Body
Setting body physics
Mass
The weight of the vehicle in kilograms.
Continuous collision detection (CCD)
When simulating physics in a game or animation, a fast-moving object can sometimes pass through thin obstacles without any collision being detected. This happens because the object moves so quickly that it skips over the obstacle in a single simulation step.
While you could reduce the time step to catch these collisions, this makes the simulation much slower and less efficient.
A better solution is to use Continuous Collision Detection (CCD). CCD checks for collisions between steps by treating the moving object as a sphere that sweeps along its path, detecting any obstacles it might hit.
CCD is turned off by default because it uses more computing power. You should enable it only for fast-moving objects.
For best results, adjust both the motion threshold and the size of the swept sphere. Here's a simple rule of thumb: make sure the threshold and sphere size are balanced based on how fast your object moves.
CCD_Swept_Radius_Sphere - Sphere radius
CCD_Motion_Threshold - Distance per time step
Restution
When responsive rigid bodies collide, contact forces come into play, altering their velocities. These forces are split into 2 components: restitution and friction. Restitution is a force parallel to the contact normal. Its strength hints at what the bodies might be made out of.
If both bodies were made of hard, springy steel, they might separate without loss of kinetic energy, after undergoing what’s called a perfectly elastic collision. If, on the other hand, both bodies were made of soft, sticky clay, they might cling together, dissipating kinetic energy and undergoing what’s called a perfectly inelastic collision.
In reality, no collision is perfectly elastic. Elasticity is quantified by a coefficient of restitution, which ranges from zero (perfectly inelastic) to one (perfectly elastic).
In simulation, collisions are inelastic by default. Each rigid body has a restitution parameter, which defaults to zero. For each collision, the coefficient of restitution is calculated by multiplying the parameters of the colliding bodies.
To simulate a perfectly elastic collision, set the restitution parameters of both bodies to 1.
Friction
While restitution models contact forces parallel to the contact normal, friction models contact forces orthogonal to the contact normal.
Each rigid body has a friction parameter (which defaults to 0.5). This parameter hints at the body’s surface characteristics. Reducing a body’s friction parameter makes it more slippery (think wet ice). Increasing it yields better traction (think sandpaper or dry rubber).
For each collision, a coefficient of friction is calculated by multiplying the parameters of the colliding bodies.
Factor
All forces, torques, and impulses acting on dynamic rigid bodies are multiplied by factors that can be configured for each body.
Damping
In the absence of external forces, inertia would keep the velocities of a dynamic body constant. In the real world, however, we’re accustomed to seeing unpowered moving objects eventually come to rest. This behavior is often caused by drag forces (such as air resistance) that increase with speed.
To simulate drag forces, each rigid body has damping, which quantifies how quickly its motion decays to zero, assuming the body is dynamic.
More precisely, each body has 2 damping parameters: linear damping and angular damping, each of which ranges from zero (no drag) to one (motion ceases immediately). Linear damping damps the linear velocity, and angular damping damps the angular velocity.
Bounding Boxes
Is a virtual boxes that is used to represent the boundaries of an object's physical body in three-dimensional space. It defines the space occupied by the object and is used for various calculations such as collisions, intersection detection.
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