprite code itself must use this data,
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* different variations of the same sprite can be created to stand in "front" and "behind"
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* different screen elements.
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*
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* The sprite requires the X and Y registers for this. The most general code that
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* should be used for each sprite word is this:
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*
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* Example: DATA = $5670, MASK = $000F, screen_mask = $FF00, field_mask = $F0FF
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* lda DP ; A = $1234
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* eor #DATA ; A = $4444
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* and #~MASK ; A = $4440
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* and screen_mask,y ; A = $4400
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* and >field_mask,x ; A = $4000
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* eor DP ; A = $5234 <-- Only the high nibble is set to the sprite data
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* sta DP
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*
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* It is not *required* that sprites use this approach, any compiled sprites code can be used,
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* so if a sprite does not need to be masked, than any of the fast sprite approaches can be
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* used.
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*
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* For clipping vertically, we pass in the starting and finishing lines in a register and
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* a sprite record is set up to allow the sprite to be entered in the middle and exited
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* before the last line of the sprite.
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*/
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const { readPNG, pngToIIgsBuff } = require('./png2iigs');
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const process = require('process');
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main(process.argv.slice(2)).then(
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() => process.exit(0),
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(e) => {
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console.error(e);
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process.exit(1);
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}
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);
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async function main(argv) {
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const png = await readPNG(argv[0]);
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const buff = pngToIIgsBuff(png);
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const options = {
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staticClip: true,
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label: 'Sprite001'
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};
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startIndex = getArg(argv, '--start-index', x => parseInt(x, 10), 0);
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asTileData = getArg(argv, '--as-tile-data', null, 0);
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maxTiles = getArg(argv, '--max-tiles', x => parseInt(x, 10), 64);
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}
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function getArg(argv, arg, fn, defaultValue) {
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for (let i = 0; i < argv.length; i += 1) {
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if (argv[i] === arg) {
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if (fn) {
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return fn(argv[i+1]);
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}
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return true; // Return true if the argument was found
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}
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}
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return defaultValue;
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}
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function buildMerlinCodeForSprite(sprite, options) {
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const { label, staticClip } = options;
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const rtnOpCode = options.longReturn ? 'rtl' : 'rts';
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const sb = new StringBuilder();
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sb.appendLine(`${label} ENT`);
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sb.appendLine(` cpx #${sprite.height * 2}`);
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sb.appendLine(` bcc *+3`);
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sb.appendLine(` ${rtnOpCode}`);
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sb.appendLine(` sei`);
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sb.appendLine(` tcs`);
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sb.appendLine(` jmp (${label}_jtbl,x)`);
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sb.appendLine(`${label}_jtbl`);
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for (let line = 0; line < sprite.rows.length; line += 1) {
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lda DP ; A = $1234
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* eor #DATA ; A = $4444
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* and #~MASK ; A = $4440
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* and screen_mask,y ; A = $4400
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* and >field_mask,x ; A = $4000
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* eor DP ; A = $5234 <-- Only the high nibble is set to the sprite data
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* sta DP
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sb.appendLine(` dw ${label}_${line}`);
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}
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// Implement each line to draw the sprite data
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//
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// label_XX tdc
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// clc
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// adc #160*line
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// tcd
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// main_XX lda 00
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// and #
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// ora #
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//
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for (let line = 0; line < sprite.rows.length; line += 1) {
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}
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return sb.toString();
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} |