Array rotation

Post reply

❤Follow Topic(5)

1 favourites

2 posts

From the Asset Store

Array Editor

$5 USD

Supports 1D, 2D, 3D arrays. Import and export arrays in JSON format

paradine

- Fakero
- - Joined 21 Jan, 2015
  - 7 topics • 15 posts
- 1
- 11 Nov, 2019
- Quote
Hello! Please help with array rotation. 90 degrees clockwise for example.

The first image is the original array. The second is an array after turning clockwise.

How can i do this?
Try Construct 3

Develop games in your browser. Powerful, performant & highly capable.
Try Now Construct 3 users don't see these ads
- R0J0hound
- - Joined 15 Jun, 2009
  - 90 topics • 7,088 posts
- 2
- 11 Nov, 2019
- Quote
If the array is square you can set another array of the same size to be a rotated version. Here's a simplified version.

for CW 90 degrees
array1: for each xy -- array2: set at (array1.width-1-array1.curY, array1.curX) to array1.curValue

for CCW 90 degrees

array1: for each xy -- array2: set at (array1.curY, array1.width-1-array1.curX) to array1.curValue

Long version on how that's derived

2d rotation is defined by these formulas:

newX = (x-centerX)*cos(angle)-(y-centerY)*sin(angle) +centerX newY = (x-centerX)*sin(angle)+(y-centerY)*cos(angle) +centerY

Then we can simplify things when using say 90 degrees for the angle since cos(90)=0 and sin(90)=1.

newX = -(y-centerY)+centerX newY = (x-centerX)+centerY

Then we can simplify further since the array is square so centerX=centerY, and centerX = (array.width-1)/2. Plug that into the formulas and we get:

newX = -y+array.width-1 newY = x

Using similar logic you could do rotation of non square arrays, you'd just have to flip the x and y sizes of the second array.

I suppose you could do something clever to rotate an array in place, but I think it's much simpler to just save the rotation on something else and then copy it back to the original if needed.