GLvoid SetUpNormals(){  VECTOR v1,v2,v3,v4,v5,v6;  VECTOR n,n1,n2,n3,n4,n5,n6;  for (int z = 0; z < terrain.size; z++ ) {    for (int x = 0; x < terrain.size; x++ ) {	if ( z == 0 && x == 0 ) {		// back left corner - 1 tri 2 vertices		
v1 = terrain.CPoint[z+1][x] - terrain.CPoint[z][x];		v2 = terrain.CPoint[z][x+1] - terrain.CPoint[z][x];		n.Cross(v1,v2);	} else if ( (z > 0 && z < (terrain.size-1)) && x == 0 ) {		// left edge - 3 tri 4 vertices		
v1 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z-1][x+1] - terrain.CPoint[z][x];		v3 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		v4 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3); n3.Cross(v3,v4);		n = (n1+n2+n3)/3.0f;	} else if ( z == (terrain.size-1) && x == 0  ) {		// front left corner - 2 tri 3 vertices		
v1 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z-1][x+1] - terrain.CPoint[z][x];		v3 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3);		n = (n1+n2)/2.0f;	} else if ( z == (terrain.size-1) && (x > 0 && x < (terrain.size-1)) ) {		// front edge - 3 tri 4 vertices		
v1 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z-1][x+1] - terrain.CPoint[z][x];		v3 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		v4 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3); n3.Cross(v3,v4);		n = (n1+n2+n3)/3.0f;	} else if ( z == (terrain.size-1) && x == (terrain.size-1) ) {		// front right corner - 1 tri 2 vertices		
v1 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		n1.Cross(v1,v2);		n = n1;	} else if ( ( z > 0 && z < (terrain.size-1)) && x == (terrain.size-1)  ) {		// right edge - 3 tri 4 vertices		
v1 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		v3 = terrain.CPoint[z+1][x-1] - terrain.CPoint[z][x];		v4 = terrain.CPoint[z+1][x]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3); n3.Cross(v3,v4);		n = (n1+n2+n3)/3.0f;	} else if ( z == 0 && x == (terrain.size-1) ) {		// back right corner - 2 tri 3 vertices		
v1 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z+1][x-1] - terrain.CPoint[z][x-1];		v3 = terrain.CPoint[z+1][x-1] - terrain.CPoint[z][x];		v4 = terrain.CPoint[z+1][x]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v3,v4);		n = (n1+n2)/2.0f;	} else if ( z == 0 && ( x > 0 && x < (terrain.size-1)) ) {		// back edge - 3 tri 4 vertices		
v1 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z+1][x-1] - terrain.CPoint[z][x];		v3 = terrain.CPoint[z+1][x]   - terrain.CPoint[z][x];		v4 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3); n3.Cross(v3,v4);		n = (n1+n2+n3)/3.0f;	} else {		// internal - 6 tri 6 vertices		
v1 = terrain.CPoint[z][x+1]   - terrain.CPoint[z][x];		v2 = terrain.CPoint[z-1][x+1] - terrain.CPoint[z][x];		v3 = terrain.CPoint[z-1][x]   - terrain.CPoint[z][x];		v4 = terrain.CPoint[z][x-1]   - terrain.CPoint[z][x];		v5 = terrain.CPoint[z+1][x-1] - terrain.CPoint[z][x];		v6 = terrain.CPoint[z+1][x]   - terrain.CPoint[z][x];		n1.Cross(v1,v2); n2.Cross(v2,v3); n3.Cross(v3,v4);		n4.Cross(v4,v5); n5.Cross(v5,v6); n6.Cross(v6,v1);		n = (n1+n2+n3+n4+n5+n6)/6.0f;	}	n.Normalize();	terrain.CNormal[z][x].Set(n.x,n.y,n.z);    }  }}