Facet Normal Of A Triangle:
	1) Compute edge vectors using points 0, 1, 2.
		x10 = x1 - x0;
		y10 = y1 - y0;
		z10 = z1 - z0;
		x12 = x1 - x2;
		y12 = y1 - y2;
		z12 = z1 - z2;
	2) Compute the cross product of the edge vectors (to recieve the normal vector).
		cpx = (z10 * y12) - (y10 * z12);
		cpy = (x10 * z12) - (z10 * x12);
		cpz = (y10 * x12) - (x10 * y12);
	3) Normalize the result to get the unit-length facet normal.
		r = sqrt(cpx * cpx + cpy * cpy + cpz * cpz);
		nx = cpx / r;
		ny = cpy / r;
		nz = cpz / r;


The Angle Between Polygons:
	A dot product of the facet normals (unit length) returns the cosine of the angle between the vectors.


Smooth Shading:	
	Soft Edges:
		Add all (normalized) normals from the common facets then renormalize the result.
	Hard Edges:
		A different normal is generated for each side.
		* Split a vertex and compute a different normal for each of the new vertexes.


Circle Drawing:
	glBegin(GL_LINE_LOOP);
	for (i = 0; i < circle_points; i++)
	{
		angle = 2*PI*i/circle_points;
		glVertex2f(cos(angle), sin(angle));
	}
	glEnd();


Normals Flipping:
	Negate the normal coordinates