If you have entities that will be rotating, you can either modify the dimensions of the bounding box so it still wraps the object, or opt to use another bounding geometry type, such as spheres which are invariant to rotation. The box constantly changes dimensions to snugly fit the entity contained inside. Note: Check out the Bounding Volumes with Three.
Checking if a point is inside an AABB is pretty simple — we just need to check whether the point's coordinates fall inside the AABB; considering each axis separately. We just need to do one test per axis, using the boxes' boundaries.
Using bounding spheres to detect collisions is a bit more complex than AABB, but still fairly quick to test. The main advantage of spheres is that they are invariant to rotation, so if the wrapped entity rotates, the bounding sphere would still be the same. Their main disadvantage is that unless the entity they are wrapping is actually spherical, the wrapping is usually not a good fit i. To check whether a sphere contains a point we need to calculate the distance between the point and the sphere's center.
So we check if the horizontal edges overlap, and if the vertical edges overlap of both objects. If both the horizontal and vertical edges overlap we have a collision. Translating this concept to code is relatively straightforward. We check for overlap on both axes and if so, return a collision:. We check if the right side of the first object is greater than the left side of the second object and if the second object's right side is greater than the first object's left side; similarly for the vertical axis.
To keep the collision code a bit more organized we add an extra function to the Game class:. Within DoCollisions , we check for collisions between the ball object and each brick of the level. If we detect a collision, we set the brick's Destroyed property to true , which instantly stops the level from rendering this brick:. If we run the code now, the ball should detect collisions with each of the bricks and if the brick is not solid, the brick is destroyed.
If you run the game now it'll look something like this:. While the collision detection does work, it's not very precise since the ball's rectangular collision shape collides with most of the bricks without the ball directly touching them. Let's see if we can figure out a more precise collision detection technique.
Because the ball is a circle-like object, an AABB is probably not the best choice for the ball's collision shape. The collision code thinks the ball is a rectangular box, so the ball often collides with a brick even though the ball sprite itself isn't yet touching the brick. It makes much more sense to represent the ball with a circle collision shape instead of an AABB. For this reason we included a Radius variable within the ball object.
These systems will override the driver, changing the throttle of the vehicle or applying the brakes. The tools to inform these systems are similar to alerts, including radar, lasers, and cameras, however the response of the vehicle is more proactive.
Collision avoidance features that actively assist drivers include:. Adaptive Cruise Control: More preventative than reactive, these systems use radar or lasers to adjust your cruise control speed via throttle to maintain an appropriate distance from the vehicle in front of you. Automatic Emergency Braking AEB : Brakes are automatically applied based on feedback from sensors in order to prevent a collision or minimize collision speed. Rear Automatic Emergency Braking: Brakes are automatically applied to prevent the vehicle from backing into an object using a cross-traffic monitoring system or sensors like radar or lasers.
Electronic Stability Control ESC : An extension of antilock brake technology, ESC automatically applies your brakes to help steer the car appropriately during a loss of traction. An onboard computer monitors various sensors to determine which wheels to brake and which to accelerate.
Parking Assist: Feedback from cameras and sensors combine to allow vehicles to steer themselves into a parking space while the driver controlling the speed.
The most sophisticated developments in collision avoidance are being achieved by combining information from multiple sensors and systems. As these systems become more advanced and synergized, we will begin to realize the lofty goals set by automakers for increased safety and, eventually, self-driving vehicles.
At least for a few more years.
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