Re: Intersection of FlatFields


The only way I've done this is illustracted in the visad.python.JPythonMethods.find() method that returns an integer array of sampling indecies where the condition specified is met. For example:
        int[] k = find(x, "gt", y)
Although it uses a visad Data subtract between the two Data's - which takes care of any resampling needed, it then loops through that to determine if the "condition" is it's probably not going to help you too much.

Regarding direct manipulations: it makes sense that the fewer pixels that need to be re-drawn on the screen (such as when the scene is smaller) the faster it will happen. In the old AWT days (which of course we still use!) we would redraw only a portion of the 'background image' when we moved something along on top of it. Someone else will have to comment on what goes on in the Java3D world, though.


Kevin Manross wrote:


I am trying to optimize my code a bit. I have two FlatFields of the same type (range->height) which produce two curves on the same display.

(Please see the right panel of:

I want to obtain all the ranges where the smooth curve lies below the jagged curve. Currently, I am looping through the range points, obtaining the values for each curve (smooth, jagged) at each point and determine which is greater (saving those range points where the jagged curve is greater than the smooth curve), and moving on to the next range point.

This works sufficiently, but 1) depending on the resolution I want (low = 400, high = 1600) along the range, I am making that many comparisons each time I move the red line on the left panel. 2) To calculate for the entire circle on the left panel (720 red lines), that means I am making between 288,000 and 1,152,000 comparisons. On my machine (1.2 GHz CPU, 1 Gb RAM) this takes about 40 seconds to do.

Is there a better way to find the intersection of two FlatFields?

On another performance topic, I have noticed that the smaller I shrink my VisAD displays, the more responsive the DirectManipulationRenderers are, and vice versa. I believe this is a somewhat common behavior that deals with rendering as I have seen similar retardation with expanding an .mpg or video game. Is this slowness vs. size tradeoff just something to live with, or is there a way that I can speed things up?

Many thanks to those who have responded to my questions. I keep hoping that I will become proficient enough to return the favor. ;-)


Tom Whittaker
University of Wisconsin-Madison

  • 2003 messages navigation, sorted by:
    1. Thread
    2. Subject
    3. Author
    4. Date
    5. ↑ Table Of Contents
  • Search the visad archives: