I've been playing around with the examples from the particle system page but I'm now trying to output one of the forms to a dxf file. it works but when I try to open the file i get an error message does any one know what i'm doing wrong? Thanks for your help.

import traer.physics.*;
import processing.dxf.*;
boolean record;

ParticleSystem physics;
Particle[][] particles;
int gridSize = 10;

void setup()
{
 size(400, 400,P3D);
 fill(0);
 framerate(60);
       
 physics = new ParticleSystem(0, 0,5,0.5);
 
 particles = new Particle[gridSize][gridSize];
 
 float gridStepX = (float) ((width / 2) / gridSize);
 float gridStepY = (float) ((height / 2) / gridSize);
 
 for (int i = 0; i < gridSize; i++)
 {
   for (int j = 0; j < gridSize; j++)
   {
     //Spring makeSpring( Particle a, Particle b, float strength, float damping, float restLength )
     particles[i][j] = physics.makeParticle(0.2, j * gridStepX + (width / 4), i * gridStepY + 20, sin(gridStepY + 20));
     if (j > 0)
     {
       physics.makeSpring(particles[i][j - 1], particles[i][j], 8.0, 0.5, gridStepX);
     }
   }
 }
 
 for (int j = 0; j < gridSize; j++)
 {
   for (int i = 1; i < gridSize; i++)
   {
     physics.makeSpring(particles[i - 1][j], particles[i][j], 8.0, 0.5, tan(gridStepY));
   }
 }
 
 particles[0][0].makeFixed();
 particles[0][gridSize - 1].makeFixed();
 particles[9][gridSize - 1].makeFixed();
 particles[9][gridSize - 10].makeFixed();

}
void keyPressed() {
  // use a key press so that it doesn't make a million files
  if (key == 'r') record = true;
}
void draw()
{
    if (record) {
    beginRaw("processing.dxf.RawDXF", "output.dxf");
  }
 physics.advanceTime(0.1);
 
 if (mousePressed && keyCode == UP)
 {
   particles[0][gridSize - 1].moveTo(mouseX, mouseY, 0);
   particles[0][gridSize - 1].velocity().clear();
 }
 
   if (mousePressed && keyCode == LEFT)
 {
   particles[9][gridSize - 1].moveTo(mouseX, mouseY, 0);
   particles[9][gridSize - 1].velocity().clear();
 }
 
     if (mousePressed && keyCode == RIGHT)
 {
   particles[9][gridSize - 10].moveTo(mouseX, mouseY, 0);
   particles[9][gridSize - 10].velocity().clear();
 }
 
   if (mousePressed && keyCode == DOWN)
 {
   particles[0][0].moveTo(mouseX, mouseY, 0);
   particles[0][0].velocity().clear();
 }
 
 background(255);
 
 for (int i = 0; i < gridSize; i++)
 {
   beginShape( LINE_STRIP );
   curveVertex(particles[i][0].position().x(), particles[i][0].position().y());
   for (int j = 0; j < gridSize; j++)
   {
     curveVertex(particles[i][j].position().x(), particles[i][j].position().y());
   }
   curveVertex(particles[i][gridSize - 1].position().x(), particles[i][gridSize - 1].position().y());
   endShape();
 }
 for (int j = 0; j < gridSize; j++)
 {
   beginShape( LINE_STRIP );
   curveVertex(particles[0][j].position().x(), particles[0][j].position().y());
   for (int i = 0; i < gridSize; i++)
   {
     curveVertex(particles[i][j].position().x(), particles[i][j].position().y());
   }
   curveVertex(particles[gridSize - 1][j].position().x(), particles[gridSize - 1][j].position().y());
   endShape();
 }
}

void mouseReleased()
{
 particles[0][gridSize - 1].setVelocity( (mouseX - pmouseX), (mouseY - pmouseY), 0 );
 
    if (record) {
    endRaw();
    record = false;
  }
}

what error message do you get?

as for things not changing based on perspective.. that's because dxf is a 3D file format. perspective has to do with how you map 3D to 2D, which is controlled by whatever application is rendering the 3D.