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Index › Programming Questions & Help › Programs › Spinning a Sphere
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Spinning a Sphere (Read 1413 times)
fankof
Spinning a Sphere
Mar 12th, 2010, 8:35am  

Hallo guys,

I`ve taken a Processing course this semester and I was very excited about the effects that a Designer can achieve with some few lines of code! We made some assignments and everything was running nicely...until I`ve started my course project.

Now to the question. I want to create a Sphere made out of dots and rotate this sphere with different speeds and directions. I have the code to create the sphere, but I cant start spinning it in any way....

I would be very very thankful if any of you guys could give me some clues to start with, because the end of the term is comming...

Code:

void drawSphere()
{
 float posy = height*.25;
 float sizey = height/2;
 int nRings = 29;
 for(int i=1; i<nRings; i++)
 {
   float phase = i*1./nRings;
   float ringCenterPosX = width / 2;
   float ringCenterPosY = posy + (sin(phase*PI+HALF_PI)*.5+.5)*sizey;
   float ringSizeX = sin(phase*PI)*sizey/2;
   float ringSizeY = ringSizeX / 4;
 
   drawRing(ringCenterPosX, ringCenterPosY, ringSizeX, ringSizeY);
     
 }

}

void drawRing(float posx, float posy, float sizex, float sizey)
{
 noStroke();
 fill(1,.5);
 int n = 100;
 for(int i=0; i<n; i++)
 {
   float phase = i*1./n;
   float r = 2;
   ellipse(posx + sizex*cos(phase*TWO_PI), posy + sizey*sin(phase*TWO_PI), r,r);
 }
}

My final goal is to achieve an ingenious effect I saw on flicker,but I`m not allowed to post a link on the forum :( neither can I upload a photo of the sphere...
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Cedric
Re: Spinning a Sphere
Reply #1 - Mar 12th, 2010, 9:09am  
post a link and change the url by adding spaces or writing "dot"
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sloopidoopi
Re: Spinning a Sphere
Reply #2 - Mar 12th, 2010, 9:20am  
I guess you mean an arcball control:
http://www.v3ga.net/processing/ArcBall/
http://www.chronotext.org/bits/030/index.htm
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Cedric
Re: Spinning a Sphere
Reply #3 - Mar 12th, 2010, 10:15am  
looking at your code i would say the problem is that it is not really 3d. its actually just a 2d sphere that looks 3d
you can use this formula to create a real 3d sphere out of points

x = cos(phi) * sin(theta);
y = cos(theta);
z = sin(phi) * sin(theta);

you can than simply use rotate
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fankof
Re: Spinning a Sphere
Reply #4 - Mar 13th, 2010, 4:11am  
Thanks, I`ll plunge into the Arc code in a second and try to implement it in a way?! ...

let me try to post the link to flickr:
flickr(dot)com/photos/alexposada/sets/72157622778283574/
flickr(dot)com/photos/alexposada/sets/72157623578136140/

So this is what I`m after. It looks astonishing and I`m quite sure it is not that hard to realize in Processing. I only have to come over this spinning problem to get this brilliant motion effect....

So back to work. Further questions to come...
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fankof
Re: Spinning a Sphere
Reply #5 - Mar 13th, 2010, 4:28am  
Hi Cedric,

yes you are totally right. my code just simulates 3d. I looked at your suggestion and try to use it, but I cant figure out how to find the (theta) angle ? for (phi) I would use my (phase)  that creates the iteration for building the rings ...

Oh God, my maths it just too poor Sad

x = cos(phi) * sin(theta);
y = cos(theta);
z = sin(phi) * sin(theta);

you can than simply use rotate [/quote]
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fankof
Re: Spinning a Sphere
Reply #6 - Mar 13th, 2010, 4:50am  
Code:
void setup()
{
  size(400,400);
  //colorMode(RGB,1);
  background(0);
 
  cX = width/2;
  cY = height/2;
 
  phi = 30.0;
  theta = 90.0;
  
  angle = 0.0;
  speed = 0.04;
  noLoop();
}


void draw()
{
  float phase = angle*speed; 
  
  x = cos(phase)*sin(theta) + cX;
  y = cos(theta) + cY;
  z = sin(phase)*sin(theta);
  
  angle+=10;
  
  size(10, 10, P3D);
  beginShape(POINTS);
  vertex(x, y, z);
  endShape();
  
}



no. cant get it working in any way.... and yep, I`m a novice.... but still trying and trying. If you would help me I`ll be very very grateful !

Tanks in advance
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Cedric
Re: Spinning a Sphere
Reply #7 - Mar 13th, 2010, 5:15am  
i quickly put together a sketch showing what i was talking about. we placed the boxes n 3d space using the sin/cos and then can simply use rotate to rotate the sphere

Code:
void setup() {
  size(600,400,P3D);
  smooth();
  background(255);

}

int radius = 100;
void draw() {
fill(200);
stroke(150);

  translate(width/2,height/2);
  rotateY(radians(mouseX));
  rotateZ(radians(mouseY));
  background(255);

  for (int i = 1; i < 36; i++){
    for (int j = 0; j < 36; j++){
pushMatrix();
	float cx = cos(i) * sin(j)*radius ;
	float cy = cos(j)*radius;
	float cz = sin(i) * sin(j)*radius; 
	translate(cx,cy,cz);
     box(3);
popMatrix();
    }
  }

}
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fankof
Re: Spinning a Sphere
Reply #8 - Mar 13th, 2010, 6:19am  
Thank you very much Cedrik!

I guess this should do the work. as soon as I have any results I will let you know Smiley

Right....

--------------------------

Is there a way to use a normal point and not a 3d box, because as soon as I increase the number of the elements performance decreases drastically?


may be something like:

Code:

pushMatrix();
	float cx = cos(i) * sin(j)*radius ;
	float cy = cos(j)*radius;
	float cz = sin(i) * sin(j)*radius; 
	translate(cx,cy,cz);

	stroke(0);
	strokeWeight(5);
	beginShape(POINTS);
	vertex(cx, cy, cz);
	endShape();


?

ThnU!

--------------------

it works. nice!!

now I have to bring in the color.
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« Last Edit: Mar 13th, 2010, 1:36pm by fankof »  
 
Cedric
Re: Spinning a Sphere
Reply #9 - Mar 13th, 2010, 7:47am  
sure, just replace :

translate(cx,cy,cz);
box(3);

with

point(cx,cy,cz);
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