Entry 248

The marks' face word, and the flight quads' screen test

2026-10-231h 1mrender

Filescrates/rugrats/src/world/flights.rscrates/rugrats/src/world/game/things.rsmod.rsdocs/engine/gameplay.mdobjectives.md

Two of the long-open drawing items are decoded. A mark's face word turns out to set its draw depth, and the flight quads have a screen test. The port also now draws a mark grey 128 in a room of flag 8, and culls flight quads as the original's.

The face word (0x800243c4 through 0x80023c2c, 0x800233f4, 0x800221cc; gameplay.md, the flights' marks):

• Top two bits: the primitive (3 a quad).
• 0x800000: textured.
• 0x2000000 and 0x1000000: the POLY's semi and raw bits (code 0x2c for the FT4).
• 0x600000: the page's blend.
• 0x200: a screen test (0x800239e8, 0x80023a8c).
• 0x400: a face with a corner clipped is skipped (vertex +6 & 48).
• 0x800: a face wholly off one side is skipped.
• 32, 64, 128 and 256: the flag word, the corners, the texture and the colour are kept for the next face.
• 0x7000: the ordering table's depth (0x800221cc): 0 the first corner's, 0x1000 the last's, 0x2000 the corners' mean, 0x3000 the nearest, 0x4000 the farthest.
• 0x8000: that depth 64 nearer.

The marks (0x8008652c):

• Which word. It is chosen by the normal met, not by the tile's +4 as gameplay.md had it. A wall (the normal's y 0) gets 0xc080be00: in at its nearest corner pulled 64 forward. A floor or ceiling gets 0xc0802e00: in at the mean. +0x89 adds 0x2000000.
• The draw (0x8008e508) is one quad, or, with the record's bit 0x8000000, a 3 x 3 grid of four (the word | 416).
• The colour. The record's colour, but 128 when the room of the mark (its +0x0a, the flight's launch room +0x38) has flag 8 (room +0x0c).
• The port has a depth buffer and already passes a decal's equal depth and biases it forward. It now keeps each flight's launch room (Flight::room, Flown::room) and lays a mark grey 128 when that room has flag 8.

The flight quads' screen test (0x8008a954), worklog 114's and 239's open item:

• It comes after the depth test (0 to 65535 ahead).
• The corners (-w, -h), (w, -h) and (-w, h) are turned by the roll (rcos, -rsin; rsin, rcos), x scaled as the view (0x8001e0f4), and projected (RTPT).
• The quad is drawn only when one of them is on the screen within 167 / 128 of its extents: 0x800c4a00's 512 and 240, so |sx| < 668 and |sy| < 313.
• The port's Flights::draw takes that test from the game's render eye.
• The four-quad split (face 0x8000000: the centre and the edges' midpoints by three more RTPTs) only changes how the texture lies; the port draws one quad.

Checked: every test file, and the hle suite.

No room of any level has flag 8 once its LP kind 6 records are read (every level opened in the port, room +0x0c), so in the game a mark always takes its own colour.