2 Commits

Author	SHA1	Message	Date
Andrew Kesterson	9056ff06d6	Add collision shapes, on the character and overridable per actor ... A shape is a convex volume positioned relative to an actor's origin. It lives on akgl_Character, so every goblin sharing a character shares one shape definition the way they already share speeds and the state-to-sprite map, and an actor may override it with akgl_Actor::shape_override. The flag is not redundant with an empty shape. "This actor deliberately has no collider" and "this actor has not been given one yet" are different states, and without somewhere to record the difference akgl_actor_set_character cannot tell whether it is allowed to overwrite what it finds. include/akgl/collision.h is a leaf: it names actors and tilemaps as incomplete struct pointers rather than including their headers, because both of those need akgl_CollisionShape by value and a cycle forms otherwise. The `headers` suite compiles it as the first include of a translation unit, so that property is enforced rather than merely intended -- which is why the tilemap types got struct tags two commits ago. The masks are asymmetric and the defaults are the load-bearing part: layermask ACTOR, collidemask STATIC. An actor given a shape and nothing else collides with map geometry and with no other actor. "Everything with a hitbox shoves everything else" would be a surprising default for a town full of scenery and a painful one to discover after the fact; opting in to actor-versus-actor is one bit, opting out of it would have been a hunt through every NPC a game spawns. Every shape gets a z depth, because the narrowphase behind this is three dimensional and answers with the *minimum* separating translation. A thin extrusion makes z the cheapest axis, and an actor pushed along z goes nowhere a player can see while remaining inside the floor -- a collision system reporting success while doing nothing. The ratio of 2 is the smallest for which the z overlap of any two shapes the setters build provably exceeds any planar penetration they can reach. The test for that asserts the inequality across a spread of sizes rather than asserting the constant is 2, so a change to the constant fails here rather than in a game. Two things about that test are worth recording, because the first version had both: - It could not fail. TEST_ASSERT expands to FAIL_BREAK, which reports by `break`ing, and the assertion was inside a nested `for` -- so the break left the loop rather than the ATTEMPT block and the failure evaporated. This is the hazard AGENTS.md documents for CATCH; it applies to the whole family. Verified by setting the ratio to 0.5 and watching the suite still pass, then fixing it and watching it report the 512x512 case by name. - tests/collision_arena.c had the same bug in a loop added in the previous commit, and it is fixed here too. Co-Authored-By: Claude Code <noreply@anthropic.com> Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-08-01 23:48:05 -04:00
Andrew Kesterson	46232a5ad1	Give libccd a static arena so libakgl still allocates nothing ... libakgl does not call malloc at runtime. That is stated in seven places in the manual and is AGENTS.md's second standing rule, and every object comes from a fixed array in akgl/heap.h. libccd's EPA path does not know that: it builds its expanding polytope out of realloc and free, and ccdGJKPenetration documents a -2 return for when that fails. The alternative was to compile only the three files MPR needs and leave EPA out of the build. That works and it puts a copy of somebody else's source list in this repository, where it rots silently on the next submodule bump. This instead compiles all of libccd and points its allocator at a bump allocator over static BSS, which keeps the promise literally true -- and keeps EPA available rather than amputated, for the day a precise contact manifold is worth having. The arena is reset at the top of each query rather than freed block by block, so the lifetime is one narrowphase call, `free` is a no-op, and allocation is a pointer bump. Exhaustion returns NULL, which libccd already handles by unwinding to -2, which becomes AKGL_ERR_COLLISION naming the high-water mark -- a loud failure with a number in it rather than a silently missed collision, which would be a floor an actor falls through reported as success. One GJK/EPA box pair costs 7,264 bytes, measured and printed by the suite. The 64 KB ceiling is that with about nine times headroom, and the high-water mark is reported so the next reader can re-derive it rather than trust this line. The redirect lives in src/ccd_arena_shim.h, injected with -include, and not in CMake's COMPILE_DEFINITIONS. It was in COMPILE_DEFINITIONS first, and that is a mistake worth recording: CMake cannot carry a function-like macro through a -D, so it dropped __CCD_ALLOC_MEMORY without a diagnostic. libccd went on calling the C library's realloc while the shim's `free` quietly discarded the results -- strictly worse than doing nothing, and invisible, because it leaks rather than crashes. What caught it was insisting the test prove the wiring rather than the outcome. The first version asserted the arena balanced back to zero after a query, which turned out to be the wrong assertion for a different reason -- free is a no-op by design, so it cannot balance -- but a test that had merely checked "two boxes collide" would have passed throughout, against an allocator nothing was using. The suite now asserts what is actually provable: that a query allocates from the arena at all, and that the process survives, since glibc aborts when the real free(3) is handed a pointer it never issued. Also here: AKGL_ERR_COLLISION, with the name registered -- tests/error.c asserts the band and the names agree, and it caught the missing one immediately. -fvisibility=hidden and CCD_STATIC_DEFINE keep every ccd* symbol out of libakgl.so's dynamic table, which `nm -D` confirms is empty; AGENTS.md records a shipped defect where an exported `renderer` was preempted by a same-named symbol elsewhere, and a game linking a system libccd would hit exactly that. Co-Authored-By: Claude Code <noreply@anthropic.com> Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-08-01 23:29:37 -04:00