void calculatenormal(float v1[3],float v2[3],float v3[3],float &normalx, float &normaly,float &normalz){
	
	
	
	float d1[3] = { v2[0] - v1[0],   v2[1] - v1[1],   v2[2] - v1[2] };
	float d2[3] = { v3[0] - v1[0],   v3[1] - v1[1],   v3[2] - v1[2] };
	
	float cross[3];
	cross[0] = d1[1] * d2[2]   -   d1[2] * d2[1];
	cross[1] = d1[2] * d2[0]   -   d1[0] * d2[2];
	cross[2] = d1[0] * d2[1]   -   d1[1] * d2[0];
	float dist;
	dist = 1/sqrt( (cross[0]*cross[0]) + (cross[1]*cross[1]) + (cross[2]*cross[2]));
	
	normalx = -cross[0] * dist;
	normaly = -cross[1] * dist;
	normalz = -cross[2] * dist;

.......... 


glBegin(GL_TRIANGLE_STRIP);
float v1[3]={0,1,0};
float v2[3]={1,0,0};
float v3[3]={1,0,1};

float normal[3];
calculatenormal(v1,v2,v3,normal[0],normal[1],normal[2]);

glNormal3fv(normal);
glVertex3fv(v1);
glVertex3fv(v2);
glVertex3fv(v3);

glEnd();

........

glBegin(GL_LINES);float start[3]={(v1[0]+v2[0]+v3[0])/3,(v1[1]+v2[1]+v3[1])/3,(v1[2]+v2[2]+v3[2])/3};float stop[3]={start[0]+normal[0],start[1]+normal[1],start[2]+normal[2]};glVertex3fv(start);glVertex3fv(stop);	glEnd();