initial commit, 4.5 stable

thirdparty/jolt_physics/Jolt/Geometry/RaySphere.h

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+// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
+// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <Jolt/Math/FindRoot.h>
+
+JPH_NAMESPACE_BEGIN
+
+/// Tests a ray starting at inRayOrigin and extending infinitely in inRayDirection against a sphere,
+/// @return FLT_MAX if there is no intersection, otherwise the fraction along the ray.
+/// @param inRayOrigin Ray origin. If the ray starts inside the sphere, the returned fraction will be 0.
+/// @param inRayDirection Ray direction. Does not need to be normalized.
+/// @param inSphereCenter Position of the center of the sphere
+/// @param inSphereRadius Radius of the sphere
+JPH_INLINE float RaySphere(Vec3Arg inRayOrigin, Vec3Arg inRayDirection, Vec3Arg inSphereCenter, float inSphereRadius)
+{
+	// Solve: |RayOrigin + fraction * RayDirection - SphereCenter|^2 = SphereRadius^2 for fraction
+	Vec3 center_origin = inRayOrigin - inSphereCenter;
+	float a = inRayDirection.LengthSq();
+	float b = 2.0f * inRayDirection.Dot(center_origin);
+	float c = center_origin.LengthSq() - inSphereRadius * inSphereRadius;
+	float fraction1, fraction2;
+	if (FindRoot(a, b, c, fraction1, fraction2) == 0)
+		return c <= 0.0f? 0.0f : FLT_MAX; // Return if origin is inside the sphere
+
+	// Sort so that the smallest is first
+	if (fraction1 > fraction2)
+		std::swap(fraction1, fraction2);
+
+	// Test solution with lowest fraction, this will be the ray entering the sphere
+	if (fraction1 >= 0.0f)
+		return fraction1; // Sphere is before the ray start
+
+	// Test solution with highest fraction, this will be the ray leaving the sphere
+	if (fraction2 >= 0.0f)
+		return 0.0f; // We start inside the sphere
+
+	// No solution
+	return FLT_MAX;
+}
+
+/// Tests a ray starting at inRayOrigin and extending infinitely in inRayDirection against a sphere.
+/// Outputs entry and exit points (outMinFraction and outMaxFraction) along the ray (which could be negative if the hit point is before the start of the ray).
+/// @param inRayOrigin Ray origin. If the ray starts inside the sphere, the returned fraction will be 0.
+/// @param inRayDirection Ray direction. Does not need to be normalized.
+/// @param inSphereCenter Position of the center of the sphere.
+/// @param inSphereRadius Radius of the sphere.
+/// @param outMinFraction Returned lowest intersection fraction
+/// @param outMaxFraction Returned highest intersection fraction
+/// @return The amount of intersections with the sphere.
+/// If 1 intersection is returned outMinFraction will be equal to outMaxFraction
+JPH_INLINE int RaySphere(Vec3Arg inRayOrigin, Vec3Arg inRayDirection, Vec3Arg inSphereCenter, float inSphereRadius, float &outMinFraction, float &outMaxFraction)
+{
+	// Solve: |RayOrigin + fraction * RayDirection - SphereCenter|^2 = SphereRadius^2 for fraction
+	Vec3 center_origin = inRayOrigin - inSphereCenter;
+	float a = inRayDirection.LengthSq();
+	float b = 2.0f * inRayDirection.Dot(center_origin);
+	float c = center_origin.LengthSq() - inSphereRadius * inSphereRadius;
+	float fraction1, fraction2;
+	switch (FindRoot(a, b, c, fraction1, fraction2))
+	{
+	case 0:
+		if (c <= 0.0f)
+		{
+			// Origin inside sphere
+			outMinFraction = outMaxFraction = 0.0f;
+			return 1;
+		}
+		else
+		{
+			// Origin outside of the sphere
+			return 0;
+		}
+		break;
+
+	case 1:
+		// Ray is touching the sphere
+		outMinFraction = outMaxFraction = fraction1;
+		return 1;
+
+	default:
+		// Ray enters and exits the sphere
+
+		// Sort so that the smallest is first
+		if (fraction1 > fraction2)
+			std::swap(fraction1, fraction2);
+
+		outMinFraction = fraction1;
+		outMaxFraction = fraction2;
+		return 2;
+	}
+}
+
+JPH_NAMESPACE_END