C++ ofVec3f::dot方法代码示例

// Make a rotation Quat which will rotate vec1 to vec2
// Generally take adot product to get the angle between these
// and then use a cross product to get the rotation axis
// Watch out for the two special cases of when the vectors
// are co-incident or opposite in direction.
void ofQuaternion::makeRotate_original( const ofVec3f& from, const ofVec3f& to ) {
	const float epsilon = 0.0000001f;

	float length1  = from.length();
	float length2  = to.length();

	// dot product vec1*vec2
	float cosangle = from.dot(to) / (length1 * length2);

	if ( fabs(cosangle - 1) < epsilon ) {
		//osg::notify(osg::INFO)<<"*** Quat::makeRotate(from,to) with near co-linear vectors, epsilon= "<<fabs(cosangle-1)<<std::endl;

		// cosangle is close to 1, so the vectors are close to being coincident
		// Need to generate an angle of zero with any vector we like
		// We'll choose (1,0,0)
		makeRotate( 0.0, 0.0, 0.0, 1.0 );
	} else
		if ( fabs(cosangle + 1.0) < epsilon ) {
			// vectors are close to being opposite, so will need to find a
			// vector orthongonal to from to rotate about.
			ofVec3f tmp;
			if (fabs(from.x) < fabs(from.y))
				if (fabs(from.x) < fabs(from.z)) tmp.set(1.0, 0.0, 0.0); // use x axis.
				else tmp.set(0.0, 0.0, 1.0);
			else if (fabs(from.y) < fabs(from.z)) tmp.set(0.0, 1.0, 0.0);
			else tmp.set(0.0, 0.0, 1.0);

			ofVec3f fromd(from.x, from.y, from.z);

			// find orthogonal axis.
			ofVec3f axis(fromd.getCrossed(tmp));
			axis.normalize();

			_v[0] = axis[0]; // sin of half angle of PI is 1.0.
			_v[1] = axis[1]; // sin of half angle of PI is 1.0.
			_v[2] = axis[2]; // sin of half angle of PI is 1.0.
			_v[3] = 0; // cos of half angle of PI is zero.

		} else {
			// This is the usual situation - take a cross-product of vec1 and vec2
			// and that is the axis around which to rotate.
			ofVec3f axis(from.getCrossed(to));
			float angle = acos( cosangle );
			makeRotate( angle, axis );
		}
}

void findCoordinateSystem(vector<ofVec3f> &input,ofVec3f &origin,ofVec3f &xVec,ofVec3f &yVec) {
    origin = input[0];
    xVec = (input[1]-input[0]).getNormalized();
    float proj = xVec.dot(input[3]-input[0]);
    yVec = (input[3]-(input[0]+xVec*proj)).getNormalized();
}