Moving/translating a set of points on a spline.

Math and Physics Programming

Started by Spa8nky July 10, 2010 03:11 PM

2 comments, last by haegarr 13 years, 9 months ago

Spa8nky

230

Author

July 10, 2010 03:11 PM

If I have a spline that is defined as follows:

        private List<Vector3> controlPoints;            // List of control points for the spline         private ushort[] indices;        private List<Vector3> interpolatedPoints;       // List of interpolated points located on the spline

how should I translate those points should I want the spline to move?

Should I move all the points once each time the spline is moved:

        public void Translate(Vector3 movementVector)        {            for (int i = 0; i < interpolatedPoints.Count; ++i)            {                interpolatedPoints += movementVector;                if (i < controlPoints.Count)                {                    controlPoints += movementVector;                }            }        }

Or should I use a transformation matrix?

Which one would you be inclined to use, and why?

quasar3d

814

July 10, 2010 06:11 PM

If you only want to do a translation, then do it this way. There's no point in using a matrix (which will use many more operations), when a simpler way will work just as well.

Spa8nky

230

Author

July 11, 2010 03:55 AM

Indeed. I was also avoiding the transformation matrix as I would need to store a collection of transformed points if I were to go with this method.

This is because I will require the world space coordinates of each point for calculations and there would be no point transforming each point each time a specific point is required.

Unless someone has a better suggestion?

haegarr

7,408

July 11, 2010 05:41 AM

It depends on how interpolatedPoints is related to the spline. Transforming both at once means that both a coupled tightly. I assume that interpolatedPoints are used for rendering, so that the graphical representation and the mathematical basis are coupled here!?

However, this part of the code

            for (int i = 0; i < interpolatedPoints.Count; ++i)            {                interpolatedPoints += movementVector;                if (i < controlPoints.Count)                {                    controlPoints += movementVector;                }            }

seems me inefficient and error-prone. It is inefficient because there is a chance that the continous program flow will be disrupted unneccessarily, and there is the chance that too little controlPoints get updated (although some unshown constraints may prevent that). It seems me better to use

            for (int i = 0; i < interpolatedPoints.Count; ++i)            {                interpolatedPoints += movementVector;            }            for (int i = 0; i < controlPoints.Count; ++i)            {                controlPoints += movementVector;            }

instead.

Moving/translating a set of points on a spline.

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Moving/translating a set of points on a spline.

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines