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View Full Version : HELP! Rhino surfaces


sepehr
06-02-2002, 08:28 PM
I'm quite new to Rhino.
My problem is surfaces I make using NetworkSrf command don't match the curves which are made of.
Specially if the surface is intended to be a thin one.
I have rebuilt the curves and surfaces with different point counts and degrees but still they don't match.
I have also changed "Tolerance" options when making the surface.
The only thing that happens is I have a surface with more or less faces.
as can be seen in the pictures below.
Even when I extude a surface from an edge of a surface the extruded surface.

What should I do?
Please help me.
Thanks in advance
:bounce: :bounce:

sepehr
06-02-2002, 08:29 PM
Another view

sepehr
06-03-2002, 10:42 AM
This might seem to be very easy to you but has stoped my modeling project in Rhino and now I have to continu it in 3DMax...

When I see the wireframe one I don't find anything wrong and they seem to be match properly.....!!!

So is this a Rhino bug?
:thumbsdow

Wiro
06-03-2002, 01:03 PM
been a while since I used Rhino heavily but have you tried combining the surfaces?
Surfaces are sometimes tesselated differently (depending on when or how they were created and if they have been modified later) and even though the curves match the polygons may not. You may also get it right again by updating the tesselation, but I can't remember where that was (I don't have Rhino here right now)...possibly in the options.
Combining surfaces tells rhino that they definartely belong together and so the tesselation should be the same on all.

Wiro

Grey
06-04-2002, 12:40 AM
Select the surfaces and type JOINSRF

If the suerfaces refulse to join, type JOINEDGE and select the edges

If that doesn't work, type PTON for both surfaces, turn OSNAP on to Point and snap the points on one surface edge to another. Then they'll join.

NETWORKSRF works bestt if the curves line up.

Use OSNAP NEAR and INTERPCRV when creating your cross cureves this way they'll all be touching. If they're not, Rhino has to interpolate between the actual position of the curves, and it's often not pretty.

sepehr
06-04-2002, 10:25 AM
Thanks for your comments
But still as you can see the wireframes of the same extruded curves with different degree,point count,... fit the curves but
their shaded view has problem and doesn't match the curves and
the wireframe.

So I think I should first make the whole car in one surface and then trim parts.

I did so and the trimed surfaces edges fit together but still their
edges are very sharp ,So ry to estrude their edges but again the
extuded surfaces don't match the trimed surface edge.

perhaps I have to make a surface between two trimed surfaces edges and then try to use something like blend surfaces or fillet
surfaces (which I don't know their differences,but I usually use blend) to make a soft edge for them.

sepehr
06-04-2002, 10:26 AM
Another question is does increasing surface point counts have any effect on the shape of shaded surface and its
face counts?

Grey
06-04-2002, 11:14 PM
the hurdle will be to replace your trimmed surfaces with untrimed ones. I generally never have a trimmed surface unless there's a boolean union or difference involved (or if I CAP an object).

Rebuildsrf may change the shape of your surfaces slightly. What I tend toward is either double the pointcount on the U or V direction (depending on which I need to increase) or get as close to double as possible.

This will decrease the amount of variance in the surface shape.

If you do this with all your surfaces, you'll be able to snap in the seams.

this is a good example of where it may be wise to use NETWORKSRF use EXTRACTWIREFRAME and set up a network off that from your trimmed surfaces.

tobalno3
06-04-2002, 11:15 PM
i tried rhino once..........

Grey
06-04-2002, 11:58 PM
one other thing regarding surfaces with naked edges, when you go to export them, it's sometimes a pain to figure out how rhino is facing the normals.

One of the big reasons I close all my surfaces is because rhino always faces normals OUT (unless I specifically tell it to face them in...

I rarely use surfaces with naked edges... As to making your car a single surface, that may be a solution for you.

I know FORD uses rhino for designing car bodies, but I never heard what their primary method of doingso is within rhino. Single Surfaces with trims may be it.

What you may consider is doing your body as a single surface, closing it at the bottom and using Boolean operations to add detail to it like cutting out the windshield, hood seams, wheel wells, etc...

This will give you a high quality object in rhino which will be easier to get a high integrity mesh from (assuming you're meshing it).

sepehr
06-05-2002, 11:31 AM
Thanks Grey
I rebuilt the surface,when I clicked the preview button,
every thing seemed to be right and the surfaces seemed
to match properly.
Then I clicked on ok button and the shaded surfaces returned to
their previous situation again but wireframe ones had much more
control points.
So I tried to export these all to 3dmax and there all surfaces
seemed to match each other properly.
So this is a Rhino bug when it wants to show shaded surfaces.

About trimming solution:
I'm modeling in this way from a tutorial I found at:
http://www.suurland.com/gallery_stills_newbeetle.htm

Mr Thomas suurland has made a very nice Beetle car using
trim solution and the surfaces seem to fit each other tightly.


Here is the picture:

Grey
06-06-2002, 12:28 AM
no, it's not a bug!!!!

Rhino tesselates the NURBS for shaded preview, in effect, creating polygons for each object.

It's called Tesselation, and every NURBS program with preview does it. (some engines render nurbs without tesselation, but this is a different animal, slow as molasses and unsuitable for preview).

IF the surfaces are NOT joined, it will create separate polygon surfaces which will invariably have gaps.

I'm trying to remember how to adjust this, and I know there was a way... I can't seem to find it. I never need to because I always join my surfaces when I don't want to see gaps.

Grey
06-06-2002, 12:30 AM
sorry, forgot to add this part.

IF you need to know that your seams match up, do a Joinsrf then shownakededges with the object selected. If it shows the edges you just joined highlighted, you know they don't match.

Wadus
06-06-2002, 02:45 AM
Hi, it looks like you need to go into the render properties and change the mesh setting to smooth and slower...

Grey
06-06-2002, 03:18 AM
DOH!

I was looking right at that tab too!

Nice Save, thanks :D

sepehr
06-06-2002, 08:15 PM
Thanks all.
I think this thread has helped me alot.
That's why I like here.
I think the problem is solved now!
:beer:
I'll post the result when I finish it.
(I'm a university student and next week I have 6 exmas!,
I think I'd better go and study my lessons)

Teyon
06-07-2002, 03:17 AM
And I think I know exactly what your problem is and I have a feeling, it's so simple to fix you may kick yourself. Go to RENDER>PROPERTIES and click the tab that says RENDER MESH. I'm willin gto bet it's set to Jagged & faster. This is why your preview meshes look awfull. Just click the Smooth & slower option or set up your own and that should make everything all purty.

I hope that helped and if not, send me the piece that's causing you trouble (not the whole model, just that part) and I'll see if I can figure it out for ya.

sepehr
06-08-2002, 05:46 PM
Thanks Teyon
Yeah that solved the problem.
(Grey & Wadus had told me this too, thanks Grey,thanks Wadus)

I think my problem was I used to 3dmax interface and its viewports.
(in 3dmax Nurbs are kinda heavy objects which always match the curves unless
the user sets them to lower quality settings(surface approximation)).
:thumbsup:

sepehr
06-08-2002, 05:47 PM
Ok
just another question:
Which one is a better way(?):
Extuding a trimed edged in Rhino with command "Extrude" then moving the new surface
and using "FilletSrf" to make a smooth surface between the two edges then using "Join"
command to join these three.

or

Exporting the surface to another software like 3dmax ,then selecting the edges of the trimed surface
and extuding them,then assigning a new smooth ID to these new surfaces?

------------------------------------------
Something else I have just rememberd:
Does joined surfaces have bad effects (on their joined edges) when assigning a reflective
material to them?
I mean will be there such a problem if I make surfaces of one half of the car
and then mirror and join them?

Grey
06-08-2002, 06:24 PM
I wouldn't use filletsrf unless you really must.

I'd much rather find my edges, trim it off and use blendsrf which gives me a lot more control over the curve. It'll be more tedious, so if it's a time issue, then filletsrf will probably work better for you.

Though when doing fillets I usually use FLTE between joined surfaces instead. (but I still like blendsrf better).

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