Patch and loft to point tangent problems

[Anonymous]

Hello,

I am working on constructing tumours as accurate as possible.

I have a few hundred points that describe the circumference of the bottom and one point for the top of the tumour.

Overview:

So far I use the bottom points to create a spline which I turn into a patch surface. Afterwards I loft between the patch and the top point. Since this is a biological shape a loft to point to tangent would be far preferable to lofting to a sharp point. I have a solution using a rail in the loft command but am looking for improvements.

First issue:

The patch surface doesn't look quite right. Some points are not included (picture: missing_point_waves). And the patch looks like it has waves in it. The points used to create the splines lie on a sphere, as should any point on the patch/bottom of the tumour.  I would be thankful for any ideas on how to fix this, or for completly different approaches since I'm new to modelling via UI.

If I just ignore the patch problem and continue with lofting I get the

Second issue:

Loft to sharp point works, but loft to tangent doesn't. 

Warning: Loft to point would have non-smooth neighbourhood of point.

I tried making it easier for fusion by including an intermediate patch between bottom and top point which has smoother edges by removing quite some points used for the bottom. 

But trying to connect the botton and the intermediate level through lofting causes a loop edges error.

Right now I am using loft to sharp point together with rails. For the rail I pick two opposing bottom points and the top point. (This doesn’t always work, maybe because the patch doesn’t always include every point, but I wasn’t able to reproduce this error right now, so it’s not so important.)

The resulting body is ok (picture: rail_result), but if anybody has an idea on how to resolve the patch problem, the point tangent loft without using rails, or knows of a completely different solution I would be glad to hear it. A smoother surface would be preferable but I understand if it’s not possible.

Greetings,
Saskia

P.S. The splines and patches were created via API.  All the important structures are in the example, the intermediate patch is included but it also contains all the points the bottom patch has.  The size of the intermediate level is adjustable if it helps in any way.

[TrippyLighting]

Can you explain what you want to do with the result ?

the reason I am asking this is that any attempt to model this with splines and lofts in any CAD software is like not going to be very successful. Lofting creates NURBs surfaces and those surfaces work best with a limited number of spline points and curves.

such irregular surfaces are better modeled with Sub-D modelers and perhaps even sculpting software, but whether that is an option really depends on what you intend to do with the model.

[Anonymous]

Hello,

Yeah I can answer that:

The tumour will be used to cut away and replace parts of a simple eye model I have in Fusion. Afterwards I use the Fusion API to cut all the bodies in my model, including the tumour, with small cubes. The resulting tumour and eye "cubes" need to be exported as .stl files so that I can use them in another program for a simulation.

The uneven upper surface is not that important since I have no real information what the tumour looks like anyway and  it is furthest away from my radioactive source in the simulation. But somehow I need to get the bottom in a spherical shape. I tried cutting a sphere with the right diameter (22mm) with the tumour, so that I could add the spherical button to the tumour but again I just get an error:

Error: There was a problem combining geometry together.
If attempting a Join/Cut/Intersect, try to ensure that the bodies have a clear overlap (problems can occur where faces and edges are nearly coincident).
Failed to Boolean bodies together

Maybe because the tumour bottom circumference points lie on the sphere?

Anyway if it is somehow possible to get the spherical bottom in Fusion I would be really happy, since the entire workflow is already implemented in the Fusion API and maybe  I would be able to implement the tumour construction there as well. 

Greetings,
Saskia

[Anonymous]

short update:

By using boundary fill I was able to create the bottom part of the tumour between the patch and a sphere with the correct radius. But once again I get an error when I try to combine the bottom part of the tumour with the lofted top part.

[TrippyLighting]

Can you share your latest file ?

[Anonymous]

Here is the latest version of my design. 

It would be great, if I could combine the tumour_bottom with the tumour_top and if I could use the resulting body to cut for example the sphere.