API for UBER H3 to (OpenGL) verteces, triangles, normals.

[SkybuckFlying]

It would be helpfull if there was a UBER H3 api which would return arrays containing enough information to visualize the UBER H3 world via for example OpenGL.

One of these APIs could look like:

H3Error getTriangularWorld( int Resolution, VectorStruct *VectorArray, Triangle *TriangleArray, Vector *NormalArray );

The purposes of this API would be to connect (lines) triangles between all hexagon centers. The initial idea was to connect lines, but lines don't visualize well in OpenGL, no backface culling for lines. So a better idea is to visualize the lines by drawing triangles instead, computing normals for triangles is possible and by setting them when the 3 vectors are added to OpenGL for the triangle, OpenGL will know how to backface cull these triangles, which is handy to not show the back of the earth/world.

Where VectorArray is a dynamic array of
VectorStruct
{
float x,y,z;
};

Where TriangleArray is a dynamic array of
TriangleStruct
{
int64 vi1, vi2, vi3; // vector index.
}

Where NormalArray is a dynamic array of
VectorStruct

VectorArray should be filled with all coordinates of the centers of all hexagons at the specified resolution.

TriangleArray should be filled with all indices of the triangles which describe the hexagon. The order of the indices should be such that when computing the plane normal (using formula below) it's pointing outwards.

NormalVector := CalcPlaneNormal
(
VectorArray[ TriangleArray[ Index ].vi1 ], VectorArray[ TriangleArray[ Index ].vi2 ], VectorArray[ TriangleArray[ Index ].vi3 ]
);

TAffineVector = VectorStruct;

function CalcPlaneNormal(const p1, p2, p3: TAffineVector): TAffineVector;
var
V1, V2: TAffineVector;
begin
VectorSubtract(p2, p1, V1);
VectorSubtract(p3, p1, V2);
VectorCrossProduct(V1, V2, result);
NormalizeVector(result);
end;

procedure VectorSubtract(const V1, V2: TAffineVector;
var result: TAffineVector);
begin
result.X := V1.X - V2.X;
result.Y := V1.Y - V2.Y;
result.Z := V1.Z - V2.Z;
end;

procedure VectorCrossProduct(const V1, V2: TAffineVector;
var vr: TAffineVector); overload;
begin
vr.V[X] := V1.V[Y] * V2.V[Z] - V1.V[Z] * V2.V[Y];
vr.V[Y] := V1.V[Z] * V2.V[X] - V1.V[X] * V2.V[Z];
vr.V[Z] := V1.V[X] * V2.V[Y] - V1.V[Y] * V2.V[X];
end;

procedure NormalizeVector(var V: TAffineVector);
var
invLen: Single;
vn: Single;
begin
vn := VectorNorm(V);
if vn > 0 then
begin
invLen := RSqrt(vn);
V.X := V.X * invLen;
V.Y := V.Y * invLen;
V.Z := V.Z * invLen;
end;
end;

function VectorNorm(const V: TAffineVector): Single;
begin
result := V.X * V.X + V.Y * V.Y + V.Z * V.Z;
end;

function RSqrt(V: Single): Single;
begin
result := 1 / Sqrt(V);
end;

[SkybuckFlying]

For now I am mostly interested in winding order of the triangles, any triangle, be it from hexagon itself or from connecting centers.

Normals do not seem to play a roll in winding order and back face culling. However maybe normals could also be used to darken verteces or lines that face away from camera/eye, etc.