.gitignore

@@ -1,3 +1,6 @@
+# ide files
+.nvimrc
+
 # build dirs
 bin/
 release/
@@ -8,3 +11,4 @@ compile_commands.json
 
 # clangd cache
 .cache/
+.helix

src/corelib/render.c

@@ -80,10 +80,10 @@ static
 void _exec_sprite_cmd(const drawcmd_t* cmd) {
 	const sprite_t* sprite = &cmd->sprite;
 	SDL_FRect untransformed = {sprite->x, sprite->y, sprite->sx, sprite->sy};
+	untransformed.x -= sprite->origin.x;
+	untransformed.y -= sprite->origin.y;
 	SDL_FRect destrect = get_dest_with_size(untransformed, cmd->ui);
 	SDL_FPoint origin = {destrect.w * sprite->origin.x, destrect.h * sprite->origin.y};
-	destrect.x -= origin.x;
-	destrect.y -= origin.y;
 	SDL_RenderCopyExF(g_context.renderer, sprite->texture,
 					  &sprite->uv, &destrect, sprite->rot,
 					  &origin, sprite->flip);
@@ -443,7 +443,7 @@ sprite_t make_sprite(const char* file, float x, float y) {
 	sprite_t sprite=(sprite_t){
 		.texture=get_texture(file),
 		.x=x,.y=y,
-		.origin=(SDL_FPoint){.x=0,.y=0},
+		.origin=(SDL_FPoint){.x=0.0,.y=0.0},
 		.sx=1.0,.sy=1.0,
 		.rot=0,
 		.depth=RLAYER_SPRITES,
@@ -451,7 +451,6 @@ sprite_t make_sprite(const char* file, float x, float y) {
 		.flip=SDL_FLIP_NONE,
 	};
 	SDL_QueryTexture(sprite.texture, NULL, NULL, &sprite.uv.w, &sprite.uv.h);
-	sprite.origin.x = -(float)sprite.uv.h/2.f; sprite.origin.y = -(float)sprite.uv.h/2.f;
 	return sprite;
 }
 

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 +65,142 @@ void draw_objects() {
 		}
 	}
 }
+
+static inline
+int _rect_overlap(float aminx, float aminy, float amaxx, float amaxy, float bminx, float bminy, float bmaxx, float bmaxy) {
+	return
+	(
+		(aminx < bmaxx && aminx > bmaxx) 
+		||
+		(amaxx > bminx && amaxx < bmaxx)
+	) && (
+		(aminy < bmaxy && aminy > bmaxy)
+		||
+		(amaxy > bminy && amaxy < bmaxy)
+	);
+}
+
+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 _rect_overlap(aminx, aminy, amaxx, amaxy, bminx, bminy, bmaxx, 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; ++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);
+			}
+		}
+	}
+}
+
+object_t* interpolate_move(object_t* object, float target_x, float target_y, float max_step_size) {
+	// calculate step delta
+	float dx = target_x - object->sprite.x, dy = target_y - object->sprite.y;
+	// calculate direction x,y
+	float m = sqrtf(dx*dx + dy*dy);
+	dx /= m; dy /= m;
+	dx *= max_step_size; dy *= max_step_size;
+
+	// ensure this object would ever collide
+	// if it wouldn't collide anyway, just set position
+	if(_can_collide(object)) {
+		object->sprite.x = target_x;
+		object->sprite.y = target_y;
+		return NULL;
+	}
+
+	/*
+	 * 1. check collision with every other object
+	 * 2. move towards target
+	 */
+	while(object->sprite.x != target_x || object->sprite.y != target_y) {
+		for(int i = 0; i < WORLD_NUM_OBJECTS; ++i) {
+			object_t* other = g_objects + i;
+			if(!_can_collide(other)) continue;
+			if(object != other && _collision_check(other, object)) {
+				other->collider.evt_collision(other, object);
+				object->collider.evt_collision(object, other);
+				return other;
+			}
+		}
+
+		// move towards target, snap to target if distance is too low
+		float distx = fabsf(object->sprite.x - target_x), disty = fabsf(object->sprite.y - target_y);
+		if(distx < fabsf(dx) && disty < fabsf(dy)) {
+			object->sprite.x += dx; object->sprite.y += dy;
+		} else {
+			object->sprite.x = target_x;
+			object->sprite.y = target_y;
+		}
+	}
+
+	// no collision, return nothing
+	return NULL;
+}

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 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 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 +48,19 @@ 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();
+
+object_t* interpolate_move(object_t* object, float target_x, float target_y, float max_step_size);
+
 #endif /* _world_h */