# Plotting 3D data

1. Dec 9, 2007

### r4nd0m

I have a set of 3D data (i.e. a large file where each row contains three spatial coordinates) and I'd like to get a nice, smooth 3D object out of it. The objects are not surfaces, so it's not just plotting a function (i.e. to every (x,y) there exists more than one z).

Does anyone have an idea which (freeware) application can deal with this kind of stuff? Thanks in advance.

2. Dec 9, 2007

### robphy

Are you merely looking to effectively plot "pixels" or "voxels"?
To get something "smooth" out of a collection of points, you probably have to provide some kind of interpolation scheme.

3. Dec 9, 2007

### r4nd0m

Well, let's say I have some 1000 points which form (or should form) a ball, for example. What I want to get is a nice, smooth 3D ball. Is that possible?

4. Dec 9, 2007

### robphy

You can try to run it through some kind of averaging scheme.
You could do a surface fit to a sphere to determine the center and radius.

5. Dec 9, 2007

### r4nd0m

yeah, but those objects are pretty crazy and really far away from spheres.
what kind of averaging schemes do you mean?

6. Dec 9, 2007

### robphy

What "objects" are you talking about?
Didn't you just ask about a ball (whose surface is a sphere)?

Here are some examples of interpolation:
http://en.wikipedia.org/wiki/Interpolation

7. Dec 9, 2007

### r4nd0m

The ball was just an example. The objects that I'm working with are much complicated.

I'm not really sure if interpolation is what I'm searching for.

8. Dec 9, 2007

### robphy

How many points are you talking about?
For a simple platform to get a first look at the data,
try http://www.vpython.org
to plot pixels (as boxes) in 3-D.

9. Dec 9, 2007

### r4nd0m

It's about 30x30x30 points, more or less.

10. Dec 9, 2007

### robphy

First try my suggestion above.
If your points describe a surface, you could try some algorithm that triangulates it [which guesses how the sampled-points are possibly connected], then another algorithm that tries to find a smooth approximation of it... to be rendered on a finer grid.

11. Sep 21, 2009

### tuathan

hi,
i want to plot a set of 3-D data.
i have 3 spatial co-ordinates (x, y, z) and then a physical quantity i have measured.
Is there a straight forward free plotting package i could use to plot this data?

thanks!