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I'm learning at coding so i have tons of questions... so i will use this thread to try to find help. Thanks in advance!

I'm trying to make a new game and i need that a 1-block 8x8 sprite moves tracing a circular path.

Any help?

Thanks & sorry for my bad english

P#29800 2016-10-01 13:08 ( Edited 2016-10-17 14:55)

I feel your pain...while I'm not new a coding, Pico8 was the first time in a long time that I've need to actually program something - no helpers, no plugins, just good old fashioned programming.

And that means math...which I've had to learn slowly to make the games I want. It's been a long, slow road for me but as I've been learning formulas and making functions, every game gets a little easier and cooler.

That being said...here's what I use to have a object/sprite rotate around a single point in a circle. It's not really "tracing" a path...I'm sure there's a way but I'm not smart enough to figure that out. But this snippet will get your sprite to rotate/orbit around a point at a given speed and distance from the center.

--"planet" that a moon will go around

--moon that rotates around the planet
    speed=.006, --speed of rotation
    ang=0 --starting angle of rotationcle (0=right,.25=up,.5=left,.75=down)

function _update()

    moon.x = cos(moon.ang)*planet.rad+planet.x;
    moon.y = sin(moon.ang)*planet.rad+planet.y;

function _draw()
    circ(planet.x,planet.y,planet.rad,5) --just a reference
    print("\140",moon.x,moon.y,10) --draw your sprite here
P#29801 2016-10-01 13:31 ( Edited 2016-10-01 17:31)

Wow great! It works like a charm.

PD: Maths.... I wish they had told me that mathematics are
essential for videogames XDDD I had paid more attention back in school

P#29812 2016-10-01 17:58 ( Edited 2016-10-01 21:58)

I can add to this.

Math is VERY essential ! Highly essential. Critically essential.

That and the ability to extrapolate data or interpret what might be easily understood to a person - to write it out where a computer can also understand and do it.

If you want to be master of this PICO language, I suggest you read every little bit of the "pico-8.txt" included with your purchased PICO language.

For extra credit, you can go here and get some good ideas on coding too.


You might challenge yourself with a few sample codes.

[1] Write code that moves a sprite left, right, up, and down when you hit any of the 4-arrow keys.
[2] Write code to bounce a ball around on the screen. The edges reflect it.
[3] Write code to play some simple music you write.


[4] Generate a simple tiled map and scroll it from right to left.

P#29818 2016-10-01 23:31 ( Edited 2016-10-02 03:31)

Another maths problem...

Sprite A wants to go to where sprite B is tracing a fluid diagonal... not a irregular one like in the gif.
I want a smooth diagonal...

Any sugestions?

P#30741 2016-10-12 11:18 ( Edited 2016-10-12 15:18)

You and me both, Hokutoy. I have need of a diagonal tracing array. I wrote one years ago. I don't need it just yet, but one tool I'm working on will REQUIRE it - not just for cosmetic display.

P#30744 2016-10-12 11:33 ( Edited 2016-10-12 15:33)

@Hokutoy, regarding diagonal movement: The atan2 function is what you're looking for. Use it to get an angle to a destination, then use the sin and cos functions to turn that angle into y and x components.

Here's a method in my current project that does this:

function movetowardspoint(actor, destx, desty)
    if actor.z > 0 then return end
    local dx = actor.x - destx
    local dy = actor.y - desty
    local distp = sqrt(abs(dx)^2 + abs(dy)^2)

    if distp > 4 then
        local o = atan2(dx, dy)
        local pvx = cos(o) * actor.dv
        local pvy = sin(o) * actor.dv
        actor.vx -= pvx
        actor.vy -= pvy
        if dx > 4 then           
            actor.flipsprite = true
        elseif dx < -4 then
            actor.flipsprite = false
P#30754 2016-10-12 12:38 ( Edited 2016-10-12 16:38)

Wow thanks. It works very well.

P#30762 2016-10-12 14:11 ( Edited 2016-10-12 18:11)

Well now Fweez, that's a real brainweave. I seem to remember figuring out years ago by trial and error a way to draw from any point to any point using simple floating point math - no need for Sin(), Cos(), Atan2(), or Sqrt().

I think I wrote it in QBasic somewheres around here ... Ah ! There it is. Converting.

Cart #30785 | 2016-10-12 | Code ▽ | Embed ▽ | No License

32-lines, 137 tokens. Floating point calculations only.

-- draw line between two random
-- points w/o complex formulas
-- by dw817



-- ^ pick random coordinates

a=abs(x1-x2) b=abs(y1-y2)
if a>b then
  b=b/a a=1
  a=a/b b=1


  if x1<x2 then x1+=a else x1-=a end
  if y1<y2 then y1+=b else y1-=b end
until abs(x1-x2)<1 and abs(y1-y2)<1
goto again
P#30786 2016-10-12 18:31 ( Edited 2016-10-12 22:54)

Hokutoy, did you ever get your cart posted ? Did you understand how mine works without using SIN(), COS(), or SQRT() ?

P#31095 2016-10-16 23:57 ( Edited 2016-10-17 03:58)

Yes dw817 it'a a nice aproach!
My cart is not posted or finished... too many real life things at the moment... i need some free time for coding :\

And the ::again:: --> flip() goto again is something new for me so it was great to know it!


P#31106 2016-10-17 09:19 ( Edited 2016-10-17 13:19)

Hi, Hokutoy:

If you're not knowing.

FLIP() slows down your program and tries to prevent against and flickering. It's not as good as FLIP() for some other languages I've used as graphics can and will spill through if there are a lot of them.

Best to use FLIP() at parts in your code where you do want to show what updates to the screen you've made at that time.

GOTO uses double colon "::" front and back labels. GOTO is a marvelous command. With it, you can exit any loop, no matter how tight and GO TO where you need to.

Here's hoping you find time for your cart - I really like the initial animation you posted and it appears you have some kind of mathematical numbers game in mind.

Definite interest there ! :)

P#31108 2016-10-17 10:55 ( Edited 2016-10-17 14:55)

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