Arcball like 3D figure rotation

Example that shows how to add arcball control to a 3D window

Description

One of the major drawbacks of matlab is the lack of a way of changing the viewpoint of a 3D mesh using a natural (arcball) interaction.

In this simple function I demonstrate the arcball interaction allowing a 3D sphere to be moved naturally. Run the function and drag and drop with your mouse on the sphere surface.

A very important aspect that you should note is that I am rotating the ACTUAL 3D object instead of the viewpoint.

There is a specific reason for this choice. The OpenGL lighting is linked to the axis in matlab, thus, if you rotate the veiwpoint, the lighting on the mesh surface wouldn't change. On the other hand, if you rotate your object using hgttransoforms you achieve this result.

It is now apparently bug-free :)

• MATLAB release: MATLAB 7.6 (R2008a)

[Noone U. Noh]

The cause of your "bug" is likely that at each step you rotate the object that was rotated in the last step. Each rotation introduces a little bit of round-off errors that are being magnified by doing it a zillion times. Instead, you should always make the rotations with respect to the original (unrotated) object.

[Noone U. Noh2]

Actually that is not true. If you check, the rotation is applied to the model which is "saved" in M_previous in the moment the first mouse click take place. That doesn't change anymore during dragging.

[Andrea Tagliasacchi]

Thanks for the observation anyway. I took a look at the code again and even though Noh2 observation was correct, there was a similar bug. The "rotation direction" was embedded in model space using the inverse of the current rotation matrix (taken from graphic context) and not the one of the original model.

I will upload the final version.
There was also a vector normalization missing that might have caused other issues.

[P G]

The sphere example proposed in the code does not work with Matlab 7.0.0.19920 (R14) and 7.0.4.352 (R14). There may be a problem between surf objects and hgtransform. It works properly with mesh and surface objects. Great work, thanks.