RayTriangle8.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/Vec8.h>
 
JPH_NAMESPACE_BEGIN
 
JPH_INLINE Vec8 RayTriangle8(Vec3Arg inOrigin, Vec3Arg inDirection, Vec8Arg inV0X, Vec8Arg inV0Y, Vec8Arg inV0Z, Vec8Arg inV1X, Vec8Arg inV1Y, Vec8Arg inV1Z, Vec8Arg inV2X, Vec8Arg inV2Y, Vec8Arg inV2Z)
{
    // Epsilon
    Vec8 epsilon = Vec8::sReplicate(1.0e-12f);
 
    // Zero & one
    Vec8 zero = Vec8::sZero();
    Vec8 one = Vec8::sReplicate(1.0f);
 
    // Find vectors for two edges sharing inV0
    Vec8 e1x = inV1X - inV0X;
    Vec8 e1y = inV1Y - inV0Y;
    Vec8 e1z = inV1Z - inV0Z;
    Vec8 e2x = inV2X - inV0X;
    Vec8 e2y = inV2Y - inV0Y;
    Vec8 e2z = inV2Z - inV0Z;
 
    // Get direction vector components
    Vec8 dx = Vec8::sSplatX(Vec4(inDirection));
    Vec8 dy = Vec8::sSplatY(Vec4(inDirection));
    Vec8 dz = Vec8::sSplatZ(Vec4(inDirection));
 
    // Begin calculating determinant - also used to calculate u parameter
    Vec8 px = dy * e2z - dz * e2y;
    Vec8 py = dz * e2x - dx * e2z;
    Vec8 pz = dx * e2y - dy * e2x;
    
    // if determinant is near zero, ray lies in plane of triangle
    Vec8 det = e1x * px + e1y * py + e1z * pz;
 
    // Check which determinants are near zero
    UVec8 det_near_zero = Vec8::sLess(det.Abs(), epsilon);
 
    // Set components of the determinant to 1 that are near zero to avoid dividing by zero
    det = Vec8::sSelect(det, Vec8::sReplicate(1.0f), det_near_zero);
 
    // Calculate distance from inV0 to ray origin
    Vec8 sx = Vec8::sSplatX(Vec4(inOrigin)) - inV0X;
    Vec8 sy = Vec8::sSplatY(Vec4(inOrigin)) - inV0Y;
    Vec8 sz = Vec8::sSplatZ(Vec4(inOrigin)) - inV0Z;
 
    // Calculate u parameter and flip sign if determinant was negative
    Vec8 u = (sx * px + sy * py + sz * pz) / det;
 
    // Prepare to test v parameter
    Vec8 qx = sy * e1z - sz * e1y;
    Vec8 qy = sz * e1x - sx * e1z;
    Vec8 qz = sx * e1y - sy * e1x;
                    
    // Calculate v parameter and flip sign if determinant was negative
    Vec8 v = (dx * qx + dy * qy + dz * qz) / det;
 
    // Get intersection point and flip sign if determinant was negative
    Vec8 t = (e2x * qx + e2y * qy + e2z * qz) / det;
 
    // Check if there is an intersection
    UVec8 no_intersection = 
        UVec8::sOr
        (
            UVec8::sOr
            (
                UVec8::sOr
                (
                    det_near_zero, 
                    Vec8::sLess(u, zero)
                ),
                UVec8::sOr
                (
                    Vec8::sLess(v, zero), 
                    Vec8::sGreater(u + v, one)
                )
            ), 
            Vec8::sLess(t, zero)
        );
 
    // Select intersection point or FLT_MAX based on if there is an intersection or not
    return Vec8::sSelect(t, Vec8::sReplicate(FLT_MAX), no_intersection);
}
 
JPH_NAMESPACE_END