C++ float3::Cross方法代码示例

Quat MUST_USE_RESULT Quat::RotateFromTo(const float3 &sourceDirection, const float3 &targetDirection)
{
	assume(sourceDirection.IsNormalized());
	assume(targetDirection.IsNormalized());
	float angle = sourceDirection.AngleBetweenNorm(targetDirection);
	assume(angle >= 0.f);
	// If sourceDirection == targetDirection, the cross product comes out zero, and normalization would fail. In that case, pick an arbitrary axis.
	float3 axis = sourceDirection.Cross(targetDirection);
	float oldLength = axis.Normalize();
	if (oldLength == 0)
		axis = float3(1, 0, 0);
	return Quat(axis, angle);
}

/** Calculates the intersection between a line and a triangle. The facing is not accounted for, so
	rays are reported to intersect triangles that are both front and backfacing.
	According to "T. Möller, B. Trumbore. Fast, Minimum Storage Ray/Triangle Intersection. 2005."
	http://jgt.akpeters.com/papers/MollerTrumbore97/
	@param linePos The starting point of the line.
	@param lineDir The direction vector of the line. This does not need to be normalized.
	@param v0 Vertex 0 of the triangle.
	@param v1 Vertex 1 of the triangle.
	@param v2 Vertex 2 of the triangle.
	@param u [out] The barycentric u coordinate is returned here if an intersection occurred.
	@param v [out] The barycentric v coordinate is returned here if an intersection occurred.
	@return The distance along the ray to the point of intersection, or +inf if no intersection occurred.
		If no intersection, then u and v and t will contain undefined values. If lineDir was not normalized, then to get the
		real world-space distance, one must scale the returned value with lineDir.Length(). If the returned value is negative,
		then the intersection occurs 'behind' the line starting position, with respect to the direction vector lineDir. */
float Triangle::IntersectLineTri(const float3 &linePos, const float3 &lineDir,
		const float3 &v0, const float3 &v1, const float3 &v2,
		float &u, float &v)
{
	float3 vE1, vE2;
	float3 vT, vP, vQ;

	const float epsilon = 1e-4f;

	// Edge vectors
	vE1 = v1 - v0;
	vE2 = v2 - v0;

	// begin calculating determinant - also used to calculate U parameter
	vP = lineDir.Cross(vE2);

	// If det < 0, intersecting backfacing tri, > 0, intersecting frontfacing tri, 0, parallel to plane.
	const float det = vE1.Dot(vP);

	// If determinant is near zero, ray lies in plane of triangle.
	if (fabs(det) <= epsilon)
		return FLOAT_INF;
	const float recipDet = 1.f / det;

	// Calculate distance from v0 to ray origin
	vT = linePos - v0;

	// Output barycentric u
	u = vT.Dot(vP) * recipDet;
	if (u < -epsilon || u > 1.f + epsilon)
		return FLOAT_INF; // Barycentric U is outside the triangle - early out.

	// Prepare to test V parameter
	vQ = vT.Cross(vE1);

	// Output barycentric v
	v = lineDir.Dot(vQ) * recipDet;
	if (v < -epsilon || u + v > 1.f + epsilon) // Barycentric V or the combination of U and V are outside the triangle - no intersection.
		return FLOAT_INF;

	// Barycentric u and v are in limits, the ray intersects the triangle.
	
	// Output signed distance from ray to triangle.
	return vE2.Dot(vQ) * recipDet;
//	return (det < 0.f) ? IntersectBackface : IntersectFrontface;
}

Quat MUST_USE_RESULT Quat::RotateFromTo(const float3 &sourceDirection, const float3 &targetDirection)
{
	assume(sourceDirection.IsNormalized());
	assume(targetDirection.IsNormalized());
	// If sourceDirection == targetDirection, the cross product comes out zero, and normalization would fail. In that case, pick an arbitrary axis.
	float3 axis = sourceDirection.Cross(targetDirection);
	float oldLength = axis.Normalize();
	if (oldLength != 0.f)
	{
		float halfCosAngle = 0.5f*sourceDirection.Dot(targetDirection);
		float cosHalfAngle = Sqrt(0.5f + halfCosAngle);
		float sinHalfAngle = Sqrt(0.5f - halfCosAngle);
		return Quat(axis.x * sinHalfAngle, axis.y * sinHalfAngle, axis.z * sinHalfAngle, cosHalfAngle);
	}
	else
		return Quat(1.f, 0.f, 0.f, 0.f);

}

float MUST_USE_RESULT float3::ScalarTripleProduct(const float3 &u, const float3 &v, const float3 &w)
{
	return u.Cross(v).Dot(w);
}