Entry 130

"The field's weather: rain, snow, fireflies and the rest of WORLD::Draw"

2026-09-25worldrendertest

Filescrates/piney-world/src/field_ambient.rscrates/piney-world/src/field_firefly.rscrates/piney-world/src/firefly.rscrates/piney-world/src/field_area.rscrates/piney-world/src/field_world.rscrates/piney-world/src/lib.rscrates/piney-world/examples/ambient_probe.rscrates/piney-data/src/anim.rscrates/piney-data/src/field/render.rscrates/piney-data/src/field/mod.rscrates/piney-game/src/fx.rscrates/piney-game/src/fx/ambient.rscrates/piney-game/src/area.rscrates/piney-game/src/main.rstools/test_field_ambient_rs.pydocs/engine/field.mddocs/engine/field-walk.md

The port's fields drew their ground, objects, lake and sky, and nothing else WORLD::Draw does: no rain, no snow, no fireflies at night, no steam over type 0's lava, none of the servers' travellers crossing the sky. This entry ports all of it, checked against the game frame by frame, and draws it in the field.

What the game draws

WORLD::Init and Generate make the pieces and Draw / DrawEffect step and draw them every frame, all from fieldrand except type 7's fires, which turn with ccRand. field.md, "Weather and ambient pictures", has the whole listing. In short:

• Snow. 100 or 200 SNOWs falling round WORLD_MAN's centre (types 5 and 6); type 0's 16 embers rise from the ground.
• Rain. 50 drops with their splashes. In a storm there are also bolts on the horizon, and a flash of the screen with thunder every 900-1,499 frames.
• Smoke. Type 7's fires smoke on even frames. Type 0's vents steam in bursts of eight.
• The 2D smoke. Types 2, 3, 5 and 6 drift big translucent puffs of TEX_sfsmo1 across the screen for a few seconds now and then.
• The heat haze. Types 0-3 draw a model ahead of the player whose texture is the picture drawn so far, so the horizon shimmers.
• Fireflies. Five FIREFLYs at night, or glyph trails when hacked. Type 9 has fifteen FIREFLY2s instead.
• TOBJ. One field in seven gets the server's traveller.
• BIRD. A hawk over the dungeon entrance by day in type 10.
• The lens flare.

The game's slips

Each of these is kept, because the random draws depend on them.

• Rain placement. DrawRain sets WORLD +0x1c where it meant the drop's own "placed" flag, so all 50 drops are placed again every frame (100 draws).
• Snow height. A flake's height asks GetHeight(x, y != -500).
• Snow at Init. The flakes made in Init ask for heights before the map exists, which is the heap's garbage in the game (zeros in eemu and here). They also fall round a centre GO never set.
• BIRD's far test. It adds d.y twice where it meant d.y squared.
• The 2D smoke's transparency. It is an int, so the fade out takes a single frame.
• The bolt's offset. A negative offset is converted as unsigned.
• Type 9's FIREFLY2. It takes its height at the offset instead of the place.

The port

• piney_world::field_ambient. Makes the pieces with the field. Each frame it hands back the pictures as a list of Ops in the game's order: sprites, smoke puffs, masks, models, sounds and the flash.
• field_firefly. FIREFLY (its splines are FRAC2's natural spline).
• firefly. Gains type 9's FIREFLY2 path.
• FieldArea. Carries fieldrand on from Generate, keeps the drawing's function statics across fields, and draws the haze, TOBJ, BIRD and the 2D smoke.
• AreaFx. A new FieldFx::field_ambient draws the ccEffs, each made once as its Init left it. The puffs queue for effSmoke, and the sounds and flash go out with the area's events.

Three things came to light while wiring it up.

• The haze's model. OBJ_sfzair00 is an ExtObj. Its model is found through the target, and the posed object is picked by that model, not by name.
• TOBJ's "fog" is a shadow. The two ccDrawEnv fields TOBJ sets are read by ccShadowModel::Draw (main 0x001412b0) as the shadow's length and transparency. The fog lives elsewhere (+0xb8..+0xd8, SetFog).
• Where the fires come from. They are set by SetSpecialObj in EntryGimmick, which the port's fields don't have yet. The runtime finds them as the field is made: each chip object's OBJ_roc1fire and OBJ_roc3fire node in its animation, plus the object's wp. The nodes are matched by name, because the file holds two objects of each name. The smoke rises from the braziers' tops in the shot.

piney-game --mode field:14/TYPE,ROW[,HACK[,SEED]] puts another field's type, weather row, hack flag and seed into story area 14's WORLD_MAN, for looking at any weather.

Checked

• tools/test_field_ambient_rs.py (new). It runs the game's Init, Generate and Draw in eemu against the ambient_probe example, over every field type and background row, hacked and not, on a random server and seed, with the player and camera walking. It compares fieldrand's counts, everything Init and Generate made, and every frame's pictures in order along with the fieldrand and ccRand counts. It ran 124 cases of 1,000 frames with 0 mismatches. Every snow, rain, storm, flare, firefly and ember sprite showed up, as did the masks, puffs, sounds, flash, bird, haze and TOBJ.
• Shots. Rain, a storm, heavy and light snow, night with fireflies, type 9 at night, the bird, type 7's fires, type 0's steam and haze, hacked, and the 2D smoke.
• The workspace's tests, clippy, fmt, and test_evarea_rs for the shared FIREFLY2 all pass.