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