cureently stuck in axis rotation

noob123

I am extremely new to processing and am currently trying to get a cube to mimic the rotation of an ADXL335 accelerometer. I have the code for Arduino sending the angle in degrees to processing and the cube responding . however the cube isn't responding the way I need it to. when rotating the accelerometer the cube rotate differently to my movement. ( when splitting up the axis the x axis mimics fine until I add the y or z axis)

here is my code for processing

import processing.serial.*;
Serial myPort;  
String SerialBuffer;
Float X = 0.0;
Float Y = 0.0;
Float Z = 0.0;
float[] degs;

void setup()
{
size(500,500,P3D);
myPort = new Serial(this,"COM15",4800); 
myPort.bufferUntil('\n');
delay(1000);
}
void serialEvent (Serial myPort)
{
  SerialBuffer = myPort.readString();
  degs = float(split(SerialBuffer, ','));
  println(" working = " + SerialBuffer + degs[1]); //print it out in the console
  X=degs[0];
  Y=degs[1];
  Z=degs[2];
}
void draw()
{
  background(255);
  stroke(0);
  fill(229,131,2);
  translate(width/2,height/2);
  rotateX(-PI*degs[0]/180);   // x axis works 
  rotateY(PI*degs[1]/180);
  rotateZ(-PI*(degs[0]+degs[1]/2)/180);
  rectMode(CENTER);
  box(100,20,100);
}

GoToLoop

Highlight your code, then hit CTRL+ K to format it! ;)

asimes

When you apply a rotation in Processing it changes the orientation of the coordinate grid. In other words, a small rotation on the x-axis "moves" the y-axis and z-axis. If you are getting measurements of angles independently of each other then just plugging them into Processing's functions won't work.

The solution that I know of is to create 8 3D points and draw the cube yourself instead of using box(). Now that you have control over the 8 points, you can apply rotations manually using matrices to actually change the location of the points instead of moving the coordinate system.

If you store the 8 3D points as aligned with the coordinate system, then every frame copy the points. You would use the copied points to draw the cube and receive accelerometer rotations.

asimes

Here is an example that shows the problem. If I rotate only the x-axis then the cube rotates on the x-axis as expected:

rotateX(theta);

If I rotate the y-axis 90 degrees (HALF_PI in radians) then the x-axis rotates to where the z-axis used to be and the z-axis rotates to where the x-axis used to be. These two lines of code visually cause the exact same behavior as only rotating the x-axis:

rotateY(HALF_PI);
rotateZ(theta);

Here is a sketch, try commenting out rotateX() then uncommenting rotateY() and rotateZ():

float theta = 0;

void setup() {
  size(400, 400, P3D);
  noFill();
}

void draw() {
  background(255);
  translate(width/2, height/2);

  rotateX(theta);

  //rotateY(HALF_PI);
  //rotateZ(theta);

  box(100);
  theta += TWO_PI/100;
}