Class PhysicsIntegration

Namespace

Thunder.UnitsNET.Vectors.Geometry

Assembly

Thunder.UnitsNET.Vectors.Geometry.dll

Pure utility methods for updating entity state each game tick. Codifies correct unit algebra for Euler/Verlet integration, drag, friction, and collision push-out.

public static class PhysicsIntegration

Inheritance

object

PhysicsIntegration

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Examples

// Typical game loop:
var position = LengthPoint2.FromMeters(0, 0);
var velocity = SpeedVector2.FromMetersPerSecond(1, 0);
var dt = Duration.FromSeconds(0.016);
position = PhysicsIntegration.Euler(position, velocity, dt);
velocity = PhysicsIntegration.Euler(velocity, AccelerationVector2.FromMetersPerSecondSquared(0, -9.8), dt);

Methods

ApplyDrag(SpeedVector2, double, Duration)

Applies exponential drag to a velocity: velocity × exp(−dragCoefficient × dt).

public static SpeedVector2 ApplyDrag(SpeedVector2 velocity, double dragCoefficient, Duration dt)

Parameters

velocity SpeedVector2

Current velocity vector.

dragCoefficient double

Drag coefficient (s⁻¹). Higher values decay velocity faster. A coefficient of 0 returns the velocity unchanged.

dt Duration

Time step duration.

Returns

SpeedVector2

Velocity after applying drag.

Remarks

Models linear drag (air resistance proportional to velocity). The exponential decay maintains direction and smoothly decays magnitude toward zero without overshooting.

ApplyFriction(SpeedVector2, AccelerationVector2, double, Duration)

Applies Coulomb (sliding) friction to a velocity, decelerating it toward zero.

public static SpeedVector2 ApplyFriction(SpeedVector2 velocity, AccelerationVector2 gravity, double mu, Duration dt)

Parameters

velocity SpeedVector2

Current velocity vector.

gravity AccelerationVector2

Gravity vector (used for its magnitude; direction is ignored).

mu double

Friction coefficient (dimensionless). 0 = frictionless; typical: 0.3–0.8.

dt Duration

Time step duration.

Returns

SpeedVector2

Velocity after applying friction.

Remarks

Friction deceleration magnitude is mu × |gravity|. Applied as an impulse over dt. If the friction impulse would exceed the current speed, the velocity is clamped to zero (no reversal).

Euler(LengthPoint2, SpeedVector2, Duration)

Advances a position by one Euler step: position + velocity × dt.

public static LengthPoint2 Euler(LengthPoint2 position, SpeedVector2 velocity, Duration dt)

Parameters

position LengthPoint2

Current world-space position.

velocity SpeedVector2

Current velocity vector.

dt Duration

Time step duration.

Returns

LengthPoint2

New position after the step.

Euler(SpeedVector2, AccelerationVector2, Duration)

Advances a velocity by one Euler step: velocity + acceleration × dt.

public static SpeedVector2 Euler(SpeedVector2 velocity, AccelerationVector2 acceleration, Duration dt)

Parameters

velocity SpeedVector2

Current velocity vector.

acceleration AccelerationVector2

Current acceleration vector (e.g., gravity).

dt Duration

Time step duration.

Returns

SpeedVector2

New velocity after the step.

Resolve(LengthPoint2, CollisionManifold)

Resolves a collision by applying the manifold push-out to a position: position + manifold.PushOut.

public static LengthPoint2 Resolve(LengthPoint2 position, CollisionManifold manifold)

Parameters

position LengthPoint2

Current world-space position of body A.

manifold CollisionManifold

Collision manifold produced by a shape overlap test.

Returns

LengthPoint2

New position with the overlap resolved.

Remarks

The push-out is ContactNormal × PenetrationDepth, pointing from the other body toward this one. Apply this to body A's position to fully separate A from B.

Verlet(LengthPoint2, SpeedVector2, AccelerationVector2, Duration)

Advances position and velocity by one Velocity Verlet step. Position uses a second-order correction: position + velocity × dt + ½ × acceleration × dt². Velocity uses the first-order update: velocity + acceleration × dt.

public static (LengthPoint2 position, SpeedVector2 velocity) Verlet(LengthPoint2 position, SpeedVector2 velocity, AccelerationVector2 acceleration, Duration dt)

Parameters

position LengthPoint2

Current world-space position.

velocity SpeedVector2

Current velocity vector.

acceleration AccelerationVector2

Current acceleration vector.

dt Duration

Time step duration.

Returns

(LengthPoint2 position, SpeedVector2 velocity)

Tuple of (new position, new velocity) after the step.

Remarks

The second-order position update makes Verlet more accurate than Euler for constant-acceleration problems (e.g., projectile motion under gravity). Full Velocity Verlet requires re-evaluating forces after the position update; for the simplified single-acceleration form used here, the velocity result is equivalent to Euler.