20 Replies Latest reply on Nov 25, 2013 1:01 PM by Eric Irwin

# How do I create smoother surfaces

Hello SW community,

First time on forums – I hope some1 can help.

I have a surfacing issue.  I would like to try and improve the quality of one of my surfaces.  I have tried many things but can’t get the surface to “smooth out”.

The model is attached and the surface I am interested in improving is highlighted in blue below (you may be able to see that the surface is un-smooth).  The model is attached.

Is there any1 that can help me with this surface? Or anyone that can offer some guidance as to how to go about this particular surface?

One thing I have noticed is that when the surfaces are knitted together the quality of the surface is reduced.  You will be able to see this in the model by supressing the knit feature at the bottom.

Cheers!

Hayden

• ###### Re: How do I create smoother surfaces

Try a Boundary Surface instead, tangent on left and right (of above image) and tangency influence turned up to 100%.  Looks to be nearly curvature continuous.

• ###### Re: How do I create smoother surfaces

Eric,

Thanks for your reply.  I have tried Boundary surface and the curvature continuity is not sufficient.  Looking at the model you sent there still seem to be some undulations (though slightly improved).  I have read that boundary surface should be used for 4 sided boundary - so I shall stick with this from now.

I have been playing with the model.  The boundary surface seems to work best if all the constraining lines are continuous (as one would expect I suppose).  The problem seems to be that one of the lines is not continuous.  I have replaced the non-continuous line with a continuous one and this has created a perfect surface.

Hayden

• ###### Re: How do I create smoother surfaces

Hayden,

You are thinking of continuous and non-continuous in the wrong way.  An edge/boundary can be made up of tangent entities and it will work fine.  In order to get the surface to be "curvature continuous" with the surface next to it, the curves should be curvature continuous with the surface next to it.

To evaluate the surface quality you should be using the Curvature analysis tool and the Zebra analysis tool, not just looking at reflections withing your model.  The analysis tools are much more reliable than the graphics from the standard screen.

Boundary surface is my preffered tool, mostly because you have more control.  Essentially it can do everything that a Loft can do, but has more control.  There are times when it is recommended to use Loft instead, but I can't think of those right now.

• ###### Re: How do I create smoother surfaces

Eric,

Thanks again for your reply.  I did wonder about the accuracy of the graphics display.  I wouldn't be completely reliant on this anyway but it is good to know the limitations.

Regarding what I was saying with the lines I should rephrase that because I think I have confused things.

The problem we have with this feature is that the two opposite lines I have illustrated in my previous post are not similar.  One is a spline which is a gradually changing entity, and the other is a line and an ark which makes its change after a point.  This will have to be accomodated by the feature.

Changing both lines to similar splines makes a good improvement.  The improvement is shown below:

Hayden

• ###### Re: How do I create smoother surfaces

Hayden,

I think you have it now, and yes splines will always give you better surfaces than combinations of lines and arcs.

Eric

• ###### Re: How do I create smoother surfaces

Eric,

Thanks for your help.  Much appreciated!

Hayden

• ###### Re: How do I create smoother surfaces

when I need a boundary between edges or sketches with differing numbers of entities like this, I find it helpful to add a "connector" at the entity endpoints (or sometimes the middles, and somtimes both). have you adjusted/add connectors to improve the surface yet?

• ###### Re: How do I create smoother surfaces

Jeremy,

Thanks for your reply.  Do you mean something like this?

I have tried a number of combinations - all of which seem to make things worse.  It is very difficalt to create acurve that would guide the surface because of the complexity of the boundaries.  So far I am finding that the feature does a better job then I do.

Hayden

• ###### Re: How do I create smoother surfaces

no - do not add a curve. when inside of the boundary command you should see an orb on each of the direction 1 profiles, and these orbs are connected by a line. this is a connector. you can right click anywhere on the profiles and select "add connector" and then drag the orbs along the profile(s) to control the surface.

• ###### Re: How do I create smoother surfaces

Jeremy,

Cant believe I didnt know about this.  This feature did not help me in the example above but its completely fixed another issue I had.

Cheers!

Hayden

• ###### Re: How do I create smoother surfaces

You are creating a surface using fillet edges as part of the definition.  That is a staple ingredient in surfacing disasters.

If you can, imagine what the surfaces would be without those fillets in they way and definie wour surface accordingly.

• ###### Re: How do I create smoother surfaces

Roland,

Thanks for your reply.  Im not sure I understand what you mean.  There are no fillet commands in the model though there are some surfaces that are created for that purpose.

Would you suggest creating the model as a square - then adding the fillets at the end?

Hayden

• ###### Re: How do I create smoother surfaces

Hayden,

Yes, I think you understand what Roland is trying to say.  If it were me, and I was as concerned about the quality of the side surface as you seem to be, I would create the side surfaces and the bottom surface and then the transition that is joining them.  That does depend a little on how important the joining transition lines are.

The short answer is that with surfacing, it is usually better to start with larger and more consistent surfaces that are overbuilt (if needed) and then trim them back using smaller transitional surfaces.  That will help improve your surface quality.  There are times that this cannot be done, but it is a good general practice.  It appears you are trying to build exactly what you need right out of the gate and then knit them all together and be done.  Instead I try to tell people to approach it like you were modeling in clay.  You would get the big surfaces in and smooth, then you would come back and add the details.  In the end, it is very much like solid modeling, where your fillets are added at the end.  Not quite as cut and dry as that, but similar in philosophy.

I hope that makes some sense.

• ###### Re: How do I create smoother surfaces

Thanks for stepping in, Eric.  I didn't have time for a detailed reply, but I wanted to get that part of the discussion started..  I'm glad you ran with it.

• ###### Re: How do I create smoother surfaces

I hope I didn't step on your toes, but we are all here to help and learn.

• ###### Re: How do I create smoother surfaces

Roland, Eric,

All good advice so thanks to both of you!  I had a go at creating the big surfaces first as a test and I can already see the advantages.  I think I have enough to really move forward and make some sweet surfaces!

Thanks again

Hayden

• ###### Re: How do I create smoother surfaces

As Roland mentioned fillet is a surfacing disaster and I'm also not a fillet's big fan - Is there a trick way to create a round corner in surfacing?

• ###### Re: How do I create smoother surfaces

I think that what Roland was trying to say was that you should not try to build fillets with surfacing tools, such as a boundary surface.  If you need a surface that is a fillet, then you should use the filleting tools.  That may mean that you delay adding those fillets until later, which is usually best practice in either solids or surfaces.  Trying to build a clean surface that is something like a fillet is a very bad idea, unless you simply cannot avoid it.

• ###### Re: How do I create smoother surfaces

Eric,

I got your point. What I mean here is how to create a smooth corner between 2 surfaces without using fillet surface tool? Soon I added a fillet (supposed to be tangetn to both surfaces and should have C1) and run the zebra stripes, the curvature seems to be broken like C0 at that corner

Thx

• ###### Re: How do I create smoother surfaces

A boundary surface or loft will usually get the job done, but may require some guide curves to get what you are looking for.  Both of these tools will use some interpolation, so if you have a long skinny surface in the end, the curvature is going to change from start to finish.  Adding the guide curves can help to minimize this issue.