[Visualpython-users] rate() function

[Gary S. <st...@nm...>]

Hi all,

This might be a bit off-topic--perhaps hardware related(?)--but does
anyone know exactly what happens when you pick value of N such that your
computer can't handle a given "rate(N)" visualpython statement? Do frames
get dropped? Or is it dependent on one's graphics card, or screen refresh
rates, or openGL implementation? Using the program below, my _actual_
framerate increases as a stair-stepped function of the _specified_
framerate. What I find odd is that the _actual_ framerate does keep on
increasing. That is, rate(50) doesn't give me a 50Hz frame rate, but
(according to my loop anyway) using rate(100) gives me a better than 50Hz
frame rate. I would think that the actual framerate should increase
linearly to the point where one's computer is maxed out, and then plateau
indefinitely. Apparently that's naive. Any ideas? I've tested this on both
a couple machines (though both are portables with, of course, LCD
monitors). 

Thanks in advance for any guesses (or better yet, answers) ...

Gary
strang-@at@-nmr.mgh.harvard.edu

--- cut here ---

from visual import *
import time, sys, whrandom

scene.title = "Speed test"
# Create 2 frames
fworld = frame(pos=(0,0,0))
ftarget = frame(frame=fworld,pos=(0,0,0))
ftarget.pos = (0,0,0)
fworld.pos = (0,0,10)

# Draw some main objects
body = cylinder(frame=ftarget, pos=(0,0,0), axis=(0,0,0.35), radius=1, color=(0,0,1),visible=1)
pin = cylinder(frame=ftarget, pos=(0,1,0), axis=(0,1,0), radius=1, color=(1,1,1),visible=1)
pinball = sphere(frame=ftarget, pos=(0,-1,0), radius=1, color=(1,1,0),visible=1)
topbox = box(frame=ftarget, pos=(0,0.34,0.20), axis=(0,1,0), length=0.2,width=0.1,height=0.1, color=(1,0,0),visible=1)
horizon = cylinder(frame=ftarget, pos=(-5,2,0), axis=(10,0,0), radius=1, color=(0,1,0),visible=1)

xINC = 0
yINC = 0.001
zINC = 0.003
rollINC = 0
pitchINC = 0
yawINC = 0
scene.autoscale = 0
NUM_DOTS    = 500
RADIUS  = 120
rad = 0.4
# now draw background objects
for i in range(0, NUM_DOTS):
    x = whrandom.random() - 0.5
    y = whrandom.random() - 0.5
    z = whrandom.random() - 0.5
    length = math.sqrt(x*x + y*y + z*z)
    x = x / length * RADIUS
    y = y / length * RADIUS + 1.8
    z = z / length * RADIUS
    sphere(pos=(x,y,z),radius=rad)

frameratelist = []
for framerate in range(10,250,1):
    framecount = 0
    starttime = time.clock()
    while framecount<5*framerate:  # integrate over, theoretically, 5sec
        rate(framerate)
        framecount += 1
        fworld.pos.x -= xINC
        fworld.pos.y -= yINC
        fworld.pos.z = framecount*zINC

        # Rotate "CAMERA" (actually, move whole _world_ around camera)
        fworld.rotate(angle=pitchINC, axis=(1,0,0), origin=scene.mouse.camera)
        fworld.rotate(angle=yawINC, axis=(0,1,0), origin=scene.mouse.camera)
        fworld.rotate(angle=rollINC, axis=(0,0,1), origin=scene.mouse.camera)
    endtime = time.clock()
    print "Rate(%i): %i frames in %2.2f sec = %2.2f frames/sec" % (framerate, framecount, (endtime-starttime), framecount/(endtime-starttime))
    frameratelist.append((framerate, framecount, (endtime-starttime), framecount/(endtime-starttime)))