[SOLVED] Recreate convex from saved cloud

[TSX]

Hi all! I'm writing an editor for my game physics, and I need to re-create convex hull collision from previously saved vertex cloud (custom de/serialization to own format).
So, I call NewtonCollisionGetInfo() to get vertex cloud and creation params (vertex count, face count, stride) from a convex.
But when I create new convex with these params, vertex cloud is simplificated, so I get incorrect result even if 'tolerance' parameter is zero.
Is there any way to create new convex without internal simplification? I'm using Newton 2.29.Thanks.

[Julio Jerez]

If Parameter tolerance is zero, the convex will use all point in convex surface and it will gerenate a absulte perfec hull.
When I say perfect I mean absolute exact hulls.
if it does not do that it is a bug, but I never see that before. can you post and image?

It may be possible that the conveHull shape made modifications to the exact hull to remove edges that are flat,
has you tryed the MeshCreateConvexHull.
MeshCreateConvexHull always generates exact hulls with no interrnal simplifications.
It is also faster if you are using it in and editor.
CollisionConvex Hull call Mesh CreateConvexHull and then conveted it to the collision format which is a double conected edge list.
Then it try to optimized for collision by removing as many edges that are complanar, by it does not touch vertex list.

can you show me the code you are using fo this?

[TSX]

Hi, Julio!
Тhis is a convex built from model (low-poly building).


I save convex data to TCFConvex class:

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function TNewtonCollisionFile.AddConvexIndirect(
  const pSrc: PNewtonCollision): TCFConvex;
var param: TNewtonCollisionInfoRecord;
    i: integer;
begin
  Result := nil;
  NewtonCollisionGetInfo(pSrc, @param);
  if param.m_collisionType = SERIALIZE_ID_CONVEXHULL then begin
    Result := TCFConvex.Create(Self);
    with Result do begin
      m_Vertices := param.shapedataconvexhull.m_vertexCount;
      m_Stride := param.shapedataconvexhull.m_vertexStrideInBytes;
      m_Faces := param.shapedataconvexhull.m_faceCount;
      setLength(pData, m_Vertices*(m_Stride div sizeOf(single)));
      for i := 0 to pred(m_Vertices) do
        pData[i] := TCFSingleStride(param.shapedataconvexhull.m_vertex)[i];
    end;
  end;
end;

where pData is TCFSingleStride (array of single), I'm using single-precision x86 Windows version of newton.dll.
Then I write this extracted data to a file.

When I load saved file from disk, I read m_Vertices, m_Stride, m_Faces and vertex cloud, then I create convex using

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NewtonCreateConvexHull(pWorld, m_Vertices, @pData[0], m_Stride, 0, 0, @m[0][0]);

And I get this result:


Maybe I'm doing something wrong?

P.S. I've tried to create convex through temporary mesh:

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  pMesh := NewtonMeshConvexHull(pWorld, m_Vertices, @pData[0], m_Stride, 0);
  Result := NewtonCreateConvexHullFromMesh(pWorld, pMesh, 0, 0);
  NewtonMeshDestroy(pMesh);

but still got result shown in a second picture...

[Julio Jerez]

But in the secund image the convex is completly wrong.
that is not a simplication problem that is a big Bug.
you have to have a bug in the function that get the vertices count from get Info.

can you post here a test file with the mesh, or the mesh file so tah I can check that out?

[TSX]

I've found an error, that was my mistake
I forgot to multiply vertexCount... So only first vertexCount of floats were written to dump.

Thanks for answers, Julio.

[Julio Jerez]

Oh cool, I have a question, I saw the image and it look very cool.
My question is how do you make you Toobar buttons?
I am having a hard time trying to make cool looking one for the Official newton Editor.

[TSX]

I draw some icons manually, some (move, rotate, scale) were taken from Unreal Editor.

[Julio Jerez]

Hi TSX I just want to let you know that now that newton is Open source
you can in fact make the convex hulls directly using the Geometric Class that the engine uses and bypass all the simplications that the physics engine apply to the final result
here is the class:

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class dgConvexHull3d: public dgList<dgConvexHull3DFace>
{
   public:
   dgConvexHull3d(dgMemoryAllocator* const allocator, const dgFloat32* const vertexCloud, dgInt32 strideInBytes, dgInt32 count, dgFloat32 distTol);
   virtual ~dgConvexHull3d();

   dgInt32 GetVertexCount() const;
   const dgVector* GetVertexPool() const;
   const dgVector& GetVertex(dgInt32 i) const;
}

basically it makes an absolutly perfect convex hull from the vertex cloud, it is by far more accurate and much faster than QHull,
and all of the utilities that are around, this is because Newton does not quantize the values like QHull does.
I hope this is what you wanted and I could not give you an answer before.

[TSX]

Hi, Julio!
I think this is really cool that Newton is OpenSource now
And thanks for your answer about convex