Replace sphere with ellipses in 3D mode

Haagse

Dear all interested readers,

The next sketch makes this:

A 3D grid with spheres, to be rotated with the use of peasy.

I would, however, replace the spheres by ellipses, to make a better PDF output. But, of course, when I replace a sphere with an ellipse, the ellipse would rotate and loses the shape of a perfect circle.

What would it take to maintain the orientation of the ellipse while rotating the cube?

Thanks in advance for helping me out :-)

code:

---

import processing.pdf.*;
import peasy.*;
import peasy.org.apache.commons.math.*;
import peasy.org.apache.commons.math.geometry.*;

PeasyCam cam; 

int afstand = 70;

boolean record;

void setup() {
  size(600, 600, P3D);
  cam = new PeasyCam(this, 10000);
  noStroke();
  fill(0);
  ortho(-width, width, -height, height);
}

void draw() {
  background(#ffffff);

  if (record) {
    beginRaw(PDF, "cube.pdf");
  }

  for (int i=0; i<8; i++) {
    for (int j=0; j<8; j++) {
      for (int k=0; k<8; k++) {
        pushMatrix();
        translate((i-3)*afstand, (j-3)*afstand, (k-3)*afstand);
        sphere(10);
        popMatrix();
      }
    }
  }

  if (record) {
    endRaw();
    record = false;
  }
}

void keyPressed() {
  record = true;
}

Chrisir

look at reference of PeasyCam; is there a way to receive the current angles (i guess there are 2)?

jeremydouglass

@joshuakoomen --

Hmm. Just brainstorming -- I wonder if you could use screenX to retrieve 3D coordinates and then draw ellipses on a separate buffer image at the corresponding screen location.

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

kfrajer

Instructions:

*** Remember that in peasyCam you can double click in your sketch to reset the current cam view of your sketch. While keeping this in mid, then:

1- Use key r to toggle the option to show rotated ellipses or no rotation at all 2- Use key s to save into pdf 3- Assuming you start from init cam state, press either x,y or z to rotate 90 deg on that axis. You can use dbl-click to see the action of recovering your init cam orientation aka. what axis the restoration is happening on 4- Use p to print the current rotation matrix on the console as reported by peasycam

Kf

import processing.pdf.*;
import peasy.*;
import peasy.org.apache.commons.math.*;
import peasy.org.apache.commons.math.geometry.*;

PeasyCam cam; 

int afstand = 70;

boolean record;
boolean rotateEllipses=false;

void setup() {
  size(600, 600, P3D);
  cam = new PeasyCam(this, 10000);
  noStroke();
  fill(0);
  ortho(-width, width, -height, height);
}

void draw() {
  background(#ffffff);

  if (record) {
    beginRaw(PDF, "cube.pdf");
  }


  strokeWeight(5);
  stroke(0, 255, 0);
  line(-width, 0, width, 0);

  noStroke();
  for (int i=0; i<8; i++) {
    for (int j=0; j<8; j++) {
      for (int k=0; k<8; k++) {
        pushMatrix();
        translate((i-3)*afstand, (j-3)*afstand, (k-3)*afstand);

        if(rotateEllipses){
          float[] rot=cam.getRotations();
          rotateX(rot[0]);
          rotateY(rot[1]);
          rotateZ(rot[2]);
        }

        //sphere(10);
        ellipse(0, 0, 25, 10);
        popMatrix();
      }
    }
  }

  if (record) {
    endRaw();
    record = false;
  }
}

void keyPressed() {
  if (key=='s')
    record = true;

  if (key=='p') {
    println(cam.getRotations());
  }

  if(key=='r')
  rotateEllipses=!rotateEllipses;

  if (key>='x' && key<='z') {

    float[] rot=cam.getRotations();
    //switch(key) {
    //case 'x':
    //  rot[0]=HALF_PI;
    //  break;
    //case 'y':
    //  rot[1]=HALF_PI;
    //  break;
    //case 'z':
    //  rot[2]=HALF_PI;
    //  break;
    //}

    //MORE compact than above
    rot[key-'x']=HALF_PI+0.05;
    cam.setRotations(rot[0], rot[1], rot[2]);
  }
}

---

koogs

But the OP wants the ellipses to always face the front, like billboard sprites.

Whenever I've done this I use a 2d renderer and do the 3d rotation calculations myself and just use the X and y coords of the result. You're using ortho so there's no perspective to worry about. You won't be able to use peasycam though.

jeremydouglass

I wonder if you could use PeasyCam as the interface, translate to get the xyz coordinates at 0,0,0 -- and then retrieve a 2D x and y for each using e.g.

ellipse(screenX(0,0,0), screenY(0,0,0), 20, 20);

The catch is:

In order to get flat/ortho results you would then need to draw the ellipses onto a 2D PGraphics -- not into the P3D space. So the base sketch is P3D with PeasyCam interface, and the output buffer is default Java2D. However I am not sure how/if rendering a PGraphics interacts with the PDF beginRaw().

Haagse

Thank you all so much for the tips. Kfrajer's post was really helpful.

@jeremydouglass I have been thinking about that kind of solution, but I wouldn't know how to plot it correctly. Also, Kfrajer's solution was very effective for what I needed to achieve.

koogs

there's no reason the pdf writing part has to use the interactive part of the code - just put it inside a big if (record) block