ludic/packages/ludic.aim

ludic.aim

What the crosshair is on, and which thing the use key means. The crosshair is the exact middle of the screen and the projection is symmetric, so the ray through it is the camera's position along its forward - no unprojection. Each candidate is an upright cylinder widened by a fixed angular forgiveness, and the pick is the nearest one the ray enters that the ground does not hide. Uses ludic.base and nothing else.

import "ludic.aim"

The package keeps no list of things: the game offers every candidate each frame (aim_offer), keeps the object behind the id it gave, and draws the rim and the prompt.

The rule it keeps

The crosshair decides WHICH, the distance decides WHETHER (aim_use(kind)):

under the crosshair and in reach	AIM_USE_THIS - that, whatever else is nearer
under the crosshair and too far, within AIM_USE_MAX (10 m)	AIM_USE_NOTHING - and the prompt says why
nothing of that kind aimed at, or aimed past 10 m	AIM_USE_NEAREST - proximity is right again

Every reach is floored at AIM_REACH_MIN (3 m) by aim_reach_of(reach): a per-kind reach chosen against its model was never chosen against standing between two props and looking at one. Anything that asks "am I close enough to this" asks aim_reach_of.

The port

export port AimView {
  x, y, z, fx, fy, fz, fov,       # the camera (the ray)
  ground: fn(float, float) -> float,
  dry: fn(float, float) -> bool,  # land, for the probe's viewpoints
  body_x, body_z                  # distances and reach are the body's, not the camera's
}

Every member has a default: a camera 1.5 m up at the origin looking down -z over flat ground.

API

aim_begin(), aim_offer(kind, id, x, y0, y1, z, r, reach, far) -> bool	a frame's candidates: true when this one is now the pick (reach AIM_NEVER is never in reach)
aim_kind() (AIM_NONE for nothing), aim_id(), aim_dist(), aim_in_reach(), aim_t(), aim_off_centre()	the pick
aim_use(kind) -> AIM_USE_THIS / _NOTHING / _NEAREST, aim_reach_of(reach)	the use key
aim_ray_cyl(cx, y0, y1, cz, r), aim_slack_m(dist), aim_clear_to(x, y, z), aim_range(x, z), aim_miss(cx, cz, r)	the geometry, for a game's own probes
aim_probe_ground(px, pz, look) -> bool, aim_probe_seen(), aim_probe_blocked(), aim_probe_disagree()	from a point and a ring round it, lines at 60, 120 and 200 m on 36 bearings: the ground's own answer against aim_clear_to; look(x, y, z) puts the game's camera there

Tests

ludic test packages/ludic.aim

A camera over flat ground with a ridge: the ray against a cylinder, the forgiveness, near before far, the ground hiding a thing, the reach floor and the three answers for the use key, and the probe.