Trying to fill a complex hole in model while retaining G2 continuity

I’m basically trying to fill the hole in the example provided. The front of the model is supposed to be as smooth as possible (like a high speed train). But that front has to flow into the topology at the back, but I can not get it to work. I’ve tried blend, sweep, network, edge, patch etc. but I am unable to create a watertight surface. Does anyone know how to do this?

Example.3dm (244.4 KB)

Should the front match the curves?

The existing fillets/blends are not G2 continuous with the existing flat surfaces, which makes it impossible to have G2 continuity everywhere between the existing surfaces and new surfaces. A transition will be needed.

Do you have any idea on how I should do this? I have literally tried everything I know how to do.
Also, I would already be very happy if the model was watertight.

First step is to clean up and simplify the surfaces you are trying to match. DupBorder the existing border. Untrim the existing surfaces, Delete duplicates. Then trim the remaining surfaces with the original border. ShrinkTrimmedSrf to It can be simplified to three surfaces and two fillets/blends.

The front needs to be designed. It is not a simple “fill in a hole” exercise.

How familiar are you with Rhino? Are you a student?

I am still learning Rhino (yes I am a student) And designing the front is exactly where my knowledge of Rhino stops. I’m currently in the process of cleaning up my existing model.

Ok, so let’s start over. I’m trying to create a smoothe transition from the blocky back to the smooth Hhigh speed train like front.

Example.3dm (188.2 KB)

Is this the sort of shape you are trying to create?

Examplex.3dm (525.5 KB)

My .02 worth - similar structure to Jim’s but I tried to clean up the curves a bit.
Example_PG.3dm (394.4 KB)

Hmm - I guess I left that transition surface a little lumpy - but that is the idea anyway.


Could you explain to me what basic steps you took to create this? I’m especially interested in the part between the top curve blend and the bottom crv2view curve you used. How did you create such a controlled and smooth surface inbetween these two curves?

Hey Pascal, a few quick questions:

Am I right in assuming that you combined CrvBlend and Crv2View to create most guide curves? After which you used a combination of EdgeSrf and BlendSrf to create the surfaces?

Hi Luc - I made two curves - the profile curve and the plan curve - these are just a little cleaner versions of what you had.
These were then extruded - the very top surface was then point edited to give it the taper shape. The top/front surface was changed in degree to 3 (ChangeDegree, Extrusions are 1) to give it more points and a ‘flexible’ structure, MatchSrf-ed to the top surface for curvature - this gives a similar tapered swoopy shape. I trimmed the front of this with a smooth blend curve. The vertical surface was made the same way - extruded a short distance, changed to degree 5, in this case, in the straight direction and MatchSrf-ed to your vertical side surface, Then a cleaned up BlendSrf (s) in between.