ludic/packages/ludic.lab/README.md

ludic.lab

The visual lab: one model or one mechanic on a plate, photographed from fixed cameras. A lab scene is a minimal, isolated, reproducible piece of a game - never the whole world. The plate is a flat, lit disc 40 m across with a line every metre, a small sky of its own with the sun 40 degrees up (one fixed hour), and a clock of frames: 60 a second, whatever the machine. Nothing else is loaded - no terrain, no grass, no water (r3d_plate_mode in ludic.render3d) - so a scene starts in about a second and takes about 120 MB resident (420 MB peak footprint with the GPU driver's share) where a lab on a whole valley took 7.8 GB.

module ludic_lab uses ludic_render3d, ludic_base.

A lab program

import "ludic.lab"
program Lab {
  numbers float
  function probe_setup() -> void {
    lab_model(lab_plate_dir(), "probe.gltf", "probe", 0.0, 0.0, 0.5)
    lab_shot_at("front", 0.0, 0.7, 0.0, 4.0, 0.0, 12.0)
    lab_shot_at("above", 0.0, 0.5, 0.0, 7.0, 30.0, 55.0)
  }
  def LabScenes probe { setup: fn probe_setup }
  handler Boot phase Start { lab_boot() }
  handler Look phase Input { lab_input() }
  handler Draw phase Render { lab_render() }
}

example/plate.ludic is this program. Scenes are an open registry, so a game - or a package showing its own models - adds them from its own module with def LabScenes <name> { ... }:

field
setup: fn()	build what the scene shows and name its cameras
tick: fn(float)	move it, by the lab's fixed step (1/60 s)
draw: fn()	draw what is not an actor or a scatter layer (actors and layers are drawn already)

R3D_SCENE=<name> picks the scene (the first one added otherwise); an unknown name lists them.

Running it

• Headless (ludic build ... --headless): every shot is held lab_settle frames (45), written to build/lab/<scene>/<shot>.png, and after the last the program quits. The headless loop reads a line of stdin a frame: yes '' | head -n 20000 | R3D_SCENE=probe ./lab.
• In a window: N and P step through the shots.
• tools/lab/run.sh <lab.ludic> <scene> ... (in the toolchain's checkout) builds the program, runs each scene and makes build/lab/<scene>/sheet.png, a contact sheet (tools/lab/sheet.py).

API

lab_boot(), lab_input(), lab_render()	the program's Start, Input and Render handlers
lab_shot(name, x, y, z, yaw_deg, pitch_deg)	a camera at a point, looking along yaw and pitch (degrees)
lab_shot_at(name, tx, ty, tz, dist, from_deg, up_deg)	a camera dist metres from a point, from a bearing (0 = from +z), up_deg above it, looking at it
lab_shot_count()	the cameras named so far
lab_model(dir, file, node, x, z, yaw) -> Actor, lab_stand(a, x, z, yaw), lab_ground_y(x, z)	a glTF node stood on the plate; the plate is flat at y = 0
lab_plate_dir()	the package's plate/: the disc, its sky and the probe model
lab_settle(frames), lab_font(dir), lab_title(s), lab_note(s)	how long a shot settles; the overlay font for captions (none by default); the window's title; a line under the caption
lab_scene(), lab_frame(), lab_time()	the scene, and the lab's clock
lab_ppm_to_png(ppm, png)	a frame as a PNG (stored, not compressed)

The plate's files

plate/ is built by tools/lab/plate_build.py in the toolchain's checkout and is deterministic: plate.gltf (the disc), probe.gltf (a box with a ball on it, for looking at the light), and sky.hdr (512 x 256, the sun at 40 degrees). Change the script and run it again; never edit them.

Not here yet

• A heightfield patch for a scene that needs a slope: the plate is flat.