Plotting / erasing points on a circle

[Statsman1]

Hey everyone!

I hope you are all doing well. 

Here's the scenario...

Starting at the top of a circle and going counter-clockwise, I would like to...

Plot a filled dot at the top of the circle (using a radius of 1, then on an X-Y plane, center of circle at (0,0) that dot would be centered at (0,1)).

Determine at random how far along the circle the new dot will go, counter-clockwise.

Erase the previously drawn dot.

Plot the new dot.

Continue until the dot has passed through (-1,-1) and reached (0,-1).

Sort of like drawing a ball on a roulette wheel, but only one-half of a complete rotation, starting at the 12-o'clock position and going backwards to the 6-o'clock position.

I realize that the CIRCLE and PSET commands are in order here, and while I can determine the start and stop coordinates, I am having a heck of a time wrapping my head around the rest of it.  SIN and COS are long-forgotten trig functions, and I suspect I am using them to solve this...

Anybody have an idea here?

Thank you in advance!

Edited -

Using this...

Screen 12

Const Pi = 3.1415926

Circle (325, 225), 180, 6
Line (325, 225)-(x, y), 0

For j = 1 To 360
    Input "Enter value for point:"; s
    x = Int(Sin(s / 180 * Pi) * 180) + 325
    y = Int(Cos(s / 180 * Pi) * 180) + 225
    Line (325, 225)-(x, y), 15
Next j

- I bulldozed my way to learn that if s = 90, that code will draw a line from (0,0) to (1,0)

So, when s = 180, the result is a line from (0,0) to (0,1).  Yay.
And, when s = 0 or 360, the result is a line from (0,0) to (0,-1). Yay.

Accordingly, tomorrow, I have something to work on.  Any suggestions are welcome, but I think I figured out one route.

All the best, everyone!

[Pete]

Here's an idea. Post the code you have so far. Honestly, this sounds like some kind of a homework assignment, rather than a personal project, but I may be wrong. In any event, for homework, we encourage posting code and giving help at the point where a coder is stuck. If we post complete solutions, nothing is really leaned. You could also check out what others have done for similar circle related projects. The latest circle related thread is here: https://www.qb64.org/forum/index.php?topic=4189.0

Pete

[Statsman1]

Actually, I am 51 years old, and gave up homework a LONG time ago.

I am working on a particular game idea that is just to make myself happy, that’s all, not an assignment or anything. Just a racing program, and trying to get the cars around the curves is proving a challenge.

Hope this clarifies the requirements.

[Pete]

Ah, another youngster on the forum! Well, alrighty then....

So this depends a lot on if you will be requiring collision detection, in other words a player is driving the car, or if it is more of a simulation, where the car is just following the track.

Anyway, thank you for posting the code, and have a look t this: https://www.qb64.org/forum/index.php?topic=2710.msg119274#msg119274

It may give you some more ideas of how to work with circular movement.

Pete

[Pete]

Oh, and if you ever want to go linear: https://www.tapatalk.com/groups/qbasic/viewtopic.php?p=212867#p212867

[bplus]

Welcome @Statsman1

I modified your code a bits to help clarify circles and angles:

Code: QB64: [Select]

1. Screen 12
2.  
3. Const Pi = 3.1415926
4. Const Radius = 180
5. Const Xcenter = 325
6. Const Ycenter = 225
7. Do
8.     Cls
9.     Circle (Xcenter, 225), Radius, 6
10.     Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
11.     Input "Enter Degree Angle for point  > ", s
12.     RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
13.     x = Radius * Cos(RadianAngle) + Xcenter
14.     y = Radius * Sin(RadianAngle) + Ycenter
15.     Line (Xcenter, Ycenter)-(x, y), 15
16.     Locate 28, 40: Print "ZZZ...";
17.     Sleep
18. Loop Until _KeyDown(27) ' user presses escape
19.  

[bplus]

And here is a yellow square traveling that circle:

Code: QB64: [Select]

1. Screen 12
2.  
3. Const Pi = 3.1415926
4. Const Radius = 180
5. Const Xcenter = 325
6. Const Ycenter = 225
7. While _KeyDown(27) = 0
8.     Cls
9.     s = s + 1 ' increase 1 degree
10.     Circle (Xcenter, Ycenter), Radius, 6
11.     'Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
12.     'Input "Enter Degree Angle for point  > ", s
13.     RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
14.     x = Radius * Cos(RadianAngle) + Xcenter
15.     y = Radius * Sin(RadianAngle) + Ycenter
16.     Line (x - 5, y - 5)-Step(10, 10), 14, BF ' yellow square 10x10 at point x, y
17.     _Display ' stop flicker
18.     _Limit 60 ' loops per sec
19.     'Locate 28, 40: Print "ZZZ...";
20.     'Sleep
21. Wend '
22.  

[Pete]

Nice, Mark, but applying some of my mad SCREEN 0 skills, and once again, I wind up running circles around you...

Code: QB64: [Select]

1. SCREEN 12
2.  
3. CONST Pi = 3.1415926
4. CONST Radius = 180
5. CONST Xcenter = 325
6. CONST Ycenter = 225
7. WHILE _KEYDOWN(27) = 0
8.     CLS
9.     s = s + 1 ' increase 1 degree
10.     CIRCLE (Xcenter, Ycenter), Radius, 6
11.     LOCATE 14, 40: PRINT "YOU"
12.     'Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
13.     'Input "Enter Degree Angle for point  > ", s
14.     RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
15.     x = Radius * COS(RadianAngle) + Xcenter
16.     y = Radius * SIN(RadianAngle) + Ycenter
17.     LINE (x - 5, y - 5)-STEP(10, 10), 14, BF ' yellow square 10x10 at point x, y
18.     _DISPLAY ' stop flicker
19.     _LIMIT 60 ' loops per sec
20.     'Locate 28, 40: Print "ZZZ...";
21.     'Sleep
22. WEND '
23.  

[bplus]

I started a blue and white car:

Code: QB64: [Select]

1. Screen 12
2.  
3. Const Pi = 3.1415926
4. Const Radius = 180
5. Const Xcenter = 325
6. Const Ycenter = 225
7. While _KeyDown(27) = 0
8.     Cls
9.     s = s + 1 ' increase 1 degree
10.     Circle (Xcenter, Ycenter), Radius, 6
11.     'Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
12.     'Input "Enter Degree Angle for point  > ", s
13.     RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
14.     x = Radius * Cos(RadianAngle) + Xcenter
15.     y = Radius * Sin(RadianAngle) + Ycenter
16.     'Line (x - 5, y - 5)-Step(10, 10), 14, BF ' yellow square 10x10 at point x, y
17.     drawRect x, y, 20, 40, RadianAngle + _Pi / 2, 9
18.     drawRect x, y, 15, 15, RadianAngle + _Pi / 2, 15
19.     _Display ' stop flicker
20.     _Limit 60 ' loops per sec
21.     'Locate 28, 40: Print "ZZZ...";
22.     'Sleep
23. Wend '
24.  
25. Sub drawRect (x, y, w, h, raHeading, c As _Unsigned Long)
26.     ' from x,y draw midY h/2 towards raHeading
27.     x1 = x + h / 2 * Cos(raHeading)
28.     y1 = y + h / 2 * Sin(raHeading)
29.     x2 = x1 + w / 2 * Cos(raHeading + _Pi / 2)
30.     y2 = y1 + w / 2 * Sin(raHeading + _Pi / 2)
31.     x3 = x1 + w / 2 * Cos(raHeading - _Pi / 2)
32.     y3 = y1 + w / 2 * Sin(raHeading - _Pi / 2)
33.  
34.     x4 = x + h / 2 * Cos(raHeading - _Pi)
35.     y4 = y + h / 2 * Sin(raHeading - _Pi)
36.     x5 = x4 + w / 2 * Cos(raHeading + _Pi / 2)
37.     y5 = y4 + w / 2 * Sin(raHeading + _Pi / 2)
38.     x6 = x4 + w / 2 * Cos(raHeading - _Pi / 2)
39.     y6 = y4 + w / 2 * Sin(raHeading - _Pi / 2)
40.  
41.     Line (x2, y2)-(x3, y3), c
42.     Line (x3, y3)-(x6, y6), c
43.     Line (x6, y6)-(x5, y5), c
44.     Line (x5, y5)-(x2, y2), c
45.     Paint (x, y), c, c
46. End Sub
47.  
48.  

[bplus]

Pete's the red (of course) and yellow car ;-))

Code: QB64: [Select]

1. Screen 12
2.  
3. Const Pi = 3.1415926
4. Const Radius = 180
5. Const Xcenter = 325
6. Const Ycenter = 225
7. While _KeyDown(27) = 0
8.     Cls
9.     s = s + 2 ' increase 1 degree
10.     Circle (Xcenter, Ycenter), Radius, 6
11.     'Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
12.     'Input "Enter Degree Angle for point  > ", s
13.     RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
14.     x = Radius * Cos(RadianAngle) + Xcenter
15.     y = Radius * Sin(RadianAngle) + Ycenter
16.     'Line (x - 5, y - 5)-Step(10, 10), 14, BF ' yellow square 10x10 at point x, y
17.     drawRect x, y, 20, 40, RadianAngle + _Pi / 2, 9
18.     drawRect x, y, 15, 15, RadianAngle + _Pi / 2, 15
19.  
20.     p = p + 1
21.     RadianAngle = _D2R(p) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
22.     x = Radius * Cos(RadianAngle) + Xcenter
23.     y = Radius * Sin(RadianAngle) + Ycenter
24.     'Line (x - 5, y - 5)-Step(10, 10), 14, BF ' yellow square 10x10 at point x, y
25.     drawRect x, y, 20, 40, RadianAngle + _Pi / 2, 4
26.     drawRect x, y, 15, 15, RadianAngle + _Pi / 2, 14
27.  
28.     _Display ' stop flicker
29.     _Limit 60 ' loops per sec
30.     'Locate 28, 40: Print "ZZZ...";
31.     'Sleep
32. Wend '
33.  
34. Sub drawRect (x, y, w, h, raHeading, c As _Unsigned Long)
35.     ' from x,y draw midY h/2 towards raHeading
36.     x1 = x + h / 2 * Cos(raHeading)
37.     y1 = y + h / 2 * Sin(raHeading)
38.     x2 = x1 + w / 2 * Cos(raHeading + _Pi / 2)
39.     y2 = y1 + w / 2 * Sin(raHeading + _Pi / 2)
40.     x3 = x1 + w / 2 * Cos(raHeading - _Pi / 2)
41.     y3 = y1 + w / 2 * Sin(raHeading - _Pi / 2)
42.  
43.     x4 = x + h / 2 * Cos(raHeading - _Pi)
44.     y4 = y + h / 2 * Sin(raHeading - _Pi)
45.     x5 = x4 + w / 2 * Cos(raHeading + _Pi / 2)
46.     y5 = y4 + w / 2 * Sin(raHeading + _Pi / 2)
47.     x6 = x4 + w / 2 * Cos(raHeading - _Pi / 2)
48.     y6 = y4 + w / 2 * Sin(raHeading - _Pi / 2)
49.  
50.     Line (x2, y2)-(x3, y3), c
51.     Line (x3, y3)-(x6, y6), c
52.     Line (x6, y6)-(x5, y5), c
53.     Line (x5, y5)-(x2, y2), c
54.     Paint (x, y), c, c
55. End Sub
56.  
57.  

[Pete]

Ouch! My tailpipe hurts!

Well, it may be my car, but why is your wife driving?

Pete

[Statsman1]

You guys are awesome.  :)

Thank you so much for the help and the laughs, first thing in the morning.

[Cobalt]

Nice @bplus, now you just need 9 circles with smaller circles moving along and you can have a simulated Sol system! Add a yellow circle in the center for the sun and presto!

like so.. sorta

Code: QB64: [Select]

1. SCREEN 12
2.  
3. CONST Pi = 3.1415926
4. CONST Radius = 180
5. CONST Xcenter = 325
6. CONST Ycenter = 225
7. WHILE _KEYDOWN(27) = 0
8.  CLS
9.  s = s + 1 ' increase 1 degree
10.  CIRCLE (Xcenter, Ycenter), Radius, 6
11.  LOCATE 14, 40: PRINT "YOU"
12.  'Print "For Degrees: 0 = east, 90 = south, 180 = west, 270 = north"
13.  'Input "Enter Degree Angle for point  > ", s
14.  RadianAngle = _D2R(s) ' _D2R converts Degrees 2 (to) Radians which is what Sin and Cos process
15.  x = Radius * COS(RadianAngle) + Xcenter
16.  y = Radius * SIN(RadianAngle) + Ycenter
17.  'LINE (x - 5, y - 5)-STEP(10, 10), 14, BF ' yellow square 10x10 at point x, y
18.  'Earth.... well sorta
19.  CIRCLE (x, y), 10, 1 '_RGB32(12, 64, 224)
20.  PAINT (x - 2, y - 2), 1, 1
21.  PSET (x + 3, y + 3), 2: DRAW "ullurl3urulllur7duurl8ur9url10ur5drrurrullddllulul5ddululur"
22.  PSET (x + 3, y + 3), 2: DRAW "dr2ur3dldldlddldluurururu"
23.  _DISPLAY ' stop flicker
24.  _LIMIT 60 ' loops per sec
25.  'Locate 28, 40: Print "ZZZ...";
26.  'Sleep
27. WEND '
28.  
29.  

[bplus]

Nice @bplus, now you just need 9 circles with smaller circles moving along and you can have a simulated Sol system! Add a yellow circle in the center for the sun and presto!

Halfway there:

Code: QB64: [Select]

1. _Title "Checkout Which Planet Closet to Earth Most of the Time" 'B+ mod started 2019-03-25
2. ' inspired by david_uwi post: https://www.qb64.org/forum/index.php?topic=1184.0
3.  
4. Const xmax = 700
5. Const ymax = 700
6. Const CX = 350
7. Const CY = 350
8. Screen _NewImage(xmax, ymax, 32)
9. _ScreenMove 300, 0
10.  
11. Type planetType
12.     x As Single '             track position after so many Earth Days
13.     y As Single
14.     name As String '          data
15.     radius As Single '        millions of KM  data
16.     edy As Single '           earth day year data
17.     oneDayAngle As Single '   calc 2 * PI / edy
18.     distFromEarth As Single ' calc when run model
19.     closest As Integer '      calc when run model
20.     cum As Single '           calc when run model
21. End Type
22.  
23. 'load planet data from Internet
24. Dim planet(1 To 4) As planetType
25. For i = 1 To 4
26.     Read planet(i).name
27.     Read planet(i).radius
28.     Read planet(i).edy
29.     planet(i).oneDayAngle = _Pi(2 / planet(i).edy)
30. Next
31. 'review data check load
32. For i = 1 To 4
33.     Print planet(i).name; " is "; planet(i).radius; " million KM from sun and covers an radian angle of"; planet(i).oneDayAngle; " in one Earth day."
34. Next
35. Input "<Enter> Model of Solar System", wate$
36.  
37. 'run model
38. For days = 1 To 365.26 * 1000
39.  
40.     For i = 1 To 4
41.         planet(i).x = CX + planet(i).radius * Cos(planet(i).oneDayAngle * days)
42.         planet(i).y = CY + planet(i).radius * Sin(planet(i).oneDayAngle * days)
43.     Next
44.     For i = 1 To 4
45.         planet(i).distFromEarth = Sqr((planet(i).x - planet(3).x) ^ 2 + (planet(i).y - planet(3).y) ^ 2)
46.         planet(i).cum = planet(i).cum + planet(i).distFromEarth
47.     Next
48.  
49.     If planet(1).distFromEarth < planet(2).distFromEarth And planet(1).distFromEarth < planet(4).distFromEarth Then planet(1).closest = planet(1).closest + 1
50.     If planet(2).distFromEarth < planet(1).distFromEarth And planet(2).distFromEarth < planet(4).distFromEarth Then planet(2).closest = planet(2).closest + 1
51.     If planet(4).distFromEarth < planet(1).distFromEarth And planet(4).distFromEarth < planet(2).distFromEarth Then planet(4).closest = planet(4).closest + 1
52.  
53.     'display
54.     Cls
55.     Print "Days:"; days
56.  
57.     Print "average distances ", "Mercury", "Venus", "Mars"
58.     Print Space$(22); planet(1).cum / days, planet(2).cum / days, planet(4).cum / days
59.  
60.     Print "fraction of time closest", "Mercury", "Venus ", "Mars"
61.     Print Space$(22), planet(1).closest / days, planet(2).closest / days, planet(4).closest / days
62.     Circle (CX, CY), 6, _RGB32(255, 255, 0)
63.     For i = 1 To 4
64.         Circle (planet(i).x, planet(i).y), i, &HFFFFFFFF
65.         Select Case i
66.             Case 1: c~& = &HFFFF0000
67.             Case 2: c~& = &HFF00FFFF
68.             Case 3: c~& = &HFF0000AA
69.             Case 4: c~& = &HFFAA6600
70.         End Select
71.         Paint (planet(i).x, planet(i).y), c~&, &HFFFFFFFF
72.     Next
73.     _Display
74.     _Limit 30
75.  
76. Next
77.  
78. Data "Mercury",57.9,87.97
79. Data "Venus",108.2,224.7
80. Data "Earth",149.6,365.26
81. Data "Mars",227.9,686.98
82.  
83.  

[Cobalt]

Halfway there:

Nice.

though why is Mars bigger than Earth?