Joining two polysurface

i have a hull having two polysufaces but those arent joining to each other , may be there is some modelling error in it. i am sharing my problem here, please someone look into it014- HALF SHIP final 2.3dm (2.6 MB) thnx
i use it on laptop

Hi, there are several problems in the model: the intersection between two polysurfaces is not a single curve but is made of 25 different curves; there are also other surface issues like folds and disontinuities that will make it very difficult to build a single polysurface and would result in bad geometry anyway.

Another issue is that the “lofting profiles” are actually made of a curve and a line connected without any tangency continuity so the resulting loft is made of two surfaces - a curved one and a planar one with a sharp edge - you should add at least add fillet between the line and the curve.

Another major problem is that the large transition surfaces has only four edges, while it should be a polysurfaces with 6 naked edges: if you check it, you’ll see that there is a single long edge with two sharp curvatures instead of three distinct edges. This generates an extreme fold and makes it impossible to create blends.

Overall, I think it would be easier to rebuild the entire front section, starting by recreating the base curves rather than try to fix all the issues.


i have tried it 2-3 times, may be i dont have that much knowledge of this, can u look into this, i am sharing a editable file.
thanks.013- HALF SHIP.igs final.3dm (1.7 MB)

I’m afraid that you are not going to get all that far with the given input. I don’t know what the purpose of the file will be in the end of course, but I reckon you should work on the input curves and start over.
This picture shows just one issue:

On of the frames is too short and leads to a bump in the hull.
Also, the bottom of the hull should be 100% horizontal, not sloping downwards like in this case.

For a good tutorial on how to build hulls in Rhino, look here:

There is a PDF and a 3D model that you can download and study.

can you please show me how to give loft command by applying it on this model , it is a as it is ship given by manufacturer .010-Lines Plan HALF ship WITH BULB POSITIONED.3dm (896.4 KB)

I would start by adding ship hull model to this forum topic to attract help from experienced ship modelers.

These curves are really bad. Various point counts. Some are polycurves with multiple segments. There are curve alignment issues. It makes it really difficult to determine how to create these surfaces accurately.

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can you help me out here? i am unable to loft it, i am sharing a editable file.010-Lines Plan HALF ship WITH BULB POSITIONED.3dm (896.4 KB)

the info supplied in video and pdf is not sufficient to make this ship . can you give it a loft command, i am sharing a editable file010-Lines Plan HALF ship WITH BULB POSITIONED.3dm (896.4 KB) that would be very helpful.

I played with this a little, just out of curiosity. Because of the unappealing surface generated with a loft, I decided to Rebuild all of the hull curves. I did it in two parts. First, everything except the stern, where the lines separate into an upper and lower part. In order to keep the basic shape as consistent as possible, I rebuilt the curves very, very heavy with 999 control points. If you just do that and loft the rebuilt curves, the hull surface is quite nice. Stupid heavy with so many control points, but the surface quality is nice.

Next, to keep the control point density roughly the same, I selected the stern lines and rebuilt them with 500 control points.
In order to ultimately be able to loft/create a surface to connect with the hull, I took those rebuilt curves and did a Blend Curve with Tangency to each of the upper and lower pairs of curves. Joined the 3 curves (upper, lower and blend), and then lofted those curves. At this point there is a gap between the hull and stern. I did a BlendSrf between the two lofts and joined all 3 surface segments, hull, stern and blended connecting surface.

The blend curve on the originally separated upper and lower stern curves cause the loft to “drift” to the other half of the ship. I went to Front View, drew a line vertically and split off the “overhang”. After that, you should be able to Mirror that hull half and Join to get something that will float. Ha!
I know that this is a very inelegant workflow, to build a model this heavy, but this method pretty much aligns the control points so the lofted surface is quite smooth, scrupulously maintains the original hull curve shapes and is fairly fast, compared with fussing with each hull curve. I know there must be better ways to do this, but this first stab was just on a whim, and ends up looking better than it did when I started.

You could play around with rebuilding the curves with fewer points and monitoring how much shape deviation you’re willing to accept. Face it, almost any number of control points will give a markedly smoother surface than if you loft the curves, as-is. Too few, and the rather sharp corner at the bottom, just off the keel, will be more rounded than you’d likely want. It is only for that reason that I chose to rebuild so heavy. You know better what you’ll be willing to accept for your model.

Best regards,

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