From 6c16e8cdbd2bc6fa68647b852bf514f5599f0f6f Mon Sep 17 00:00:00 2001 From: Sara Date: Wed, 24 May 2023 21:31:50 +0200 Subject: [PATCH] implemented simple aabb and circle collision --- src/corelib/world.c | 96 +++++++++++++++++++++++++++++++++++++++++++++ src/corelib/world.h | 31 ++++++++++++++- 2 files changed, 125 insertions(+), 2 deletions(-) diff --git a/src/corelib/world.c b/src/corelib/world.c index 6f62c91..11a26f6 100644 --- a/src/corelib/world.c +++ b/src/corelib/world.c @@ -26,6 +26,7 @@ object_t* make_object() { object_t* o = _find_free_object(); o->active = 1; o->enabled = 1; + o->collider = collider_default(); o->evt_draw = &object_draw_sprite; o->evt_update = NULL; memset(&o->sprite, 0, sizeof(sprite_t)); @@ -39,6 +40,12 @@ object_t* instantiate_object(const object_t *original) { return obj; } +collider_t collider_default() { + return (collider_t) { + .type=COLLIDERTYPE_NONE + }; +} + void update_objects() { for(int i = 0; i < WORLD_NUM_OBJECTS; ++i) { if(g_objects[i].active == 1 @@ -58,3 +65,92 @@ void draw_objects() { } } } + +static inline +short _collision_aabb_aabb(const object_t* a, const object_t* b) { + const float aminx = a->collider.aabb.x + a->sprite.x, aminy = a->collider.aabb.y + a->sprite.x; + const float amaxx = aminx + a->collider.aabb.w, amaxy = aminy + a->collider.aabb.h; + const float bminx = b->collider.aabb.x, bminy = b->collider.aabb.y; + const float bmaxx = b->collider.aabb.x + b->collider.aabb.w, bmaxy = b->collider.aabb.y + b->collider.aabb.h; + + return + ( + (aminx < bmaxx && aminx > bmaxx) + || + (amaxx > bminx && amaxx < bmaxx) + ) && ( + (aminy < bmaxy && aminy > bmaxy) + || + (amaxy > bminy && amaxy < bmaxy) + ); +} + +static inline +short _collision_circle_circle(const object_t* a, const object_t* b) { + const float ax = a->sprite.x + a->collider.circle.x, ay = a->sprite.y + a->collider.circle.y, + bx = b->sprite.x + b->collider.circle.x, by = b->sprite.y + b->collider.circle.y; + const float dx = fabsf(ax-bx), dy = fabsf(ay-by); + const float sqrdist = dx*dx+dy*dy; + const float mindist = a->collider.circle.radius + b->collider.circle.radius; + const float mindistsqr = mindist*mindist; + return sqrdist < mindistsqr; +} + +static inline +float fclampf(float x, float min_, float max_) { + return fminf(max_, fmaxf(min_, x)); +} + +static inline +short _collision_circle_aabb(const object_t* circle, const object_t* aabb) { + // generate a point on the edge of the rectangle that is closest to the circle + const float bbminx = aabb->collider.aabb.x + aabb->sprite.x, bbmaxx = bbminx + aabb->collider.aabb.w, + bbminy = aabb->collider.aabb.y + aabb->sprite.x, bbmaxy = bbminy + aabb->collider.aabb.h; + const float cx = circle->sprite.x + circle->collider.circle.x, + cy = circle->sprite.y + circle->collider.circle.y; + const float x = fclampf(cx, bbminx, bbmaxx), + y = fclampf(cy, bbminy, bbmaxy); + const float dx = fabsf(cx - x), dy = fabsf(cy - y); + + // calculate the square distance from the centre of the circle to the edge of the aabb + const float distsqr = dx*dx+dy*dy; + const float rsqr = circle->collider.circle.radius*circle->collider.circle.radius; + + // return if the square distance is larger than the square of the radius + return distsqr < rsqr; +} + +static inline +short _collision_check(const object_t* a, const object_t* b) { + if(a->collider.type == COLLIDERTYPE_AABB && b->collider.type == COLLIDERTYPE_AABB) { + return _collision_aabb_aabb(a, b); + } else if(a->collider.type == COLLIDERTYPE_CIRCLE && b->collider.type == COLLIDERTYPE_CIRCLE) { + return _collision_circle_circle(a, b); + } else if(a->collider.type == COLLIDERTYPE_CIRCLE && b->collider.type == COLLIDERTYPE_AABB) { + return _collision_circle_aabb(a, b); + } else if(a->collider.type == COLLIDERTYPE_AABB && b->collider.type == COLLIDERTYPE_CIRCLE) { + return _collision_circle_aabb(b, a); + } + return 0; +} + +static inline +short _can_collide(const object_t* object) { + return object->active && object->enabled && object->collider.evt_collision != NULL; +} + +void update_collision() { + for(int outer = 0; outer < WORLD_NUM_OBJECTS; ++outer) { + object_t* oobject = g_objects + outer; + if(!_can_collide(oobject)) continue; + for(int inner = 0; inner < WORLD_NUM_OBJECTS/2; ++inner) { + object_t* iobject = g_objects + inner; + if(!_can_collide(oobject)) continue; + + if(outer != inner && _collision_check(iobject, oobject)) { + oobject->collider.evt_collision(oobject, iobject); + iobject->collider.evt_collision(iobject, oobject); + } + } + } +} diff --git a/src/corelib/world.h b/src/corelib/world.h index 2fd381d..884b23f 100644 --- a/src/corelib/world.h +++ b/src/corelib/world.h @@ -10,11 +10,33 @@ typedef struct object_t object_t; typedef void(*tick_fn)(struct object_t*); typedef void(*draw_fn)(struct object_t*); +typedef void(*collided_fn)(struct object_t*, struct object_t*); + +typedef enum collider_type_t { + COLLIDERTYPE_MIN, + COLLIDERTYPE_NONE, + COLLIDERTYPE_CIRCLE, + COLLIDERTYPE_AABB, + COLLIDERTYPE_MAX, +} collider_type_t; + +typedef struct collider_t { + collider_type_t type; + collided_fn evt_collision; + union { + struct { + float x, y; + float radius; + } circle; + SDL_FRect aabb; + }; +} collider_t; struct object_t { sprite_t sprite; - int active; // 1 if this object is in use and should not be overriden - int enabled; // 1 if this object's events should be triggered + int active; // 1 if this object is in use and should not be overriden. + int enabled; // 1 if this object's events should be triggered. + collider_t collider; // the collider to use for this object's physics interaction. uintptr_t timer; // free to use for whatever @@ -26,12 +48,17 @@ extern object_t g_objects[WORLD_NUM_OBJECTS]; void world_clear(); + object_t* make_object(); object_t* instantiate_object(const object_t* original); +collider_t collider_default(); + void object_draw_sprite(object_t* object); void update_objects(); void draw_objects(); +void update_collision(); + #endif /* _world_h */