static void GetSphereArrays(GLfloat **vertex_array_p, GLfloat **normal_array_p)
{
static GLfloat vertex_array[SPHERE_NUM_VERTICES*3];
static GLfloat normal_array[SPHERE_NUM_VERTICES*3];
static GLboolean arrays_initialized = 0;
if (!arrays_initialized)
{
GLfloat cos_table[SPHERE_RESOLUTION+1];
GLfloat sin_table[SPHERE_RESOLUTION+1];
int theta_index, phi_index;
// Fill out tables.
for (theta_index = 0; theta_index <= SPHERE_RESOLUTION; theta_index++)
{
cos_table[theta_index]=cosf((2*M_PI/SPHERE_RESOLUTION)*theta_index);
sin_table[theta_index]=sinf((2*M_PI/SPHERE_RESOLUTION)*theta_index);
}
// Compute the vertices and normals.
GLfloat *vertex_p = vertex_array;
GLfloat *normal_p = normal_array;
for (phi_index = 0; phi_index < SPHERE_RESOLUTION/2; phi_index++)
{
for (theta_index = 0; theta_index<SPHERE_RESOLUTION; theta_index++)
{
#define SET_VERT(t_index, p_index) \
normal_p[0] = cos_table[t_index]*sin_table[p_index]; \
normal_p[1] = sin_table[t_index]*sin_table[p_index]; \
normal_p[2] = cos_table[p_index]; \
vertex_p[0] = normal_p[0]*SPHERE_RADIUS; \
vertex_p[1] = normal_p[1]*SPHERE_RADIUS; \
vertex_p[2] = normal_p[2]*SPHERE_RADIUS; \
normal_p += 3; vertex_p += 3;
SET_VERT(theta_index, phi_index);
SET_VERT(theta_index, phi_index+1);
SET_VERT(theta_index+1, phi_index+1);
SET_VERT(theta_index+1, phi_index);
}
}
arrays_initialized = 1;
}
*vertex_array_p = vertex_array;
*normal_array_p = normal_array;
}
void render_quarter(int n)
{
int i, j;
GLfloat step = 1.0/((GLfloat)n-1);
GLfloat x[2];
GLfloat y[2];
GLfloat normal[2][2][3];
for(i = 0 ; i < n-1 ; i++)
{
for(j = 0 ; j < n-1 ; j++)
{
x[0] = step*((GLfloat)i);
x[1] = step*((GLfloat)(i+1));
y[0] = step*((GLfloat)j);
y[1] = step*((GLfloat)(j+1));
interpolate_normal(x[0],y[0],normal[0][0]);
interpolate_normal(x[0],y[1],normal[0][1]);
interpolate_normal(x[1],y[0],normal[1][0]);
interpolate_normal(x[1],y[1],normal[1][1]);
#define SET_VERT(ix,iy) \
glNormal3fv(normal[ix][iy]); \
glVertex3f(x[ix],y[iy],0);
#define SCALE .2
if(flag & FLAG_NORMAL)
{
glDisable(GL_LIGHTING);
glColor3f(1,1,1);
glBegin(GL_LINES);
glVertex3f(x[0],y[0],0); glVertex3f(x[0]+SCALE*normal[0][0][0], y[0]+SCALE*normal[0][0][1], SCALE*normal[0][0][2]);
glVertex3f(x[0],y[1],0); glVertex3f(x[0]+SCALE*normal[0][1][0], y[1]+SCALE*normal[0][1][1], SCALE*normal[0][1][2]);
glVertex3f(x[1],y[0],0); glVertex3f(x[1]+SCALE*normal[1][0][0], y[0]+SCALE*normal[1][0][1], SCALE*normal[1][0][2]);
glVertex3f(x[1],y[1],0); glVertex3f(x[1]+SCALE*normal[1][1][0], y[1]+SCALE*normal[1][1][1], SCALE*normal[1][1][2]);
glEnd();
glEnable(GL_LIGHTING);
}
glBegin(GL_QUADS);
SET_VERT(0,0);
SET_VERT(1,0);
SET_VERT(1,1);
SET_VERT(0,1);
glEnd();
}
}
}