# normalize vertices

hi, i’m a noob to opengl but i have to do operations without openGL help. so far, i’ve made shapes, rotation/translation/scaling of my custom 3d shapes and now i need to do lighting and i am stuck at normalizing. i can tell that my lighting works because i added a glutSolidTeapot to my scene and it has some smooth lighting on it while my custom shapes are just all white.

i have my vertices stored like this:

verts[i][j][0] = some val for x equation
verts[i][j][1] = some val for y equation
verts[i][j][2] = some val for z equation
verts[i][j][3] = 1 for homogenous

and my shapes work. now, i don’t know how to normalize them. i think i understand that you use the cross product and then normalize but i don’t understand how to make the cross product for my vertices. i have them as “quads” not triangles if that means anything. any help on how to normalize with the way my vertices are stored would be appreciated

You need to construct normals from your vertices. You then normalise the normals not the verticies.
You can construct the normals from any triangle by using the 3 points to create a plane. By definition the normal is perpendicular to the plane. For a quad you simply have two triangles so you can pick which verticies you want when creating the plane.

i still cant get it to work. heres the code i have to calculate the normal of a shape (such as a cone, sphere, etc)

``````	while(i < 50){
while(j < 50){
calcCross(po->vertices[i][j], po->vertices[i][j+1], po->vertices[i+1][j+1], po->normals[i][j]);
j++;
}
i++;
}
``````
``````void calcCross(GLfloat *a, GLfloat *b, GLfloat *c, GLfloat *n){
n[0] = (b[1] - a[1])*(c[2] - a[2]) - (b[2] - a[2])*(c[1] - a[1]);
n[1] = (b[2] - a[2])*(c[0] - a[0]) - (b[0] - a[0])*(c[2] - a[2]);
n[2] = (b[0] - a[0])*(c[1] - a[1]) - (b[1] - a[1])*(c[0] - a[0]);
normalize(n);
}
``````
``````void normalize(GLfloat *p){
GLfloat d = 0.0;
int i;
for(i=0; i<3; i++){
d+=p[i]*p[i];
}
d=sqrt(d);
if(d > 0.0){
for(i=0; i<3; i++){
p[i]/=d;
//printf("normal: %f
", p[i]);
}
}
}

``````

with my shape on when i open the app i see

if i turn mine off and turn on glutSolidTeapot i see

anyone can tell me what i need to do to get mine to have the lighting?