Hello,

At this state of my learning curve, I have some questions refering to the 3 numbers of the respecting arrows shown within the attached image :


1) why do this surface disappears from its edge ?

2) How can I make a surface covering this half empty circle ?

3) how can I erase this edge to obtain a smooth unique surface here ?

Thank you very much for any help,
Best Regards,

Hi Guy, is it possible for you to post the 3DM model file of your object there instead of just a screenshot?

It usually helps quite a lot to be able to deal with the actual geometry that your question involves, because I'm able to do a lot of things to geometry such as rotate it to different angles, zoom in to it, and also just use your actual file to demonstrate things with, none of these things are possible for me to do on just a screenshot instead of the actual model.

#1 looks like it's just likely to be a display artifact - in order to display the shaded surface area, MoI has to convert surfaces into a triangle mesh and in some situations where your surface has fairly shallow or gentle curvature it can get not quite enough triangles created for the display in those areas, leaving a kind of polygonal silhouette to the shaded drawing.

That kind of thing is purely a display artifact, it does not mean that your actual surfaces are that way, and if you for example export to a polygon mesh format using a high density for the export you should see that area getting refined during the export.

Curves are drawn to a higher precision than the shaded surface areas - curves get broken down into lines dynamically so that the lines used for the display are within 1 pixel of the true curve. It's unfortunately too calculation intensive to do the same dynamic refinement for surfaces so surfaces only get one static triangulation which is used at all zoom levels, so that's why there can be some mismatch between the shaded surface display and the edge display.

Some previous discussion here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4926.25
http://moi3d.com/forum/index.php?webtag=MOI&msg=4860.1

In general it's a focus for the display mechanism to do things fast and also to do things within the constraints of how the video card is set up to operate, so it's not unusual for there to be various kinds of display artifacts since trying to do a perfect looking display like an "offline render" does is much slower.


> 2) How can I make a surface covering this half empty circle ?

Are you sure it's empty? It kind of looks like it already has a surface there, if you can post the model file I can more easily check it.

If it is empty and it's a planar opening you can seal that off by selecting the object and using Construct > Planar.


> 3) how can I erase this edge to obtain a smooth unique surface here ?

Those are 2 smaller surfaces coming together at that common edge - in order to not have an edge there you would instead need to create a larger extended surface that went across that full area and that larger surface could then be trimmed to have the inner notch hole area cut out of it.

Often times if you want smooth pieces it's best for the smooth piece to be made up of one larger surface (done with one large sweep or network or whatever), and then that large single surface can get cut where necessary to remove portions of it.

Also depending on your shape there it might have been better to have made that whole surface done more as a boolean operation slicing away material from a larger block, I'm not entirely sure since I am not able to examine your model yet but it looks like you may be modeling things in a sort of more "patch by patch" method rather than building larger extended blocks and then slicing the big block up.

Generally if you can build extended pieces which then get cut it's a better workflow than trying to build things one little patch fragment at a time.

- Michael

Hi Michael,

Thanks for point #1, that's all what I needed to know :-)

About #2 I cannot do that with planar, I have tried and re-tried, but nothing seems to work.

& for the #3 yes, I made it small by small steps. This curve is the result of a line tangent to an ellipse joined then extruded. As it was joined as line tangented I thought the surfaces was smooth enough to not make an edge...
Well, I will try to make big solids then cut in with bolean to obtain the good shape.


Anyway it could be so cool if you could show me !
There you will find the 3dm file in attachment, please use it at your convenience.

My Best,

> how can I erase this edge to obtain a smooth unique surface here ?

it's not if there is a line(s), that want say that the surface are not smooth for a renderer engine!

If you disable in the Browser Visibility of Edges, you can see that these surfaces are some smooth ;)

If you want absolutly no line you must repair your object!
Verify that you have not Points who are not necessary!

The more easy is Copy Past from the original some parts and reconstruct them ;)

If you have 2 same curves kill one and copy move the last for be sure that they are not fliped!

Then at the end kill false original parts and assemble with news :)



Ps Don't put your object with any orientation in the floating space
because we must rotate it and past it on the gride
for more easy to work on it ;)
(times won)

Hi Guy - thanks for posting the file, that makes it a lot easier to answer your questions about it!

For #2 - there is not any hole there, you already have a surface in that spot, here I have selected it to help show it to you more clearly:



So you don't need to do anything at all to fill in that hole - there is no hole there, it's filled in by a planar surface there already.

The only part that actually needs to be filled in is the very top of the piece where you do actually have a hole here:



To fill in that place that really does have a hole, select the whole object by one click on it so that the whole thing is selected like this:



Then run the Construct > Planar command here:



That will fill in an end cap in that planar opening of the object, sealing it off and making it into a solid now:




re: #3 - you actually don't need to worry about that either - it looks like you did a good job constructing your original curves making them tangent to one another and with extrusions if the generator curves are tangent the surfaces that are created are tangent too regardless of whether they are in multiple pieces or not.

So your object is already nice and smooth at that spot, it's ok that there is an edge there, in this case that is just part of the topology of your object and does not automatically mean that it is not smooth, although that could be the case in other situations like if your generator curves were not smooth to begin with or if you had a more complex type of surface there that was flexing and bending in the middle of it and not just an extrusion.

But anyway your object is actually smooth there already, here I've done an polygon mesh export with a high polygon count and shaded mode set, you can see that your existing object is smooth there:



It's normal for extrusions to inherit the segmentation of their generator curves - when a curve is made up of multiple different segments joined together, then when you extrude it the extrusion will be made up of multiple faces joined together with one face for each segment in the original joined curve. That's not an error, that's how it's supposed to work. The different pieces of the extrusion will be smooth to one another if the segments of the generator curves were smooth to one another like yours were.

If you do have just one single curve segment instead of multiple joined pieces, you will definitely have a smooth piece though because you can only have sharp corners in a curve at segment junctures. So sometimes it is convenient to eliminate segmentation in a curve to smooth out any small corners in it. That can be done by turning on control points and deleting the control point where 2 segments meet which will fuse them together into a single segment or also the Rebuild command can be helpful for some kinds of curve repair cases: http://moi3d.com/2.0/docs/moi_command_reference10.htm#rebuild However in your case here you've done a nice job making the curve segments constructed so that they are tangent to one another so there is no problem in having things as segments in this case.

Hope this helps!

- Michael

Hi Michael,

Say : for sure this helps a lot ! :-D

Thank you very much for your time taken to work on my file and to answer me.
This helps me a lot also with my understanding of MoI. (How to use Rebuild function with shortcuts or tab&typing, re-make point curves etc.)

Strange : yesterday I was sure to have checked the lack of this small surface on the top of the half-cylinder without seeing any kind of surface...
Anyway maybe I was too tired, so today is a very good day with its good news :-)

Again thank you very much for your excellent help.

Best Regards,

< That will fill in an end cap in that planar opening of the object, sealing it off and making it into a solid now

!!!
Never seen seen that!!! I was selecting each edges of a future face! :)
here a simple click on one face of the object make the trick :)

So in fact Planar is an automatic close volume engine !

Hi Pilou,

> !!!
> Never seen seen that!!!

But yes you have! :) Because didn't you translate the reference for Planar here which describes it and shows an example too? :
http://moi3d.com/2.0/docs/moi_command_reference7_French.htm#planarsrf

:)

But yes, it's a shortcut - if you select an entire surface object instead of selecting curves you can then run Planar and it will find sets of open edges that make planes, then construct the planes there and join them in to seal them off, so it combines a few steps doing it that way.

- Michael

Yes i did indeed :)

but don't realised that for one simple rectangular face in a box no need to select the "4 sides" of the hole against just click an adjacent face one!

Now that is fixed in my mind ! :)

Hi Pilou - you don't need to select any individual faces at all actually, you just select the whole object with just one click so the whole thing is selected and then run Construct > Planar. Any planar openings will get sealed up.

- Michael

Yes only one click on one face if the object is boolean unioned like the model of this thread ;)

And the "4 sides" if by hasard you want in your model just one hole face planed ;)

So many possible combinaisons