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[kabbotta]

I have very simple collision requirements. I need circles to collide with circles and circles to collide with 1x1 tiles. I have written up a method to try and handle the circle-tile collisions and it isn't quite working. Any help would be appreciated.

First, I scan for collisions depending on which way the entity is moving.

Code:

void PhysicsSystem::scan_collisions(DynamicEntity& entity)
{
  int px, py;

  px = (int)std::floor(entity.pos.x());
  py = (int)std::floor(entity.pos.y());

  if (entity.vel.x() > 0)
  {
    for (auto y = py - 1; y <= py + 1; ++y)
    {
      if ((px + 1) < 0 || (px + 1) >= MAP_SIZE_X || y < 0 || y >= MAP_SIZE_Y)
	continue;

      if (map_system.get_tile((px + 1), y, entity.floor).solid)
	resolve_collision(entity, (px + 1), y);
    }
  }
  else if (entity.vel.x() < 0)
  {
    for (auto y = py - 1; y <= py + 1; ++y)
    {
      if ((px - 1) < 0 || (px - 1) >= MAP_SIZE_X || y < 0 || y >= MAP_SIZE_Y)
	continue;

      if (map_system.get_tile((px - 1), y, entity.floor).solid)
	resolve_collision(entity, (px - 1), y);
    }
  }

  ... [same for y-direction]
}

And here is the resolution method:

Code:

void PhysicsSystem::resolve_collision(DynamicEntity& entity, int x, int y)
{
  Vector2f tile_pos(x, y);
  Vector2f nearest(entity.pos);
  Vector2f min(x, y), max(x + 1, y + 1);

  if (nearest.x() < min.x()) nearest.x() = min.x();
  else if (nearest.x() > max.x()) nearest.x() = max.x();

  if (nearest.y() < min.y()) nearest.y() = min.y();
  else if (nearest.y() > max.y()) nearest.y() = max.y();

  Vector2f ray(entity.pos - nearest);
  auto length = ray.norm();
  auto depth = entity.size - length;

  if (length != 0 && depth > 0)
  {
    ray.normalize();
    entity.pos += depth * ray;
  }
}

But this collides too soon when the player is walking to the left or walking up and hits a tile.