Function GenerateMatrixUsingVector

Sources/EERIE/EERIEmath.cpp:1175–1230

}

void GenerateMatrixUsingVector(EERIEMATRIX * matrix, const EERIE_3D * vect, const float rollDegrees)
{
	// Get our direction vector (the Z vector component of the matrix)
	// and make sure it's normalized into a unit vector
	EERIE_3D zAxis;
	memcpy(&zAxis, vect, sizeof(EERIE_3D));
	TRUEVector_Normalize(&zAxis);

	// Build the Y vector of the matrix (handle the degenerate case
	// in the way that 3DS does) -- This is not the TRUE vector, only
	// a reference vector.
	EERIE_3D yAxis;

	if (!zAxis.x && !zAxis.z)
		Vinit(&yAxis, -zAxis.y, 0.f, 0.f);
	else
		Vinit(&yAxis, 0.f, 1.f, 0.f);

	// Build the X axis vector based on the two existing vectors
	EERIE_3D xAxis;
	Vcross(&xAxis, &yAxis, &zAxis);
	TRUEVector_Normalize(&xAxis);

	// Correct the Y reference vector
	Vcross(&yAxis, &xAxis, &zAxis);
	TRUEVector_Normalize(&yAxis);
	yAxis.x = -yAxis.x;
	yAxis.y = -yAxis.y;
	yAxis.z = -yAxis.z;

	// Generate rotation matrix without roll included
	EERIEMATRIX rot, roll;
	MatrixReset(&rot);
	MatrixReset(&roll);
	rot._11 = yAxis.x;
	rot._12 = yAxis.y;
	rot._13 = yAxis.z;
	rot._21 = zAxis.x;
	rot._22 = zAxis.y;
	rot._23 = zAxis.z;
	rot._31 = xAxis.x;
	rot._32 = xAxis.y;
	rot._33 = xAxis.z;

	// Generate the Z rotation matrix for roll
	roll._33 = 1.f;
	roll._44 = 1.f;
	roll._11 = EEcos(DEG2RAD(rollDegrees));
	roll._12 = -EEsin(DEG2RAD(rollDegrees));
	roll._21 = EEsin(DEG2RAD(rollDegrees));
	roll._22 = EEcos(DEG2RAD(rollDegrees));

	// Concatinate them for a complete rotation matrix that includes
	// all rotations
	MatrixMultiply(matrix, &rot, &roll);
}