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#include "physics.hpp"
#include "components.hpp"
#include "ecs.hpp"
#include "game-settings.hpp"
#include "pk.h"
#include <LinearMath/btAlignedAllocator.h>
#include <btBulletDynamicsCommon.h>
#include <BulletCollision/BroadphaseCollision/btOverlappingPairCache.h>
#include <BulletDynamics/Dynamics/btRigidBody.h>
TypeSafeInt_B(PhysicsCollision);
struct pk_membucket *MemBkt_Bullet = nullptr;
btDiscreteDynamicsWorld *BtDynamicsWorld = nullptr;
struct AllocedData {
void *data;
std::size_t size;
};
pk_arr_t<AllocedData> bulletAllocs{};
btHashedOverlappingPairCache *overlappingPairCache = nullptr;
btDefaultCollisionConfiguration *btConfiguration = nullptr;
btCollisionDispatcher *btDispatcher = nullptr;
btDbvtBroadphase *btBroadphase = nullptr;
btSequentialImpulseConstraintSolver *btSolver = nullptr;
struct EntityCollision {
CompInstance *a, *b;
};
pk_arr_t<EntityCollision> collisionsThisTick{};
void *pke_btAlignedAllocFunc(size_t size, int alignment) {
void *ptr = pk_new_bkt(size, alignment, MemBkt_Bullet);
pk_arr_append_t(&bulletAllocs, {ptr, size});
return ptr;
}
void pke_btAlignedFreeFunc(void *memBlock) {
int64_t index = -1;
uint32_t i, count;
count = bulletAllocs.next;
for (i = 0; i < count; ++i) {
if (bulletAllocs[i].data == memBlock) {
index = i;
break;
}
}
assert(index != -1);
pk_delete_bkt(memBlock, bulletAllocs[index].size, MemBkt_Bullet);
pk_arr_remove_at(&bulletAllocs, index);
}
void *pke_btAllocFunc(size_t size) {
// 2025-06-05 JCB
// I have no idea what minimum alignment should be.
// However, there *is* an aligned func defined above.
// Maybe 1 is fine?
void *ptr = pk_new_bkt(size, 1, MemBkt_Bullet);
pk_arr_append_t(&bulletAllocs, {ptr, size});
return ptr;
}
void pke_btFreeFunc(void *memBlock) {
int64_t index = -1;
uint32_t i, count;
count = bulletAllocs.next;
for (i = 0; i < count; ++i) {
if (bulletAllocs[i].data == memBlock) {
index = i;
break;
}
}
assert(index != -1);
pk_delete_bkt(memBlock, bulletAllocs[index].size, MemBkt_Bullet);
pk_arr_remove_at(&bulletAllocs, index);
}
struct CollisionHandlerStruct : public btOverlapFilterCallback {
~CollisionHandlerStruct() override {}
bool needBroadphaseCollision(btBroadphaseProxy* proxy0, btBroadphaseProxy* proxy1) const override {
EntityCollision col;
auto collided = (proxy0->m_collisionFilterGroup & proxy1->m_collisionFilterMask) |
(proxy1->m_collisionFilterGroup & proxy0->m_collisionFilterMask);
if (collided) {
const auto *col0 = static_cast<btCollisionObject *>(proxy0->m_clientObject);
const auto *col1 = static_cast<btCollisionObject *>(proxy1->m_clientObject);
if (col0 && col1) {
CompInstance *ent0 = reinterpret_cast<CompInstance *>(col0->getUserPointer());
CompInstance *ent1 = reinterpret_cast<CompInstance *>(col1->getUserPointer());
if (ent0 != nullptr && ent1 != nullptr) {
col.a = ent0;
col.b = ent1;
pk_arr_append(&collisionsThisTick, &col);
}
}
}
return collided;
}
} collisionHandlerStruct;
void Physics_Init() {
MemBkt_Bullet = pk_mem_bucket_create("physics", PK_MEM_DEFAULT_BUCKET_SIZE, PK_MEMBUCKET_FLAG_NONE);
bulletAllocs.bkt = MemBkt_Bullet;
pk_arr_reserve(&bulletAllocs, 1024);
btAlignedAllocSetCustom(pke_btAllocFunc, pke_btFreeFunc);
btAlignedAllocSetCustomAligned(pke_btAlignedAllocFunc, pke_btAlignedFreeFunc);
btConfiguration = pk_new<btDefaultCollisionConfiguration>(MemBkt_Bullet);
btDispatcher = pk_new<btCollisionDispatcher>(MemBkt_Bullet);
new (btDispatcher) btCollisionDispatcher(btConfiguration);
btBroadphase = pk_new<btDbvtBroadphase>(MemBkt_Bullet);
#if 1
overlappingPairCache = pk_new<btHashedOverlappingPairCache>(MemBkt_Bullet);
overlappingPairCache->setOverlapFilterCallback(&collisionHandlerStruct);
new (btBroadphase) btDbvtBroadphase(overlappingPairCache);
#else
new (btBroadphase) btDbvtBroadphase();
#endif
btSolver = pk_new<btSequentialImpulseConstraintSolver>(MemBkt_Bullet);
BtDynamicsWorld = pk_new<btDiscreteDynamicsWorld>(MemBkt_Bullet);
new (BtDynamicsWorld) btDiscreteDynamicsWorld(btDispatcher, btBroadphase, btSolver, btConfiguration);
}
int32_t Physics_Tick(double delta) {
if (pkeSettings.isSimulationPaused == true)
return 0;
pk_arr_clear(&collisionsThisTick);
auto tickCount = BtDynamicsWorld->stepSimulation(delta, 1);
for (long i = 0; i < collisionsThisTick.next; ++i) {
ECS_HandleCollision(collisionsThisTick[i].a, collisionsThisTick[i].b);
}
return tickCount;
}
void Physics_Teardown() {
pk_arr_reset(&collisionsThisTick);
if (BtDynamicsWorld != nullptr)
pk_delete<btDiscreteDynamicsWorld>(BtDynamicsWorld, MemBkt_Bullet);
if (overlappingPairCache != nullptr)
pk_delete<btHashedOverlappingPairCache>(overlappingPairCache, MemBkt_Bullet);
if (btConfiguration != nullptr)
pk_delete<btDefaultCollisionConfiguration>(btConfiguration, MemBkt_Bullet);
if (btSolver != nullptr)
pk_delete<btSequentialImpulseConstraintSolver>(btSolver, MemBkt_Bullet);
if (btDispatcher != nullptr)
pk_delete<btCollisionDispatcher>(btDispatcher, MemBkt_Bullet);
if (btBroadphase != nullptr)
pk_delete<btDbvtBroadphase>(btBroadphase, MemBkt_Bullet);
btConfiguration = nullptr;
btSolver = nullptr;
btBroadphase = nullptr;
btDispatcher = nullptr;
BtDynamicsWorld = nullptr;
// TODO should we manually delete each bullet alloc?
// or just drop?
pk_arr_reset(&bulletAllocs);
pk_mem_bucket_destroy(MemBkt_Bullet);
}
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