Maxsurf to Freeship

[GavinM]

Hi Everyone,

Thanks for all the help so far and sorry for all the threads. I'm wrapping this design up soon though!

Anyways, I have been trying to compare a few canoe hull designs for a student competition and keep running into problems. I designed the hulls in Maxsurf Academic and have faired the designs, calculated hydrostatics etc for all of them. I would really like to do some resistance and stability calculations but it sounds like that is beyond the scope of maxsurf Academic. Now I'm trying to use freeship but am running into problems getting my model accurately (even close to accurately) from Maxsurf to Freeship. I searched around and only found threads from 2006 and 2008 but none that led me to a solution.

I have a surface in Maxsurf that I would like to import into freeship so that I can gather the info on stability, resitance, etc. I have tried importing as a surface, but with no luck. I can't seem to get the table of offsets right in maxsurf although I think that's something I'm getting closer to.

I have tried exporting from maxsurf as a 3d nurbs surface igs file and importing from there as well as many other options.

Can anyone point me in the right direction to help me get from maxsurf to Freeship?

Reallly appreciate all the tips so far, been very helpful.

GavinM

[GavinM]

Anyone? I still haven't had any luck getting it on my own, tried exporting from freeship as .igs, nurb surface, polylines, etc all to no avail... I've been getting closer but once I get something in it is missing the bow and stern stems... Trying to import from a table of offsets or coordinates does not produce anything though. As in literally nothing will show within freeship. I can't help but think I'm still just doing something wrong even though I've tried importing exactly as it says to in the manual...

Thanks

[yipster]

You | I can work around it but looking given horses deep in the mouth you may try the freeship forum or try victor T's version, dont know, just ideas

[bhnautika]

GavinM freeship has a limited number of options for importing but I have got surfaces into freeship from maxsurf using a third programme as a filter. You can import using “VRML” (version 1) through, say Rhino (iges) or a polycad file (may need surface conversion in polycad from the original iges). Once in freeship it will be almost impossible to edit the surface as the number of control points will be huge!

[GavinM]

Thanks, I still can't get it to export correctly for some reason though. I got help with the basic analysis so the in depth analysis can wait a few days, but now I am still having problems exporting it to solidworks. On bringing in the .igs file, solidworks warns of intersection geometry errors and won't let me offset the surface or use it to create a model of the mold.

[APP]

Originally Posted by bhnautika

GavinM freeship has a limited number of options for importing but I have got surfaces into freeship from maxsurf using a third programme as a filter. You can import using “VRML” (version 1) through, say Rhino (iges) or a polycad file (may need surface conversion in polycad from the original iges). Once in freeship it will be almost impossible to edit the surface as the number of control points will be huge!

Infact, also VRML from Multisurf to Freeship works, but too many control points, the computer is not moving. Any work-around in Multisurf before exporting the VRML? or any method to reduce the control points produced?
Thanks
APP

[bhnautika]

App Unfortunately VRML surfaces are meshes based on small individual faces rather than a group of control points globally controlling the underlying mesh. You can usually reduce the number of mesh faces that are used in the exported file by reducing the precision of the original file (as in maxsurf or the slider in the export mesh in say, rhino, multisurf may have something similar). The problem is this reduces the smoothness and accuracy of the surface, so it depends on what you want to do with it once its been imported as how far you want to go in reducing.

[APP]

Originally Posted by bhnautika

App Unfortunately VRML surfaces are meshes based on small individual faces rather than a group of control points globally controlling the underlying mesh. You can usually reduce the number of mesh faces that are used in the exported file by reducing the precision of the original file (as in maxsurf or the slider in the export mesh in say, rhino, multisurf may have something similar). The problem is this reduces the smoothness and accuracy of the surface, so it depends on what you want to do with it once its been imported as how far you want to go in reducing.

Thanks. I shall try to find something similar in Multisurf or Fastship but I doubt it, has someone tried these two?
Regards
APP

[CmbtntDzgnr]

Gavin,

Try this:

-- Export the hull from MaxSurf as a dxf file

-- Import it into PolyCAD

-- In PolyCAD, inspect the file to make sure your control points are not excessive in count

-- Convert the surface or mesh parts into BSpline surfaces

-- Save the file as a PolyCAD file (it will have the file type extension .geo)

-- Open Free!Ship/Hydronship 3.26 + Test

-- Import the PolyCAD

If you do not see any message such as "No BSpline Surfaces Found", you should be okay.

To do calcs, you'll need to at least add stations, probably waterlines, buttocks, and diagonals, too -- depending on what you need.

Also, go into Project/Project Settings and click on the tab named "Main Dimensions" and enter the L/B/T information.

Run the various appropriate (or inappropriate if you wish) files Victor generously provides.

If it turns out you cannot run reports because you have a bazillion "leak points" or just too many to want to deal with, then return to PolyCAD and consider the various other surface types into which you can change the surface or mesh so that you can reduce the points count.

You may need to do so, and to do so, select each station and press F2 to put the curve into Edit mode. If you see some 20 or more control points, consider exiting Edit mode and using this right-click command:

"Fit Uniform BSpline Using Least Squares"

ying to each station/curve that probably is a polyline. Don't delete the originals -- you've already faired them, so keep them as references after you rename them.

If you have a visual clutter of stations work the hull in 1/4s from fore to aft, and then re-inspect from amidships to fore, and amidships to aft, and then satisfy yourself that the stations don't undesirably cause any unfaired surfaces somewhere along the way.

-- Edit the new BSplines with the F2 key, and drag the control points as necessary.

-- Create new BSpline surfaces for those newly-made BSpline curves

-- Select the surfaces and turn on the Isophote and other surface/visualations options settings to inspect your work before saving the file.

When satisfied, or at some intermediat stage to not spend too much time, do some test saves of the file with the surfaces as BSpline surfaces.

You may want to select ONLY the BSpline surfaces, copy them, and paste into a new file, and save THAT file containing ONLY the BSpline surfaces, and then importing that file into Free!ship.

Having imported the file into Free!ship successfully, you may swim in the reports there.

While in PolyCAD, though, don't overlook that "Quick Hydrostatics" button on the upper right of the menu bar. Whether your hull is one piece or multiples, that will show you the various hydros for that whole hull if it is a single piece, or each "compartment" if you built up the model station by station. To get it to work, select all the stations or the whole model, then in the Entities Selector (hit F10 and F11), select everything, then go into Quick Hydrostatics, and then enter the first few letters of an existing entity that is part of your area of interest. Once familiar, you can double-click to turn off layers not of interest. If you have graphics card issues or depending on your version of window, then don't double-click there-- just select via mouse and hit "Ctrl+h" to hide items that clutter the view or overload the QH display list.

As for other hydros at various drafts, select the stations, right click, create PolyCAD hull, and then click on the menu for Hydrostatics (not the Quick Hydrostatics button!), and enter various drafts. Check out the Free-Floating Hydrostatics item, too. You can set heel angles and generate GZ curves, and if you left-click and drag your mouse along the graphic/chart, you'll see your hull incline and them BMG targets move around. Pretty neat!

I hope these steps work for you and prove interesting, too. I've spent the past week diving into PolyCAD and giving feedback and liking VERY much what I see and what I am learning. Don't forget to check out the Macro Editor, where you can generate compartments and tanks. Playing with that as addictive and I only got 2.5 hours of sleep last.. umm, this morning before coming to work.

Note: If your hull is built up by station, and if you use the "Fit Hull" command, each section in the boundaries sections of the macros must be named to match the area that will cut the tank. Otherwise, don't use Fit, and you can lop off the excess in an external CAD app. But, doing it in PolycAD is a time-saver.

Cheers!

[bhnautika]

APP what facility is it in freeship that you need to import from multisurf or fastship

[APP]

[quote=CmbtntDzgnr;504574]Gavin,

Your reply to Gavin:

"Try this:

-- Export the hull from MaxSurf as a dxf file

-- Import it into PolyCAD

-- In PolyCAD, inspect the file to make sure your control points are not excessive in count

-- Convert the surface or mesh parts into BSpline surfaces
....................................."

How exactly are you doing this hull conversion into BSplines? {Sorry, I am not familiar with PolyCAD}
Thanks
APP

[APP]

Originally Posted by bhnautika

APP what facility is it in freeship that you need to import from multisurf or fastship

Nothing special, just curious to know.

[fcfc]

Maxsurf, solidworks, rhino, IGES file format, and other do handle internally mathematical object NURBS surfaces.

Freeship uses internally mathematical object subdivision surface. When you import an IGES surface, it does recompute the subdivision surface closest to your IGES surface. That why you get a catastrophically great number of control points.

[CmbtntDzgnr]

Hi APP,

Just select the surfaces by pointing and clicking on it and then right-clicking on it go get the context-sensitive dialog to open. On that form/list of applicable options, you will see several conversion options.

To make it easier to select items, look at the lower edge of the program and sight the "Highlight" box. There, you can right-click and activate one or more options that will help you know more of what is beneath the mouse's current position. This is really helpful when you have stations that are duplicate, or are very near each other when in Stations view. In the case of stations, for example, putting the mouse pointer close to the geometry would make are rectangular label appear, showing the name of the geometry. I suggest you rename each station to something such as "STN 15". If you subdivide your shell plating or boat fuselage for whatever reason, or have skins or panels in the model, abbreviate those accordingly, and, optionally color code them. I color code stations so that -- particularly in Stations view -- they are easier to follow. Since I am not good with the color wheel, I just go by "ROYGBIV", and color the stations stem to stern, making sure no two stations adjacent or semi-overlapping have too similar a color. Makes for easier designing and troubleshooting. Similar can apply to Waterplane view of decks or tanks that are trimmed against the hull (say, buy use of the Macro Editor). For Buttocks view, in the case of non-mirrored yet symmetrical items, Highlighting helps there, too.

So, in short, select an item, then right-click. You will get DIFFERENT contextual options DEPENDING ON the line or surface types. If you create a PolyCAD hull with polylines, it sometimes can become too easy to expect to do it with other lines, but what is possible or not will be learned by right-clicking on anything you can think of in the drawing.

[APP]

Thanks. I will give it a try.

Originally Posted by CmbtntDzgnr

Hi APP,

Just select the surfaces by pointing and clicking on it and then right-clicking on it go get the context-sensitive dialog to open. On that form/list of applicable options, you will see several conversion options.

To make it easier ..........................