flan/examples/models-box-collisions.flan
Joseph Ferano d7ceec448e Ten more raylib examples, and the three small structs 3D needed
Three shapes, two text, three textures, one models and one core, picked for
binding surface rather than for how they look.

shapes-basic-shapes brings in six draw families nothing had called — the
circle and rectangle gradients, the triangles, all three poly draws — and is
the first call in the corpus to pass two Colors or three Vector2s at once.
shapes-collision-area is get-collision-rec, the only binding that takes two
Rectangles and answers a third, on a frame path. shapes-following-eyes is the
raymath gap measured rather than worked around: every line of it is vector
arithmetic written without a vector library, the way the C writes it.

text-input-box drains get-char-pressed's queue, which no example had read,
and needed a MouseCursor defenum for set-mouse-cursor. text-writing-anim
replaces TextSubtext — unbindable, it answers a pointer into a rotating
static buffer — with (string (slice b 0 n)), which is the same operation
without the shared state.

textures-image-generation runs nine Gen* calls and the
gen/upload/unload-image path, all procedural, no file on disk.
textures-fog-of-war needed a TextureFilter defenum: the smooth fog edge is
entirely :bilinear on a 25x15 render texture, and it is also the first
draw-texture-pro with a negative source height. textures-mouse-painting is
the same render texture used as a document rather than as scratch, plus the
round trip back off the GPU — load-image-from-texture, image-flip-vertical,
export-image — which nothing had run.

models-box-collisions is the counterexample to "a models example is a binding
exercise": nothing in it is a Model, and one BoundingBox defstruct un-refuses
four functions. core-3d-picking is the only caller anywhere for Ray and
RayCollision, and picking is the inverse of the get-world-to-screen the
corpus already had.

Added to vendor/raylib: defstructs BoundingBox, Ray and RayCollision;
defenums MouseCursor and TextureFilter with their mapping lines in bindings;
hand-written declare-c for SetMouseCursor, SetTextureFilter, DrawCubeV,
DrawSphere, DrawSphereWires, DrawRay and GetScreenToWorldRay, each excluded
from the generated half on the rule bindings already states. generated.flan
regenerated against raylib 5.5: 272 declarations, 117 refused, every
defstruct, hand-written declare-c and mapped constant agreeing with the
header.
2026-09-13 14:42:49 +07:00

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;;;; raylib [models] example - box collisions
;;;;
;;;; examples/models/models_box_collisions.c. The previous lane's finding was
;;;; that the whole models category is refused by the importer for want of a
;;;; defstruct, and that a models example is therefore mostly a binding
;;;; exercise. That is true of the twenty that load a Model — but not of this
;;;; one, which is why it is here: nothing in it is a Model, a Mesh or a
;;;; Material. It is two cubes, a sphere and one aggregate the package did not
;;;; describe.
;;;;
;;;; That aggregate is BoundingBox, and it is two Vector3s and nothing else —
;;;; no owned pointer, no array, no lifetime. One `defstruct` in
;;;; vendor/raylib/raylib.flan un-refuses four raylib functions at once
;;;; (CheckCollisionBoxes, CheckCollisionBoxSphere, DrawBoundingBox and
;;;; GetRayCollisionBox), and that is the cheapest widening of the 3D surface
;;;; available anywhere in the tree. Ray and RayCollision went in beside it
;;;; for examples/core-3d-picking.flan and for the same reason.
;;;;
;;;; So the answer to "is a models example just a binding exercise" is: the
;;;; ones that need Model are, and this one is the counterexample. What
;;;; separates them is not the category, it is whether the struct owns memory.
;;;;
;;;; What it also exercises, and what needed hand-writing rather than
;;;; generating: draw-cube-v, draw-sphere and draw-sphere-wires. All three
;;;; were in the generated half already, and all three moved to the
;;;; hand-written one here on `bindings`'s own rule — they are inside a frame,
;;;; in an example that ships in examples/. draw-cube-v in particular was
;;;; named there as generated *because nothing called it*; something calls it
;;;; now.
;;;;
;;;; The collision maths is written twice in the C, once per test, building
;;;; the player's box inline both times. It is a function here for the reason
;;;; the eyes example gives: two copies of the same eight expressions cannot
;;;; be checked against each other by reading them.
(import rl "vendor:raylib")
(defconst screen-width 800)
(defconst screen-height 450)
(defvar camera rl/Camera3D)
(defvar player-position rl/Vector3)
(defvar player-size rl/Vector3)
(defvar player-color rl/Color)
(defvar enemy-box-pos rl/Vector3)
(defvar enemy-box-size rl/Vector3)
(defvar enemy-sphere-pos rl/Vector3)
(defconst enemy-sphere-size f32 1.5)
;; A box centred on `centre` with the given extents. raylib's BoundingBox is
;; min-corner/max-corner, not centre/size, and every collision call in the
;; family takes the corner form — so this is the conversion the C writes out
;; longhand at each of its two call sites.
(defn box-around [centre rl/Vector3 size rl/Vector3] rl/BoundingBox
(rl/BoundingBox
{.min (rl/Vector3 {.x (- (.x centre) (/ (.x size) 2.0))
.y (- (.y centre) (/ (.y size) 2.0))
.z (- (.z centre) (/ (.z size) 2.0))})
.max (rl/Vector3 {.x (+ (.x centre) (/ (.x size) 2.0))
.y (+ (.y centre) (/ (.y size) 2.0))
.z (+ (.z centre) (/ (.z size) 2.0))})}))
(defn main [] ()
(rl/init-window screen-width screen-height
"raylib [models] example - box collisions")
(defer (rl/close-window))
;; The C writes this camera as a brace initialiser with a trailing 0 for the
;; projection, which is CAMERA_PERSPECTIVE. Named here, because the defenum
;; exists precisely so that the 0 does not have to be remembered.
(set camera (rl/Camera3D {.position (rl/Vector3 {.x 0.0 .y 10.0 .z 10.0})
.target (rl/Vector3 {.x 0.0 .y 0.0 .z 0.0})
.up (rl/Vector3 {.x 0.0 .y 1.0 .z 0.0})
.fovy 45.0
.projection :perspective}))
(set player-position (rl/Vector3 {.x 0.0 .y 1.0 .z 2.0}))
(set player-size (rl/Vector3 {.x 1.0 .y 2.0 .z 1.0}))
(set player-color rl/green)
(set enemy-box-pos (rl/Vector3 {.x -4.0 .y 1.0 .z 0.0}))
(set enemy-box-size (rl/Vector3 {.x 2.0 .y 2.0 .z 2.0}))
(set enemy-sphere-pos (rl/Vector3 {.x 4.0 .y 0.0 .z 0.0}))
(rl/set-target-fps 60)
(until (rl/window-should-close?)
;; Update. The arrow keys move on the XZ plane, and the C's else-if chain
;; means only one direction applies per frame — diagonal movement is not
;; possible, deliberately.
(cond
(rl/key-down? :right) (set (.x player-position) (+ (.x player-position) 0.2))
(rl/key-down? :left) (set (.x player-position) (- (.x player-position) 0.2))
(rl/key-down? :down) (set (.z player-position) (+ (.z player-position) 0.2))
(rl/key-down? :up) (set (.z player-position) (- (.z player-position) 0.2)))
(let [player-box (box-around player-position player-size)
hit (or (rl/check-collision-boxes player-box
(box-around enemy-box-pos enemy-box-size))
(rl/check-collision-box-sphere player-box enemy-sphere-pos
enemy-sphere-size))]
(set player-color (if hit rl/red rl/green)))
;; Draw
(rl/begin-drawing)
(rl/clear-background rl/raywhite)
(rl/begin-mode-3d camera)
(rl/draw-cube enemy-box-pos (.x enemy-box-size) (.y enemy-box-size)
(.z enemy-box-size) rl/gray)
(rl/draw-cube-wires enemy-box-pos (.x enemy-box-size) (.y enemy-box-size)
(.z enemy-box-size) rl/darkgray)
;; draw-sphere is draw-sphere-ex at 16 rings and 16 slices; the wires form
;; takes them because the tessellation is only visible in the wireframe.
(rl/draw-sphere enemy-sphere-pos enemy-sphere-size rl/gray)
(rl/draw-sphere-wires enemy-sphere-pos enemy-sphere-size 16 16 rl/darkgray)
(rl/draw-cube-v player-position player-size player-color)
(rl/draw-grid 10 1.0)
(rl/end-mode-3d)
(rl/draw-text "Move player with arrow keys to collide" 220 40 20 rl/gray)
(rl/draw-fps 10 10)
(rl/end-drawing)))