Texturing a Sphere

Let's assume you want to create something that looks like the planet earth. You want to apply a map of the earth to a sphere.
There are 2 ways to texture a sphere. Either by applying a cubemap or by applying a 2D texture. For best result, use a cubemap. The problem with applying a 2D texture is that when you wrap a 2D texture onto a sphere, the top and bottom area of the sphere, the texture looks squeezed.

Cubemapping a Sphere

Load a cubemap as shown in Creating a Cubemap Texture
Let's assume that we'll be using shaders. If you haven't learned shaders yet, now is the time.
This code is in GLSL 1.10. The vertex shader :

  //[VERTEX SHADER]
  #version 110
  uniform mat4 ProjectionModelviewMatrix;
  varying vec3 TexCoord0;
  void main()
  {
     gl_Position = ProjectionModelviewMatrix * gl_Vertex;
     TexCoord0 = gl_Normal;
  }

The fragment shader. Notice that the normal has been copied to TexCoord0 and this will be used to sample the cubemap.

  //[FRAGMENT SHADER]
  #version 110
  uniform samplerCube Texture0;
  varying vec3 TexCoord0;
  void main()
  {
     vec4 texel = textureCube(Texture0, TexCoord0);
     gl_FragColor = texel;
  }

2D Texture Mapping a Sphere

Either you need to write your own code to create a sphere and you compute the texcoords yourself or you use another library like GLU or glhlib.

GLU

C

  GLUquadricObj *sphere=NULL;
  sphere = gluNewQuadric();
  gluQuadricDrawStyle(sphere, GLU_FILL);
  gluQuadricTexture(sphere, TRUE);
  gluQuadricNormals(sphere, GLU_SMOOTH);
  //Making a display list
  mysphereID = glGenLists(1);
  glNewList(mysphereID, GL_COMPILE);
  gluSphere(sphere, 1.0, 20, 20);
  glEndList();
  gluDeleteQuadric(sphere);
  //-----------------
  //and whenever you want to render, call glCallList(mysphereID)
  //to kill the display list, glDeleteLists(mysphereID, 1);

Java

  Texture earth;
  try {
    earth = TextureIO.newTexture(new File(dataPath("[http://www.oera.net/How2/PlanetTexs/EarthMap_2500x1250.jpg EarthMap_2500x1250.jpg]")), true);
  }
  catch (IOException e) {    
    javax.swing.JOptionPane.showMessageDialog(null, e);
  }
  GLUQuadric sphere = new GLUQuadric();
  gluQuadricDrawStyle(sphere, GLU_FILL);
  gluQuadricTexture(sphere, true);
  gluQuadricNormals(sphere, GLU_SMOOTH);
  //Making a display list
  mysphereID = glGenLists(1);
  glNewList(mysphereID, GL_COMPILE);
  earth.enable();
  earth.bind();
  gluSphere(sphere, 1000.0, 20, 20);
  earth.disable();
  glEndList();
  gluDeleteQuadric(sphere);
  //-----------------
  //and whenever you want to render, call glCallList(mysphereID)
  //to kill the display list, glDeleteLists(mysphereID, 1);

GLHLIB

If you want to use glhlib http://sourceforge.net/projects/glhlib/
The header file glhlib.h explains how to use :

  glhSphereObject2 Sphere;
  memset(&Sphere, 0, sizeof(glhSphereObject2));
  Sphere.RadiusA=1.0;
  Sphere.RadiusB=1.0;
  Sphere.RadiusC=1.0;
  Sphere.Stacks=10;
  Sphere.Slices=10;
  Sphere.IndexFormat=GLH_INDEXFORMAT_16BIT;
  Sphere.VertexFormat=GLHVERTEXFORMAT_VNT;
  Sphere.TexCoordStyle[0]=1;
  Sphere.ScaleFactorS[0]=Sphere.ScaleFactorT[0]=1.0;
  //-----------------
  glhCreateSpheref2(&Sphere);
  //-----------------
  //HOW TO RENDER (You might want to use VBO, I'm just using VA here):
  glBindTexture(GL_TEXTURE_2D, TextureID);
  //-----------------
  glVertexPointer(3, GL_FLOAT, sizeof(GLHVertex_VNT), Sphere.pVertex);
  uint mypointer=(uint)Sphere.pVertex;
  mypointer+=12;
  glNormalPointer(GL_FLOAT, sizeof(GLHVertex_VNT), (uint *)mypointer);
  mypointer+=12;
  glTexCoordPointer(2, GL_FLOAT, sizeof(GLHVertex_VNT), (uint *)mypointer);
  glDrawRangeElements(GL_TRIANGLES, Sphere.Start_DrawRangeElements, Sphere.End_DrawRangeElements, Sphere.TotalIndex, GL_UNSIGNED_SHORT, Sphere.pIndex16Bit);
  //.........and delete it when your program closes
  glhDeleteSpheref2(Sphere);