public static bool SpherePlaneCollisionOccured(PSI_Collider_Sphere sphereCol, PSI_Collider_Plane planeCol, out Vector3 point)
{
// Determine the signed distance to from the sphere to its projected point on the plane.
float distToProjectedPoint = Vector3.Dot(planeCol.pNormal, (sphereCol.pPosition - planeCol.pPosition));
// Determine the spheres projected point on the plane.
point = sphereCol.pPosition - distToProjectedPoint * planeCol.pNormal;
// Generate 4 triangles between the corners of the plane and the projected point.
var planeVerts = planeCol.GetVertices();
var triangles = new Vector3[4, 3];
for (int i = 0; i < 4; i++)
{
triangles[i, 0] = point;
triangles[i, 1] = planeVerts[i];
triangles[i, 2] = planeVerts[(i == 3) ? 0 : i + 1];
}
// Sum the area of the traingles.
float totalTriArea = 0.0f;
for (int i = 0; i < 4; i++)
{
float a = Vector3.Distance(triangles[i, 0], triangles[i, 1]);
float b = Vector3.Distance(triangles[i, 1], triangles[i, 2]);
float c = Vector3.Distance(triangles[i, 2], triangles[i, 0]);
float s = (a + b + c) / 2;
totalTriArea += Mathf.Sqrt(s * (s - a) * (s - b) * (s - c));
}
// Determine if a collision occured by checking if the sphere is overlapping with the plane and the projected point
// is within the extents of the plane by checking the sum area of the triangles is equal to the size of the plane.
bool isColliding = Mathf.Abs(totalTriArea - planeCol.pArea) < 0.01f && Mathf.Abs(distToProjectedPoint) <= sphereCol.pRadius;
if (isColliding)
{
// Resolve any overlap between the sphere and the plane.
var collisionAxis = CorrectCollisionAxisDirection(planeCol.pPosition, sphereCol.pPosition, point - sphereCol.pPosition);
var overlap = collisionAxis.magnitude - sphereCol.pRadius;
ResolveCollisionOverlaps(sphereCol, planeCol, collisionAxis, overlap);
// Calculate and apply the collision impulse to the sphere.
ApplyImpulses(sphereCol, planeCol, collisionAxis, point);
// Apply friction to the sphere.
ApplyFriction(sphereCol, planeCol, point);
return(true);
}
return(false);
}
private static void ApplyFriction(PSI_Collider col, PSI_Collider_Plane planeCol, Vector3 collisionPoint)
{
// Calculating and applying friction to a body moving along a plane.
if (!col.pRigidbody)
{
return;
}
var incline = Vector3.Angle(Vector3.up, planeCol.pNormal);
var normalForce = col.pRigidbody.Mass * 9.81f * Mathf.Cos(incline);
var coeffFriction = col.pRigidbody.CoeffOfFrict;
var friction = coeffFriction * normalForce;
col.pRigidbody.AddFrictionAtPoint(friction * -col.pRigidbody.Velocity.normalized, collisionPoint);
}
//------------------------------------Private Functions-------------------------------------
private void CheckForCollision(PSI_Collider col1, PSI_Collider col2)
{
bool collisionOccurred = false;
PSI_Collision collision = new PSI_Collision();
collision.col1 = col1;
collision.col2 = col2;
// Sphere on sphere.
if (col1.pType == ColliderType.Sphere && col2.pType == ColliderType.Sphere)
{
collisionOccurred = PSI_PhysicsUtils.SphereSphereCollisionCheck((PSI_Collider_Sphere)col1, (PSI_Collider_Sphere)col2, out collision.point);
}
// Sphere on plane.
if ((col1.pType == ColliderType.Sphere && col2.pType == ColliderType.Plane) ||
(col1.pType == ColliderType.Plane && col2.pType == ColliderType.Sphere))
{
PSI_Collider_Sphere sphere = (PSI_Collider_Sphere)((col1.pType == ColliderType.Sphere) ? col1 : col2);
PSI_Collider_Plane plane = (PSI_Collider_Plane)((col1.pType == ColliderType.Sphere) ? col2 : col1);
if (PSI_PhysicsUtils.SpherePlaneCollisionOccured(sphere, plane, out collision.point))
{
collisionOccurred = true;
}
}
// Sphere on box.
if ((col1.pType == ColliderType.Sphere && col2.pType == ColliderType.Box) ||
(col1.pType == ColliderType.Box && col2.pType == ColliderType.Sphere))
{
PSI_Collider_Sphere sphere = (PSI_Collider_Sphere)((col1.pType == ColliderType.Sphere) ? col1 : col2);
PSI_Collider_Box box = (PSI_Collider_Box)((col1.pType == ColliderType.Sphere) ? col2 : col1);
if (PSI_PhysicsUtils.SphereBoxCollisionOccured(sphere, box, out collision.point))
{
collisionOccurred = true;
}
}
// Box on box.
if ((col1.pType == ColliderType.Box && col2.pType == ColliderType.Box))
{
if (PSI_PhysicsUtils.BoxBoxCollisionOccured((PSI_Collider_Box)col1, (PSI_Collider_Box)col2, out collision.point))
{
collisionOccurred = true;
}
}
// Box on plane.
if ((col1.pType == ColliderType.Box && col2.pType == ColliderType.Plane) ||
(col1.pType == ColliderType.Plane && col2.pType == ColliderType.Box))
{
PSI_Collider_Box box = (PSI_Collider_Box)((col1.pType == ColliderType.Box) ? col1 : col2);
PSI_Collider_Plane plane = (PSI_Collider_Plane)((col1.pType == ColliderType.Box) ? col2 : col1);
if (PSI_PhysicsUtils.BoxPlaneCollisionOccured(box, plane, out collision.point))
{
collisionOccurred = true;
}
}
if (collisionOccurred)
{
mCollisionData.Add(collision);
}
}
public static bool BoxPlaneCollisionOccured(PSI_Collider_Box boxCol, PSI_Collider_Plane planeCol, out Vector3 point)
{
// Projecting the box vertices onto the plane. If a the vertex that is closest
// to the plane intersects it then the box and plane are colliding.
var boxVerts = boxCol.GetVertices();
float overlap = float.PositiveInfinity;
bool collisionOccured = false;
point = Vector3.zero;
for (int i = 0; i < boxVerts.Length; i++)
{
float distanceToPlane;
if (!planeCol.PosIsWithinPlaneBounds(boxVerts[i], out distanceToPlane))
{
continue;
}
if (distanceToPlane <= 0f && Mathf.Abs(distanceToPlane) < boxCol.pSize.magnitude)
{
collisionOccured = true;
if (distanceToPlane < overlap)
{
overlap = distanceToPlane;
}
}
}
if (collisionOccured)
{
// Resolve any overlap between the box and the plane.
ResolveCollisionOverlaps(boxCol, planeCol, -planeCol.pNormal.normalized, overlap);
// Getting the collision point by averaging the closest box verts to the plane.
boxVerts = boxCol.GetVertices();
int touchingVertexCount = 0;
for (int i = 0; i < boxVerts.Length; i++)
{
float distanceToPlane;
if (!planeCol.PosIsWithinPlaneBounds(boxVerts[i], out distanceToPlane))
{
continue;
}
if (distanceToPlane <= 0.01f)
{
point += boxVerts[i];
touchingVertexCount++;
}
}
point /= (float)touchingVertexCount;
// Calculate and apply the collision impulse to the box.
ApplyImpulses(boxCol, planeCol, -planeCol.pNormal.normalized, point);
// Apply friction to the box.
ApplyFriction(boxCol, planeCol, point);
return(true);
}
return(false);
}
