Coplanarity Test for Any Quantity of 3D Points - Epic Wiki
# Coplanarity Test for Any Quantity of 3D Points
# Contents
# Overview
Dear Community,
It took me a long time to create and test a fully accurate function for determining if an arbitrary number of FVectors / 3D points are coplanar!
Here is the function I came up with for your entertainment!
# Code
static FORCEINLINE bool CoPlanar(const TArray<FVector>& Points, const float Tolerance = 0.1) { //less than 4 points = coplanar if(Points.Num() < 4) return true; //Get the Normal for plane determined by first 3 points const FVector Normal = FVector::CrossProduct(Points[2] - Points[0], Points[1] - Points[0]); const int32 Total = Points.Num(); for(int32 v = 3; v < Total; v++) { //Abs of PointPlaneDist, dist should be 0 if(FMath::Abs( FVector::PointPlaneDist(Points[v], Points[0], Normal)) > Tolerance) return false; } return true; }
# Explanation
Any 3 points determine a plane, so I obtain the normal of the plane determined by the first 3 points!
const FVector Normal = FVector::CrossProduct(Points[2] - Points[0], Points[1] - Points[0]);
Now that I've established the plane I want to test against, I compare all the other points using UE4's PointPlaneDist function.
if(FMath::Abs( FVector::PointPlaneDist(Points[v], Points[0], Normal)) > Tolerance)
I am allowing an error tolerance rather than demanding exactly 0.
# PointPlaneDist
Vector.h /** * Calculate the signed distance (in the direction of the normal) between * a point and a plane. * * @param Point The Point we are checking. * @param PlaneBase The Base Point in the plane. * @param PlaneNormal The Normal of the plane. * * @return Signed distance between point and plane. */ static float PointPlaneDist( const FVector &Point, const FVector &PlaneBase, const FVector &PlaneNormal );
# Abs
The absolute value is essential!
if(FMath::Abs( FVector::PointPlaneDist(...
# Conclusion
Enjoy!
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