Shaker/Veldrid/Agg/VectorMath/PlaneFloat.cs

/*
Copyright (c) 2014, Lars Brubaker
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*/

namespace MatterHackers.VectorMath
{
	public class PlaneFloat
	{
		public float DistanceFromOrigin { get; private set; }
		public Vector3Float Normal { get; private set; }
		private const float TreatAsZero = .000001f;
		public PlaneFloat(Vector3Float planeNormal, float distanceFromOrigin)
		{
			this.Normal = planeNormal.GetNormal();
			this.DistanceFromOrigin = distanceFromOrigin;
		}

		public PlaneFloat(Vector3Float point0, Vector3Float point1, Vector3Float point2)
		{
			this.Normal = (point1 - point0).Cross((point2 - point0)).GetNormal();
			this.DistanceFromOrigin = Normal.Dot(point0);
		}

		public float GetDistanceFromPlane(Vector3Float positionToCheck)
		{
			float distanceToPointFromOrigin = positionToCheck.Dot(Normal);
			return distanceToPointFromOrigin - DistanceFromOrigin;
		}

		public float GetDistanceToIntersection(Ray ray, out bool inFront)
		{
			inFront = false;
			float normalDotRayDirection = Normal.Dot(new Vector3Float(ray.directionNormal));
			if (normalDotRayDirection < TreatAsZero && normalDotRayDirection > -TreatAsZero) // the ray is parallel to the plane
			{
				return float.PositiveInfinity;
			}

			if (normalDotRayDirection < 0)
			{
				inFront = true;
			}

			return (DistanceFromOrigin - Normal.Dot(new Vector3Float(ray.origin))) / normalDotRayDirection;
		}

		public float GetDistanceToIntersection(Vector3Float pointOnLine, Vector3Float lineDirection)
		{
			float normalDotRayDirection = Normal.Dot(lineDirection);
			if (normalDotRayDirection < TreatAsZero && normalDotRayDirection > -TreatAsZero) // the ray is parallel to the plane
			{
				return float.PositiveInfinity;
			}

			float planeNormalDotPointOnLine = Normal.Dot(pointOnLine);
			return (DistanceFromOrigin - planeNormalDotPointOnLine) / normalDotRayDirection;
		}

		public bool RayHitPlane(Ray ray, out float distanceToHit, out bool hitFrontOfPlane)
		{
			distanceToHit = float.PositiveInfinity;
			hitFrontOfPlane = false;

			float normalDotRayDirection = Normal.Dot(new Vector3Float(ray.directionNormal));
			if (normalDotRayDirection < TreatAsZero && normalDotRayDirection > -TreatAsZero) // the ray is parallel to the plane
			{
				return false;
			}

			if (normalDotRayDirection < 0)
			{
				hitFrontOfPlane = true;
			}

			float distanceToRayOriginFromOrigin = Normal.Dot(new Vector3Float(ray.origin));

			float distanceToPlaneFromRayOrigin = DistanceFromOrigin - distanceToRayOriginFromOrigin;

			bool originInFrontOfPlane = distanceToPlaneFromRayOrigin < 0;

			bool originAndHitAreOnSameSide = originInFrontOfPlane == hitFrontOfPlane;
			if (!originAndHitAreOnSameSide)
			{
				return false;
			}

			distanceToHit = distanceToPlaneFromRayOrigin / normalDotRayDirection;
			return true;
		}
	}
}