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Implement trapezoid texturing

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This commit is contained in:
Jeremy Penner 2023-12-24 16:56:21 -05:00
parent 7148e21cce
commit 6027fdf387
1 changed files with 45 additions and 16 deletions
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61
index.js
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@ -188,6 +188,20 @@ celDecoder.box = (data, cel) => {
cel.bitmap = bitmap
}
const horizontalLine = (bitmap, xa, xb, y, patternByte) => {
const xStart = xa - (xa % 4)
const xEnd = (xb + (3 - (xb % 4))) - 3
for (let x = xStart + 4; x < xEnd; x += 4) {
drawByte(bitmap, x, y, patternByte)
}
const startBit = ((xa - xStart) * 2)
const startByte = (0xff >> startBit) & patternByte
drawByte(bitmap, xStart, y, startByte)
const endBit = (((xEnd + 3) - xb) * 2)
const endByte = (0xff << endBit) & patternByte
drawByte(bitmap, xEnd, y, endByte)
}
celDecoder.trap = (data, cel) => {
let border = false
// trap.m:21 - high-bit set means "draw a border"
@ -208,7 +222,22 @@ celDecoder.trap = (data, cel) => {
} else {
// shape_pattern is 0xff, and the pattern is a bitmap that follows
// the trapezoid definition
throw Error("TODO: Implement inline trapezoid patterns")
// dline.m:103 - first two bytes are bitmasks used for efficiently calculating
// offsets into the texture. This means that the dimensions will be a power of
// two, and we can get the width and height simply by adding one to the mask.
const texW = data.getUint8(11) + 1
const texH = data.getUint8(12) + 1
cel.texture = emptyBitmap(texW, texH)
let i = 13
// dline.m:111 - the y position into the texture is calculated by
// ANDing y1 with the height mask; thus, unlike prop bitmaps, we decode
// from the top down
for (let y = 0; y < texH; y ++) {
for (let x = 0; x < texW; x ++) {
drawByte(cel.texture, x * 4, y, data.getUint8(i))
i ++
}
}
}
cel.x1a = data.getUint8(7)
cel.x1b = data.getUint8(8)
@ -248,25 +277,25 @@ celDecoder.trap = (data, cel) => {
let xa = cel.x1a
let xb = cel.x1b
for (let y = 0; y < cel.height; y ++) {
let patternByte = cel.pattern
const line = cel.bitmap[y]
if (border && (y == 0 || y == (cel.height - 1))) {
// top and bottom border line
patternByte = 0xaa
horizontalLine(cel.bitmap, xa, xb, y, 0xaa, true)
} else {
if (cel.texture) {
const texLine = cel.texture[y % cel.texture.length]
for (let x = xa; x <= xb; x ++) {
line[x] = texLine[x % texLine.length]
}
// draw a horizontal line from xa,y to xb,y
const xStart = xa - (xa % 4)
const xEnd = (xb + (3 - (xb % 4))) - 3
for (let x = xStart + 4; x < xEnd; x += 4) {
drawByte(cel.bitmap, x, y, patternByte)
} else {
horizontalLine(cel.bitmap, xa, xb, y, cel.pattern, border)
}
}
if (border) {
line[xa] = 2
line[xb] = 2
}
const startBit = ((xa - xStart) * 2)
const startByte = border ? (0xff >> (startBit + 2)) & patternByte | (0x80 >> startBit)
: (0xff >> startBit) & patternByte
drawByte(cel.bitmap, xStart, y, startByte)
const endBit = (((xEnd + 3) - xb) * 2)
const endByte = border ? (0xff << (endBit + 2)) & patternByte | (2 << endBit)
: (0xff << endBit) & patternByte
drawByte(cel.bitmap, xEnd, y, endByte)
// cycle1: move xa
do {