Moving (X,Y) in a Circular Path

[SirCrow]

Using the following code, I get a nice, perfect circle drawn (the real goal is to move points in a circular path, of course):

Code: QB64: [Select]

1. SCREEN 12
2.  
3. CX = 320: CY = 240 'Centre of circle
4. Rad = 120 'Radius
5.  
6. 'FOR Ang = 0 TO 359
7. FOR Ang = 0 TO 6.28 STEP 1 / 360
8.     _LIMIT 240 ':CLS
9.  
10.     X = CX + COS(Ang) * Rad
11.     Y = CY + SIN(Ang) * Rad
12.  
13.     PSET (X, Y)
14.     LOCATE 11, 10: PRINT USING "Angle: ###.###"; Ang:
15.  
16. NEXT
17.  

But my problem is that, in my game, my angles run from 0 to 359, or similar.
How can I adapt the code to work with the very different numbers?  Thanks!
(NOTE: The above code won't actually be used as-is in my prog.;  I'm merely trying to gain an understanding of this here stuff.)

Joe

[FellippeHeitor]

COS() and SIN() expect radians instead of angles, so you can use _D2R to convert from Degrees to Radians:

Code: QB64: [Select]

1. SCREEN 12
2.  
3. CX = 320: CY = 240 'Centre of circle
4. Rad = 120 'Radius
5.  
6. 'FOR Ang = 0 TO 359
7. FOR Ang = 0 TO 360 STEP .1
8.     _LIMIT 240 ':CLS
9.  
10.     X = CX + COS(_D2R(Ang)) * Rad
11.     Y = CY + SIN(_D2R(Ang)) * Rad
12.  
13.     PSET (X, Y)
14.     LOCATE 11, 10: PRINT USING "Angle: ###.###"; Ang:
15.  
16. NEXT
17.  

The added STEP .1 is so that the circle doesn't have leak areas.

[SirCrow]

COS() and SIN() expect radians instead of angles, so you can use _D2R to convert from Degrees to Radians:
. . .

Thanks, Fellippe.  I did not know about _D2R and the others.  I was thinking about dividing by 57.3 or something like that, but I might've known there was already something quick and easy available.

[FellippeHeitor]

All it does is value * 0.01745329251994329576923690768489

[codeguy]

There's a better way to make a leakproof circle than using a constant to determine the number of steps. 2pi*radius gives you the minimum number of steps necessary to generate a circle that does not leak when painted or flood-filled, although there are faster methods than both of these to do this.

[SirCrow]

There's a better way to make a leakproof circle than using a constant to determine the number of steps. 2pi*radius gives you the minimum number of steps necessary to generate a circle that does not leak when painted or flood-filled, although there are faster methods than both of these to do this.

That sounds as if it would work when radians are used;  I'm working with degrees.

In any case, my real objective is not to draw a leakproof circle, but simply to move objects in a circular path around another object.
For years and years I'd wondered how others did it, and now I'm finally starting to understand it myself.

[bplus]

To move in spiral around a point do the same as circle only change the radius with the angle for the x, y points. Spiral out by adding to radius and spiral in by subtracting from radius.

[SirCrow]

To move in spiral around a point do the same as circle only change the radius with the angle for the x, y points. Spiral out by adding to radius and spiral in by subtracting from radius.

Being curious, I had already tried it, but I got unpredictable results.  I'll be playing around with that in the future.  Thanks.

[bplus]

Code: QB64: [Select]

1. SCREEN 12
2.  
3. CX = 320: CY = 240 'Centre of circle
4. Rad = 1 'Radius
5.  
6. 'FOR Ang = 0 TO 359
7. FOR Ang = 0 TO 360 * 8 'spin around 8 times
8.     _LIMIT 200 ':CLS
9.     Rad = Rad + .1
10.     X = CX + COS(_D2R(Ang)) * Rad
11.     Y = CY + SIN(_D2R(Ang)) * Rad
12.  
13.     PSET (X, Y)
14.     LOCATE 11, 10: PRINT USING "Angle: ###,###.###"; Ang:
15.  
16. NEXT
17.  
18.  

[SirCrow]

I don't understand why it's OK for Ang to to past 360, but the result is pretty cool.

[SMcNeill]

I don't understand why it's OK for Ang to to past 360, but the result is pretty cool.

Spin 360 degrees... You’ve made a complete circle.

Now spin 720 degrees.   You’ve rotated in place twice, making 2 circles...

1080 degrees....  3 complete rotations...

[Pete]

I don't understand why it's OK for Ang to to past 360, but the result is pretty cool.

Spin 360 degrees... You’ve made a complete circle.

Now spin 720 degrees.   You’ve rotated in place twice, making 2 circles...

1080 degrees....  3 complete rotations...

To go further will require a new keyword... _CONGRESS

It is pretty amazing how powerful this stuff can be in gaming / graphics. I just ran Mark's "Boing" code today and frankly, I did not expect such good quality with so few lines of code. Good luck Joe with your game, too.

Pete

[SirCrow]

It is pretty amazing how powerful this stuff can be in gaming / graphics. I just ran Mark's "Boing" code today and frankly, I did not expect such good quality with so few lines of code. Good luck Joe with your game, too.

Pete

Thanks very much.