/*
 
 Textured sphere example
 
 for basic construction method, see http://local.wasp.uwa.edu.au/~pbourke/texture_colour/spheremap/
 
 Textured sphere implementation
 
*/
 
float PI = 3.14159f;
float texturedSphereX[][];
float texturedSphereY[][];
float texturedSphereZ[][];
float texturedSphereU[][];
float texturedSphereV[][];
int texturedSphereDetail;
 
/**
 * Set the detail level for textured spheres
 */
void texturedSphereDetail(int detail) {
  if (detail == texturedSphereDetail) return;
   
  texturedSphereDetail = detail;
   
  // construct the underlying vertex and uv map data
   
  float step = PI / detail;
  float ustep = 0.5f / detail;
  float vstep = 1.0f / detail;
 
  texturedSphereX = new float[detail + 1][2 * detail + 1];
  texturedSphereY = new float[detail + 1][2 * detail + 1];
  texturedSphereZ = new float[detail + 1][2 * detail + 1];
  texturedSphereU = new float[detail + 1][2 * detail + 1];
  texturedSphereV = new float[detail + 1][2 * detail + 1];
   
  for (int i = 0; i <= detail; i++) {
    float theta = step * i;
    float y = cos(theta);
    float sin_theta = sin(theta);
    float v = 1.0f - vstep * i;
     
    for (int j = 0; j <= 2 * detail; j++) {
       float phi = step * j;
       float x = sin_theta * cos(phi);
       float z = sin_theta * sin(phi);
       
       float u = 1.0f - ustep * j;
      // println(u + ", " + v);
       
       texturedSphereX[i][j] = x;
       texturedSphereY[i][j] = y;
       texturedSphereZ[i][j] = z;
       texturedSphereU[i][j] = u;
       texturedSphereV[i][j] = v;
 
    }  
     
  }
}
 
/**
 * Create a textured sphere with the supplied radius and material
 */
void texturedSphere(float radius, PImage material) {
  // build the sphere by stacking up cross sections
  // KLUDGE: the poles could be built more efficiently
  int nexti;
  for (int i = 0; i < texturedSphereDetail; i = nexti) {
    nexti = i + 1;
    beginShape(TRIANGLE_STRIP);
    texture(material);
    for (int j = 0; j <= 2 * texturedSphereDetail; j++) {
       float u = material.width * texturedSphereU[i][j];
       
       float x1 = r * texturedSphereX[i][j];
       float y1 = r * texturedSphereY[i][j];
       float z1 = r * texturedSphereZ[i][j];
       float v1 = material.height * texturedSphereV[i][j];
       
       float x2 = r * texturedSphereX[nexti][j];
       float y2 = r * texturedSphereY[nexti][j];
       float z2 = r * texturedSphereZ[nexti][j];
       float v2 = material.height * texturedSphereV[nexti][j];
       
       vertex(x1, y1, z1, u, v1);
       vertex(x2, y2, z2, u, v2);
    }  
    endShape();
  }   
} 

/**
 * Drag it with the mouse
 */
float mouseDeltaX;
float mouseDeltaY; 

void mouseDragged(){
  mouseDeltaY = (pmouseY-mouseY);
  mouseDeltaX = (pmouseX-mouseX);
  if (abs(mouseDeltaX) > abs(mouseDeltaY)) {
    spin -= 0.01f * mouseDeltaX;
  } else {
    tilt += 0.01f * mouseDeltaY;  
  }
}