Download or view derbytrack2.frink in plain text format
/** This program renders a track for womens' flat-track roller derby.
Main rules page:
http://wftda.com/rules
Appendix B specifies track layout process:
http://wftda.com/rules/wftda-rules-appendix-b-track-design.pdf
Note that the inner boundary is symmetrical about the x and y axes, but
the outer boundary is not. The entry to the curves is 2 feet narrower than
the exits to the curves.
*/
use geometry.frink
use Derby.frink
//input["press enter"]
g = new graphics
g.color[.5,.5,.5]
p = new filledGeneralPath
// Draw inside ring
p.moveTo[12.5, -17.5]
p.lineTo[12.5, 17.5]
p.circularArc[0, 17.5, -180 degrees]
p.lineTo[-12.5, -17.5]
p.circularArc[0, -17.5, -180 degrees]
p.close[]
// Draw outside ring (in opposite winding direction.)
p.moveTo[25.5, -17.5]
p.circularArc[-1, -17.5, 180 degrees]
p.lineTo[-25.5, 17.5]
p.circularArc[1, 17.5, 180 degrees]
p.close[]
g.add[p]
g.color[1, .4, .4, .7]
g.stroke[3/12]
y = -17.5
xo = 25.5
// The track narrows by 2 feet along the direction of travel in straightaways,
// which are 35 feet long.
sideslope = 35/2
// Draw lines on right side. First is pivot line
for n = 1 to 4
{
g.line[12.5, y, xo, y]
y = y + 10
xo = xo + 10 / sideslope
}
// Draw lines on left side.
y = 17.5
xo = -25.5
for n = 1 to 4
{
g.line[-12.5, y, xo, y]
y = y - 10
xo = xo - 10 / sideslope
}
// Draw lines in curves
rin = 12.5
rout1 = 25.5
rout2 = 27.5
c = (7 feet + 1/2 in) / feet
// Center of the inner ring
cx = 0
cy = -17.5
// Center of the outer ring, which is offset from the inner ring.
cx1 = -1
cy1 = -17.5
r1 = 26.5
for n = 1 to 5
{
theta = 2 n arcsin[c/(2 rin)] // Translate the chord to angle.
x1 = rin cos[theta] + cx
y1 = cy - rin sin[theta]
sols = circleLineIntersections[cx, cy, x1, y1, cx1, cy1, r1]
g.line[ x1, y1, sols@1@0, sols@1@1]
g.line[-x1, -y1, -sols@1@0, -sols@1@1]
}
/** This program draws and tests the roller derby coordinate system defined
in Derby.frink. */
black = new color[0,0,0]
blue = new color[0,0,1]
gray = new color[0,0,0,.5]
for d = 0 to Derby.d4 step 1 // This gives one entire loop of the track
{
// Inside of track (w=0)
g.color[black]
[x,y] = Derby.WDtoXY[0,d]
g.fillEllipseCenter[x,y,.5,.5]
// Outside of track (w=1)
[x,y] = Derby.WDtoXY[1,d]
g.fillEllipseCenter[x,y,.5,.5]
// Middle of track (w = 0.5)
g.color[gray]
[x,y] = Derby.WDtoXY[0.5,d]
g.fillEllipseCenter[x,y,.5,.5]
// Effective track length (w = Derby.effectiveW)
g.color[blue]
[x,y] = Derby.WDtoXY[Derby.effectiveW, d]
g.fillEllipseCenter[x,y,.5,.5]
}
/* Draw 10-foot lines all the way around the track.
Note that the jammer line is at d=5 so we start there. */
for d=5 to Derby.d4+5 step 10
{
[x1,y1] = Derby.WDtoXY[0, d]
[x2,y2] = Derby.WDtoXY[1, d]
g.line[x1, y1, x2, y2]
}
// Redraw the jammer line and pivot line in red.
g.color[1,0,0,.8]
// Jammer line is w=[0,1], d=5.
[x1,y1] = Derby.WDtoXY[0,5]
[x2,y2] = Derby.WDtoXY[1,5]
g.line[x1,y1,x2,y2]
// Pivot line is w=[0,1], d=35.
[x1,y1] = Derby.WDtoXY[0,35]
[x2,y2] = Derby.WDtoXY[1,35]
g.line[x1,y1,x2,y2]1
//g.show[]
//g.write["derbytrack.html", 800, 800]
//browse["derbytrack.html"]
g2 = new graphics
win = g2.show[800,600,1]
lastTime = now[]
startW = 0.5
startD = 4
vx = 0 ft /s
vy = 0 ft/s
lastvx = vx
lastvy = vy
trackDistance = randomFloat[10,40]
[lastX, lastY] = Derby.WDtoXY[startW, startD]
nominalDelay = 1/30 s
for d = startD to 4 Derby.d4 + 6 step 1/2
{
g2 = new graphics
/*g2.saveTransform[]
g2.translate[60,0]
g2.scale[1/2,1/2]
g2.add[g]
g2.restoreTransform[]*/
g2.add[g]
w = 0.5 + .4 sin[d/trackDistance]
[x,y] = Derby.WDtoXY[w, d]
// Hey let's be nerds and calculate actual physical velocities of our sim
// time = now[]
// delay = time - lastTime
// lastTime = time
dx = (x-lastX) feet
dy = (y-lastY) feet
trackAngle = arctan[dy,dx]
// Draw the skater
g2.saveTransform[]
g2.rotate[trackAngle,x,y]
g2.color[1,1,0,.9]
g2.fillRectCenter[x, y, 2, 2]
g2.restoreTransform[]
distance = sqrt[dx^2 + dy^2] // Distance traveled this timestep
speed = distance/nominalDelay
vx = dx / nominalDelay
vy = dy / nominalDelay
dvx = (vx - lastvx) / nominalDelay
dvy = (vy - lastvy) / nominalDelay
// Calculate acceleration and lean angle.
a = sqrt[dvx^2 + dvy^2]
angle = arctan[a/gee]
// println[angle]
// println[speed]
// println[a]
g2.saveTransform[]
g2.translate[4,0]
g2.color[black]
g2.line[0,10,4 sin[angle], 10 - 4 cos[angle]]
g2.restoreTransform[]
g2.font["Monospaced", 3]
g2.text[padLeft[format[speed, "mph", 2], 9, " "], 0, 0]
g2.text[padLeft[format[a, "gee", 2], 9, " "], 0, 3]
// g2.text[padLeft[format[vx, "mph", 2], 9, " "], 0, 6]
// g2.text[padLeft[format[vy, "mph", 2], 9, " "], 0, 9]
// g2.text[padLeft[format[dvx, "gee", 2], 9, " "], 0, 6]
lastX = x
lastY = y
lastvx = vx
lastvy = vy
win.replaceGraphics[g2]
sleep[nominalDelay]
}
//g2.write["track.svg",400,800]
//g2.write["track.html",400,800]
Download or view derbytrack2.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen, eliasen@mindspring.com