Real-time Motion and Drawing Speed
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Speed is one of the most important aspects of a cave survey program. The faster the program can display the cave, the easier it will be for you to scan through the passages and select a particular portion of the cave for viewing. Also, being able to manipulate the cave rapidly allows you to see aspects of the structure and geology that would be invisible otherwise. Speed is also extremely important when you are working with large caves. The current version of the COMPASS Viewer is highly optimized for high-speed drawing. It is as much as 20 times faster than previous versions.
Real-time Motion. If your computer is fast enough and the cave isn't too big, the Viewer will allow you to rotate and move through the cave in real-time. With real-time motion you can pan, zoom and rotate smoothly with no jerks or pauses, like watching a movie. To do real-time motion, set the Viewer for Hidden Refresh mode, use small Increments and use the auto repeat buttons. It is also useful to use the 3D Compass and the Drag Mode Option to manipulate the cave with mouse.
Gauging Speed. The Viewer displays the drawing speed of the current image on the Status Line. The drawing speed is displayed in Frames Per Second (FPS.) The more frames per second that the program can display, the faster the real-time motion. For true real-time motion, you need about 5 FPS. Frame rates lower than 5 FPS will appear jerky, but will still be quite useable.
Preformance. The ability to do real-time motion depends on many factors. Here is a detailed discussion of the factors that effect performance:
1. Computer CPU speed. Your computer’s CPU speed is the primary factor effecting the Viewer’s drawing speed. Current model computers with a fast video card can draw almost any cave with real-time motion. For example, current PC’s can draw all 110 miles (180 km.) of Lechuguilla Cave at about 30 frames per second.
To give you an idea of the correlation between CPU speed and drawing speed, here is chart showing the drawing speed for the 110 miles (180 km.) of Lechuguilla Cave. (Note: Lechuguilla Cave is growing about as fast as the Viewer has speeded up.)
2. Video Card. The type of video card you have in your system can make a real difference in the drawing speed. The best video cards use what is called “hardware acceleration” where the video card actually performs part of the work that is normally performed by the CPU. Since there is constant competition between companies, the best video changes from month to month. To find the best performing video card, refer to magazine and internet reviews.
3. Cave Size. Obviously, the more passage in a cave, the longer it takes to draw the image.
4. Zooming. As you increase the magnification and zoom in on part of the cave, large sections of the image may be outside of the window. The Viewer has a special feature that allows it to skip over parts of the cave that are outside the window. This will dramatically increase the drawing speed.
5. Drawing Mode. The Viewer has many drawing modes and depending on how much work need to be done, the drawing speed can vary a great deal. The fastest mode is the basic, single-color mode with no special features enabled. It has been specially optimized for speed. For example, it is about three times faster than the color-by-depth modes.
The Stereo Mode has also been highly optimized. This is because, in Stereo Mode, the program must draw two complete images of the cave. As result, even though it is highly optimized, it is about half as fast as the single-color mode. All other modes are slower. Modes that draw the passage walls and other complex features can be much slower.
6. Video Mode. Most video cards have several different operating modes. These modes can effect the drawing speed. For example, some older video cards run slower if you use higher resolution or more colors. However, most modern video cards have hardware acceleration, which allows them to use high-resolution and high-color modes without any speed penalty. Depending on the type of video card you have, it may be worthwhile to experiment with the resolution and the number of colors in your display.
7. Processor Types. Different CPU’s have different capabilities and these capabilities can effect the drawing speed of the Viewer. For example, all 386’s and some 486’s didn’t have a floating-point math co-processor. Since the Viewer makes extensive use of floating-point operations, these processors could slow the drawing speed dramatically. Since most people are using Pentium or Athalon processors, this is not usually a problem. However, for best performance, you should be using a Pentium or 586 level computer.