https://stackoverflow.com/questions/52339320/unity-shader-hlsl-equivalent-of-vector3-projectonplane
a 在 b 上的投影

感觉向量还是这样写好看


mathmatica

Dot[{1，0} , {-1，0}]    // 点乘   是一个数
{1，0} x {-1，0}			// 叉乘   是一个向量

// If your plane normal vector is normalized:inline float3 projectOnPlane( float3 vec, float3 normal )
{return vec - normal * dot( vec, normal );
}
// If it's not:inline float3 projectOnPlane( float3 vec, float3 normal )
{return vec - normal * ( dot( vec, normal ) / dot( normal, normal ) );
}
// Same formula, depending on GPU model & driver version can be either faster or slower:inline float3 projectOnPlane( float3 v, float3 n )
{float3 r;r.x = n.y * n.y * v.x + n.z * n.z * v.x - n.x * n.y * v.y - n.x * n.z * v.z;r.y = n.x * n.x * v.y - n.x * n.y * v.x - n.y * n.z * v.z + n.z * n.z * v.y;r.z = n.x * n.x * v.z - n.x * n.z * v.x + n.y * n.y * v.z - n.y * n.z * v.y;return r / dot(n, n);
}