Matrix multiplication issue

Processing Coding Questions
3

Hello,

Use only radians!

TAU radians is equal to 360 deg
TWO_PI is equal to 360 deg.

https://processing.org/reference/TAU.html

To get you started try this in your existing code:

float angle = TAU/360; 
boolean state = false;

  if (state)
    {
    for (int i=0; i<points.length; i++) points[i]=pos(points[i]);
    state = false;
    }

void keyPressed()
  {
  //if (key == 'd') angle += +TAU/360;
  //if (key == 'a') angle -= -TAU/360;
  state = true;
  }

void keyReleased()
  {
  state = false;
  }

Changing the angle in your keyPressed will have no effect in your code because you defined this array at the start of your code:

float angle = 10;

float[][] rotationXY = {
  {cos(angle), -sin(angle)}, 
  {sin(angle), cos(angle)}
  };

The angle variable won’t change after that! Try calling the function in draw.

I leave the rest with you.

:)