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Index › Programming Questions & Help › Syntax Questions › coordinate of an object in a 2dim array
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coordinate of an object in a 2dim array (Read 656 times)
Mohammed
coordinate of an object in a 2dim array
Jul 21st, 2009, 3:00am  
Hello,

how can i find the coordinate of each of my box ? Maybe i have to create an array for my object but i don t understand how i can link
this with my 2dim array of position.
Then my controls doesn t work, i think it s because my calculation is in my setup part and consequently the calculation of my variable is closed but what can i do ? Here the code :

int samples = 20;
PVector [][]pos = new PVector[samples][samples];
float a1 = 10., a2 = 10., a3 = 10.;
float u1 = 0., u2 = 20., v1 = 0., v2 = 20.;
float dU = (u2 - u1) / samples;
float dV = (v2 - v1) / samples;
float n = 1., e = 1.;

void setup(){
 background(0);
// size(screen.width,screen.height, P3D);
 size(500,500, P3D);
directionalLight(126, 126, 126, 0, 0, -1);
camera(-15,15,-20,0,0,0,0,0,1); //get a viewpoint

float u = u1;
  for(int i=0; i<samples; i++){
   float v = v1;
   for(int j=0; j<samples; j++){
     float x = a1 * sqCos (u, n) * sqCos (v, e);
     float y = a2 * sqCos (u, n) * sqSin (v, e);
     float z = a3 * sqSin (u, n);
     pos[i][j] = new PVector(x, y, z);
   
   v += dV;
     }
   u += dU;
}
}

void draw(){
background(0);
   rotateY(frameCount * 0.01);
   for(int i=0; i<samples; i++){
    for(int j=0; j<samples; j++){
      pos[i][j].display();
}}}

float sign ( float x ) {
 if ( x < 0 )return -1;
 if ( x > 0 )return 1;
 return 0;
}
float sqSin( float v, float n ) {
 return sign(sin(v)) * pow(abs(sin(v)),n);
}
float sqCos( float v, float n ) {
 return sign(cos(v)) * pow(abs(cos(v)),n);
}

void keyPressed() {
 if (key == CODED) {
   if (keyCode == UP) {
     n = 3.;
     e = 3.;
   }
if (keyCode == LEFT) {
     n = 1.;
     e = 1.;
   }
if (keyCode == RIGHT) {
     n = -0.2;
     e = 1.;
   }
if (keyCode == DOWN) {
     n = 1;
     e = 0.3;
   }
}
}
class PVector{
float x, y, z;
 PVector(float xInput, float yInput, float zInput){
  x = xInput;
  y = yInput;
  z = zInput;
 }

void display(){
     pushMatrix();
     translate(x, y, z);
     box(1);
     popMatrix();
}
}
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PhiLho 
Re: coordinate of an object in a 2dim array
Reply #1 - Jul 21st, 2009, 3:29am  
Note that PVector class already exists in Processing. That's not a real problem but in general I try and avoid to mask native classes.

And you guessed it, you should put the calculation part in a separate function, to call each time you update the parameters.
Either you keep it as is, letting Java garbage collecting the old PVectors (might result in a performance hit), or you separate object creation and update, and just change the x, y, z values in the existing PVectors.
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Mohammed
Re: coordinate of an object in a 2dim array
Reply #2 - Jul 21st, 2009, 5:44am  
Great ! i put my calculation in a function, it works perfectly, i can control my object. Thank you PhiLho.
But i don t manage to find the coordinates x, y, z of each cube. I tried with a println("x") but the result is strange. Maybe i have to create an  array for my cubes in order to identify each of them. How can i find these coordinates ?
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PhiLho 
Re: coordinate of an object in a 2dim array
Reply #3 - Jul 21st, 2009, 8:52am  
Mohammed wrote on Jul 21st, 2009, 5:44am:
But i don t manage to find the coordinates x, y, z of each cube.
I don't understand your problem. The coordinates are in your PVector, no
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Mohammed
Re: coordinate of an object in a 2dim array
Reply #4 - Jul 21st, 2009, 9:27am  
I don t understand how i can find the coordinates of my cube. What is
the synthax ? i wrote println(pos[1][10].x); but it doesn t work.
Println function doesn t return anything, i ve got a NullPointerException.
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PhiLho 
Re: coordinate of an object in a 2dim array
Reply #5 - Jul 21st, 2009, 10:44am  
I don't know where you put your println, but it works for me.
For example, taking your first code above, I put the line:
println(pos[1][10].x + " " + pos[1][10].y + " " + pos[1][10].z);

just at the end of setup() and it works.
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Mohammed
Re: coordinate of an object in a 2dim array
Reply #6 - Jul 22nd, 2009, 8:50am  
you are right !! thank you for your help PhiLo !!
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