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could someone check my function

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vertf* normal(vertex* st1,vertex* st2,vertex* st3) { float len; numb1.x=(float)atof(&(st1->vx[0]));numb1.y=(float)atof(&(st1->vy[0]));numb1.z=(float)atof(&(st1->vz[0])); numb2.x=(float)atof(&(st2->vx[0]));numb2.y=(float)atof(&(st2->vy[0]));numb2.z=(float)atof(&(st2->vz[0])); numb3.x=(float)atof(&(st3->vx[0]));numb3.y=(float)atof(&(st3->vy[0]));numb3.z=(float)atof(&(st3->vz[0])); v1.x=numb1.x - numb2.x; v1.y=numb1.y - numb2.y; v1.z=numb1.z - numb2.z; v2.x=numb3.x - numb2.x; v2.y=numb3.y - numb2.y; v2.z=numb3.z - numb2.z; //cross product norm.x=(v1.y*v2.z)-(v2.y*v1.z); norm.y=(v1.z*v2.x)-(v2.z*v1.x); norm.z=(v1.x*v2.y)-(v2.x*v1.y); //normalizziamo!!!!!!!!!!! len=(float)sqrt(potenzaf(norm.x,2)+potenzaf(norm.y,2)+potenzaf(norm.z,2)); if (len==0.0f)len=1.0f; norm.x/=len; norm.y/=len; norm.z/=len; return (&norm); } this function is passed 3 struct : struct vertex { char vx[15],vy[15],vz[15];} and then result a pointer to: struct vertf { float x,y,z;}numb1,numb2,numb3,v1,v2,norm; but it seem don''t works properly because when i try to display the result some polygon are invisible ,so i think the normal aren''t calculated well!

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mate this is horrendous im not surprised youve got errors , gotta make it easy on yourself by writing clean code

the cross product looks wrong

v[0] = p.v[1] * q.v[2] - p.v[2] * q.v[1];
v[1] = p.v[2] * q.v[0] - p.v[0] * q.v[2];
v[2] = p.v[0] * q.v[1] - p.v[1] * q.v[0];

try breaking the whole thing into smaller pieces. and why are your vertex stored as text?

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sorry but your cross product is exactly the same of the mine,
and the vertex are in text format because i''m calculating the normal of a model in a .off file format which is a text file format.

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youre right sorry about that it is the same. though you should have various maths classes in your project eg taken from kong

this works out a normal

VECTOR p = newWall->points[1].vertex - newWall->points[0].vertex;
VECTOR q = newWall->points[2].vertex - newWall->points[0].vertex;

u could even simplify further by going someit like

VECTOR norm = giveme_the_normal(vert1, vert2, vert3);

are u getting the right values when u convert the chars to floats
from here numb1.x=(...

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