Fix interval overlap case for collision detection

If one interval were completely contained within another then the logic would
not correctly identify the overlap. Instead check the length of the intervals
and ensure the smaller interval of the two is compared against the larger one.

src/Asteroid.c

@@ -389,6 +389,34 @@ b32 moveEntity(GameState *state, Entity *entity, i32 entityIndex, v2 ddP,
 	return willCollide;
 }
 
+INTERNAL void addAsteroid(GameState *state, v2 windowSize)
+{
+	Entity *asteroid = &state->entityList[state->entityIndex];
+	asteroid->id     = state->entityIndex++;
+
+	i32 randValue = rand();
+	i32 randX     = (randValue % (i32)windowSize.w);
+	i32 randY     = (randValue % (i32)windowSize.h);
+	asteroid->pos = V2i(randX, randY);
+
+	asteroid->size       = V2(75.0f, 75.0f);
+	asteroid->hitbox     = asteroid->size;
+	asteroid->offset     = V2(asteroid->size.w * -0.5f, 0);
+	asteroid->scale      = 1;
+	asteroid->rotation   = 45;
+	asteroid->type       = entitytype_asteroid;
+	asteroid->direction  = direction_null;
+	asteroid->renderMode = rendermode_polygon;
+
+	asteroid->numVertexPoints = 10;
+	asteroid->vertexPoints    = createAsteroidVertexList(
+	    &state->persistentArena, asteroid->numVertexPoints,
+	    (i32)(asteroid->size.x * 0.5f));
+
+	asteroid->tex      = NULL;
+	asteroid->collides = TRUE;
+}
+
 void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
                                   v2 windowSize, f32 dt)
 {
@@ -406,34 +434,9 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
 		state->pixelsPerMeter = 70.0f;
 
 		{ // Init asteroid entities
-			i32 numAsteroids = 1;
+			i32 numAsteroids = 15;
 			for (i32 i = 0; i < numAsteroids; i++)
-			{
+				addAsteroid(state, windowSize);
-				Entity *asteroid = &state->entityList[state->entityIndex];
-				asteroid->id     = state->entityIndex++;
-
-				i32 randValue = rand();
-				i32 randX     = (randValue % (i32)windowSize.w);
-				i32 randY     = (randValue % (i32)windowSize.h);
-				asteroid->pos = V2i(100 + (i * 100), 500);
-
-				asteroid->size       = V2(100.0f, 100.0f);
-				asteroid->hitbox     = asteroid->size;
-				asteroid->offset     = V2(asteroid->size.w * -0.5f, 0);
-				asteroid->scale      = 1;
-				asteroid->rotation   = 45;
-				asteroid->type       = entitytype_asteroid;
-				asteroid->direction  = direction_null;
-				asteroid->renderMode = rendermode_polygon;
-
-				asteroid->numVertexPoints = i + 10;
-				asteroid->vertexPoints    = createAsteroidVertexList(
-						&state->persistentArena, asteroid->numVertexPoints,
-						(i32)(asteroid->size.x * 0.5f));
-
-				asteroid->tex      = NULL;
-				asteroid->collides = TRUE;
-			}
 		}
 
 #if 1
@@ -503,6 +506,12 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
 		}
 	}
 
+	if (getKeyStatus(&state->input.keys[keycode_left_square_bracket],
+	                 readkeytype_repeat, 0.2f, dt))
+	{
+		addAsteroid(state, windowSize);
+	}
+
 	for (i32 i = 0; i < state->entityIndex; i++)
 	{
 		Entity *entity = &state->entityList[i];
@@ -574,7 +583,7 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
 			}
 
 			v2 ddP = {0};
-#if 0
+#if 1
 			switch (entity->direction)
 			{
 			case direction_north:
@@ -642,8 +651,8 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
 			// NOTE(doyle): Make asteroids start and move at constant speed
 			ddPSpeedInMs = 1;
 			entity->dP   = v2_scale(ddP, state->pixelsPerMeter * ddPSpeedInMs);
-#endif
 			entity->rotation += (60 * dt);
+#endif
 		}
 
 		b32 willCollide = moveEntity(state, entity, i, ddP, dt, ddPSpeedInMs);
@@ -661,7 +670,7 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
 		                entityColor, flags);
 	}
 
-#if 0
+#if 1
 	debug_drawUi(state, dt);
 	debug_clearCounter();
 #endif

src/include/Dengine/Math.h

@@ -191,9 +191,20 @@ INTERNAL inline v2 v2_normalise(const v2 a)
 	return result;
 }
 
-INTERNAL inline b32 v2_intervalsOverlap(const v2 a, const v2 b) 
+INTERNAL inline b32 v2_intervalsOverlap(v2 a, v2 b)
 {
 	b32 result = FALSE;
+	
+	f32 lenOfA = a.max - a.min;
+	f32 lenOfB = b.max - b.min;
+
+	if (lenOfA > lenOfB)
+	{
+		v2 tmp = a;
+		a      = b;
+		b      = tmp;
+	}
+
 	if ((a.min >= b.min && a.min <= b.max) ||
 	    (a.max >= b.min && a.max <= b.max))
 	{