Stacked rings mapping

Patterns and Code
1

Hi all. How would I map rings that are stacked on top of each other? I have 7 identical rings that I want to stack on top of each other, but I don’t quite know how to map it

2 
function (pixelCount) {
  var ringSize = 16
  var map = [];
  for (i = 0; i < pixelCount; i++) {
    c = i / pixelCount * Math.PI * 2 * (pixelCount/ringSize)
    map.push([Math.cos(c), Math.sin(c), Math.floor((i)/ringSize)])
  }
  return map
}

I believe this will do what you’re looking for. As long as your pixelCount is a multiple of your ringSize.

1 Like
3

The above code sets the z value equal to i (which changes 0 to pixelCount-1) divided by ringsize

This means z varies, in slow spiral upward.
Let’s say ringsize is 16
from 0, 1/16, 2/16,3/16 etc. So it’s a small rise.
At 16/16, it’s 1, and so on…

This gets renormalized, but the end result is still a spiral rise from the bottom.

This is more a long string of lights than flat rings.
For rings, flatten that math, by rounding down.

So use floor() on it. Then only the whole number is used, so it’s zero, zero, zero, then one, one, one, etc

Edit: the code has floor correctly. My brain didn’t see it. But hopefully the above is clear why floor(i/ringsize) works.

4

I hear what you’re saying but not sure how to implement your suggestion :confused:

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5

I’m not seeing where another floor is needed. But I also don’t quite understand how the mapper works so I’m assuming I’m missing something.

If I just mentally go through the function, I get z as only whole integers.

For i = 0, z = floor(0/16) = 0
For i = 1, z = floor(1/16) = 0
For i = 17, z = floor(17/16) = 1
For i = 18, z = floor (18/16) = 1

I do see why it needs to be floor((i+1)/ringSize), though.

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6

Sigh, I’m a goof and misread it as not having a floor the first time. Never mind. I glanced at the code and if I’d bothered to cut and paste, I’d have seen it had the floor already. My bad.

But it doesn’t need to be i+1, that’ll shift it wrong, ring 1 would 0-15, so pixel 16 would be ring 2… Etc.

7

I swear, 90% of my programming problems are trying to compensate for 0-indexed things when I don’t need to.

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8

We all do it… 90% of all programming is debugging the mistakes you make.

9

Have you heard this one?

There’s only two hard things in computer science:

  • Naming things
  • Cache invalidation
  • Off-by-one errors
5 Likes
10

There’s only 10 kinds of programmers; those who think in binary and those who don’t.

2 Likes
11

Question what does “i” mean in the code? Is it Index?

12

This is where it comes from, yes it represents a pixel index indirectly.

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