Tracking question

Support Basics & Interface
#1

I think this is a simple one:

Can someone explain the principles involved in getting a camera (or other object) to predictably track something else? Sometimes it works fine, others, when I do ctrl-t<old track, it points off in the wrong direction. I worked through this in a tutorial somewhere recently, but the tut never really explained the underlying principle of the remedy for non-tracking, and therefore I never really learned it. Something to do with clearing origin or applying size and rotation, I think. Since often nothing visible happens with these commands, I really don’t understand when they’re needed and what they do…Anyway, after lots of clearing of origins and applying rotations, my darn camera still points the wrong way…

Thank you.

#2

I think that Blender assumes the constraint was applied from the start and that if the camera has been moved or rotated since it was added, then these translations are applied “after the fact” when you track or parent it. So, if a normal track would result in the camera rotating 90deg to the right then if the camera was already rotated 90deg right beforehand, it will point 180deg instead.

In essence, the translation is applied to the object’s original location, rotation etc… That’s why clearing these fixes the misalignment.

Of course we don’t always realise that something is rotated because we may not physically rotate it. But how an object is added to a scene (particularly which ortho view was active) makes a difference to its rotation.

Actually, that’s all my assumption. It’s always bugged me too but after seeing your question, I suddenly felt I had an answer - so thanks for asking :slight_smile: