Re: [Visualpython-users] basic questions

[Bruce S. <Bru...@nc...>]

VPython implements a second "rendering" thread which about 25 times per second 
interrupts your computations to create a 3D image (using OpenGL) from the 
current attributes of the objects, and the current (mouse-determined) "camera" 
viewing angle. A complete rendering is done each time (25 per second) even if no 
object has changed nor the camera has moved. For this reason performance with 
very large numbers of objects is likely to be poor, but it's easy enough to test 
simply by creating a very large number of objects. You could make the window 
invisible while computing, so as not to be interrupted by rendering, but once 
you make the window visible you may see poor performance for zooming and rotating.

The cheapest object to render is "points" which makes 2D disks or squares 
positioned at 3D locations. It is moreover an array object, with a list for the 
positions of the points.

Please say more about your question regarding zoom and rotate. What is "wild" 
about using the mouse to rotate or zoom the camera for looking at the scene?

There is documentation on mouse manipulations in the Visual help available on 
the Help menu in IDLE. Under Windows, Events, & Files see Mouse Events. Also, in 
the contributed section of vpython.org are some example programs that do fancy 
things with the mouse. And see the Tutorial on the first page of the help for 
the basics on using the mouse to zoom and rotate.

Bruce Sherwood

Tim Smith (25121) wrote:
> 1.      Can vpython handle large datasets? I’m considering using it for 
> a project modelling a large geographical body, I might need to plot 
> 1,000,000 points or more.
> 
> 2.      What would be the best object to use ?
> 
> 3.      Is there a tutorial on mouse manipulation so I can zoom in and 
> out and rotate my object? The default behaviour seems a bit wild