Navigation Utilities Implementation

Navigation provides a number of different modes. Within each mode you can have the ability to do terrain following and/or collision avoidance. For collision avoidance and terrain following, we will refer you to the tutorial on the main site as the process is described there. The one footnote to add is that we use the geometry intersection tools from this library.

The terrain following is based on a generalised collision detection system. As we have to build a completely generalised system we cannot use more specialised code. In fact, we recommend that if you can build a specialised scenegraph for your application that it will be more efficient than this code.

Code Outline

Class Structure

Freeform Navigation

Viewpoint Management

Determining Frame Delay Amounts

The goal is to increase frame-rate as much as possible on a Canvas3D. The main question is when should I ask a Canvas3D to render a new frame?

• If too early it just can not do the job, because it has not finished the previous one yet.
• If I ask it too late, then I loose important milliseconds and it just sits around lazy.

First guess would be:

long approximateTimeForNextFrameDuration= view.getLastFrameDuration();

My first navigation module worked with this iterating algorithm. Then I got tired of it and decided to find the function that is the most closest to the iterating algorithm's result, so I might even gain more performance with not doing the iteration, but loose some timing accuracy.

Just think of it! If you turn around in a scene and in a corner of the room there is a messy heavy object, but the other end is empty (You should see my flat!), then the iterating algorithm really has a job to do and some frames will not be shot with the best possible timing until the algorithm settles.

The function that fitted the best was this:

timerDelay = 10 + (int)view.getLastFrameDuration() / 2;

WHY /2.0 ???
WHY +10 ???

I do not understand this function, but it gave me the best results ever.

Then I tested it with different video cards and platforms and operating systems. They all gave the same results. Actually the value 10 could be smaller for faster PCs, but 10 worked for all and 10ms is not much.

Other References

• QOTA Algorithm for fast terrain following.
• Lazlo Seregi's Navigation implementation notes