You need to map a point (u,v), your latitude and longitude to a sphere point (x,y,z). Decide on a relatively close estimate for the earth's circumference, say r = 6378km at the equator. The longitude angle is given by Theta = 2*pi*u. The latitude angle is given by Phi = pi*(v-0.5). If you are starting with latitude and longitude the points (x,y,z) on the sphere can be calculated by: x = r*sin(theta)cos(phi)  y = r*sin(phi) and z = r*cos(theta)cos(phi)

Simply iterate through your longitude and latitude coordinates and plot the 3d points (x,y,z).

Good luck

Rob

Hi, Im trying to do something very similar, which is simply map a texture to a sphere. I dont see a way to do this easily with any 'built in'/'free' spherical mapping solution, so I am trying to port this code ( http://www.codeguru.com/Cpp/G-M/opengl/texturemapping/article.php/c5589/#more ) to processing. I am able to draw my sphere just fine, but I am missing a few peices, namely the author of the original code calls :

Code:

NormalVector(u,v,w,n);
    glNormal3dv(n);
 

which I am assuming makes a normal vector from the 3 coordinate vectors u,v,w, and then runs glNormal3d(n) on the vector, before drawing the textures.

What can I do in processing that mimics this?

here is my altered code, for what its worth. Any help is appreciated!

Code:

//
// code ported from http://www.codeguru.com/Cpp/G-M/opengl/texturemapping/article.php/c5589/
//

float PI = 3.14159265359;
float TWOPI = 6.28318530718;
float DE2RA = 0.01745329252;
float RA2DE = 57.2957795129;
float FLATTENING = 1.0/298.26;
float PIOVER2 = 1.570796326795;


void sphereWithTexture(PImage texture, int detail, float radius)
{
  beginShape(TRIANGLES);
  texture(texture);
  fill(200,200,200,100);
  int NumLatitudes = detail;
  int NumLongitudes = detail;
  
  float start_lat = -90;
  float start_lon = 0.0;
  float R = radius;

  float lat_incr = 180.0 / NumLatitudes;
  float lon_incr = 360.0 / NumLongitudes;

  int row, col;

  for (col = 0; col < NumLongitudes; col++)
  {
    float phi1 = (start_lon + col * lon_incr) * DE2RA;
    float phi2 = (start_lon + (col + 1) * lon_incr) * DE2RA;
    for (row = 0; row < NumLatitudes; row++)
    {
	float theta1 = (start_lat + row * lat_incr) * DE2RA;
	float theta2 = (start_lat + (row + 1) * lat_incr) * DE2RA;
    
	float[] u = new float[3];  
	u[0] = R * cos(phi1) * cos(theta1);    //x
	u[1] = R * sin(theta1);		    //y
	u[2] = R * sin(phi1) * cos(theta1);    //z
	
	float[] v = new float[3];  
	v[0] = R * cos(phi1) * cos(theta2);    //x
	v[1] = R * sin(theta2);		    //y
	v[2] = R * sin(phi1) * cos(theta2);    //z
	
	float[] w = new float[3];  
	w[0] = R * cos(phi2) * cos(theta2);    //x
	w[1] = R * sin(theta2);		    //y
	w[2] = R * sin(phi2) * cos(theta2);    //z
	
     // normal(u,v,w); // yeah, that totally doesnt work...
	vertex(u[0],u[1],u[2], (180.0 - phi1*RA2DE)/360.0, (theta1 + PIOVER2)*RA2DE/180.0);
	vertex(v[0],v[1],v[2], (180.0 - phi1*RA2DE)/360.0, (theta2 + PIOVER2)*RA2DE/180.0);
	vertex(w[0],w[1],w[2], (180.0 - phi2*RA2DE)/360.0, (theta2 + PIOVER2)*RA2DE/180.0);		
	
	v[0] = R * cos(phi2) * cos(theta1);    //x
	v[1] = R * sin(theta1);		    //y
	v[2] = R * sin(phi2) * cos(theta1);    //z
	
	//normal(u,v,w);
	vertex(u[0],u[1],u[2], (180.0 - phi1*RA2DE)/360.0, (theta1 + PIOVER2)*RA2DE/180.0);
	vertex(v[0],v[1],v[2], (180.0 - phi1*RA2DE)/360.0, (theta2 + PIOVER2)*RA2DE/180.0);
	vertex(w[0],w[1],w[2], (180.0 - phi2*RA2DE)/360.0, (theta1 + PIOVER2)*RA2DE/180.0);   
	   
    } // end NumLatitudes for loop
  } // end NumLongitudes for loop
  endShape();
}