T8 mouse exercise

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 From:  delic
7388.1 
Hello, I'm learning MoI, so I decided to draw a T8 mouse as exercise.

This mouse have minimalistic streamlined design, which I would be able to draw in 3D, preferably with curves and MoI.

http://www.rapoo.com/ProductShow.aspx?PType=8fQpYH%2b%2b7i8%3d&PID=cp6o1ZbjWGU%3d

I first tried to figure out the best way, booleans cut, sweep, or loft, but ended drawing the edges and network them.

Any advice about the method for such kind of shapes ?





Here I'm stuck with the adjacent edges of networked surfaces, cant get rid of them, even if there's no straight line in the curves used for building them. I tried to cut these edges and reblend them, but it's even worse. How would you do for building these two shapes smooth, with top and bottom as separate parts, so there can be an open edge ?




Anyway, I beginned building only the half, so I'll rebuild these shapes. Maybe tweking a seprated sweeped surface, and rebuild from that ?



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 From:  delic
7388.2 In reply to 7388.1 
Remade the top shape, deleted central sharp points, retrimmed the arcs, rebuilded but still the same sharp edges with network command, and I also tried to sweep these arcs, no sharpness, but it breaks the streamlines, the design. Same for the blend command.





I thought that the networks, if done properly, would work.

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 From:  Michael Gibson
7388.3 In reply to 7388.2 
Hi delic,

> I thought that the networks, if done properly, would work.

The main way to use Network to make a large smooth surface is to do it all in one single big network rather than making numerous separate individual pieces. Every time you make a separate piece the end conditions of that piece will not have any special relationship to the other adjacent patch and so will usually have a crease between them.

You'll even want to mirror your curves and do the entire width of the object all as one network rather than doing half and mirroring it.


It's kind of a fundamental thing that curve or surface interpolation done in separate segments rather than all in one go will have creases in it, there is some visual explanation of that here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.18
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.19


- Michael
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 From:  Michael Gibson
7388.4 In reply to 7388.2 
And ideally to get the best kind of surface quality it tends to be better to build a larger extended quad-like sheet with distinct corners in it and then have extended side walls that then intersect with each other to form the final surface boundary, rather than trying to directly construct surfaces to an irregular outline.

Something more like this:

Try to build the top surface as a large extended sheet, here using sweep but you can use network or loft if you prefer. The key thing is that you construct a broad wide surface that has the overall shape characteristics that you want and do not yet focus on the final border yet because that will come from trimming pieces of this large extended shape away:



Then doing sweep gives this:




Now to cut pieces of that away, your side walls should also be extended upwards a ways as well, here's an example using Loft to build a base block that pushes through the top surface:






Now you can use Trim or the booleans to cut these pieces with each other and trim off the excess area. If you can form a base solid then you can use booleans which tend to be more convenient. Here I've selected the base block and use Construct > Boolean > Difference with the sweep surface as the cutting object. This will slice the block into 2 pieces, select the piece you don't want which is this one:




And then that to leave the remaining solid which has both the side walls and the top extended surface cut to one another:




Using booleans and trimming should be a primary method of your construction when working with NURBS modeling. It will be very difficult to work on things in a "patch by patch" manner like you are currently doing where you're trying to draw in all the final edges of the model to start with and then surface everything directly only to those - especially when you're trying to make rounded outline corners in the middle of a curved shape it tends to be better for the rounded outline to come from a trim curve that trims away some broad surface. When you try to force a surface construction to an irregular boundary it is difficult to get good surface quality.

If your project is difficult to construct in this way using extended surfaces and cutting operations then it can be a sign that the project is possibly better done in a sub-d modeling program rather than in a NURBS modeling program, usually NURBS modeling will incorporate extended pieces with trimming and booleans when it is the easiest tool for the job.

- Michael
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 From:  delic
7388.5 In reply to 7388.4 
Thx a lot for the answer Michael.

So it seems very hard to model this kind of shapes with nurbs if you not have a parametric way to tweak the curves after the boolean trim, to get this streamlined side edge as you want.

I tried the method you showed with sweep, but couldn't get the side edge sorted as it is in the model by boolean trimming, even after many undos and redos, curves --> sweep --> bool trim -->undo twice, and again.

I can have that shape in minutes with subd, or classical poly method, but it would be a total fake for dimensions, surfaces bending etc ...
By using polys and lattices associated witrh curves it's possible to work with such kind of streamlines, similary as with nurbs.

I'm a bit disapointed, but thats learning, and also, the shape in the last 3dm/screenshot is quite near the real one or at least to what I wanted, just these weird edges are frustrating me a bit more.

Same for getting rid of these sharp edges after mirroring a half model. I didn't expected that.

And I still wonder how they've done this model, I mean the designers. I cant believe it's made with subd, you cant get any prototype out a printer from subd, no piece or hole would match another really, among other distorted curves and surfaces( and bevels and uneven thickness ...) problems I guess, and the fact they would certainly have to redraw it entirely in the end for the same reasons.

Anyway it would have be pretentious to think it's that easy to draw, ignoring the tons of work and knowledge behind such a model, I'm not a designer.
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 From:  Barry-H
7388.6 
Hi delic
I think this may help
Barry


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 From:  delic
7388.7 In reply to 7388.6 
Alright Barry-H, I'm a happy Man, it's PERFECT, exactly what I was asking for. Many many thanks Barry-H.

I tried to do a "multiple network" many times, hoping the inner edges would be smoothed as the inner arcs are, but didn't get that I have to specify the order. Forgot to ask about it in my previous posts.

I thought this was possible if curves are correctly setup with tangency along them, I carefully did it as it should be here.

Now I can do the bottom part, and draw any shapes with nice stream curves and surfaces. Cool, it was worth to try, spend time on it, and ask here. I really learned a lot already.

Look at these control points, isn't that a nice flow surface ?

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 From:  delic
7388.8 In reply to 7388.6 
Ok, I get it now, we just have to tell to the network command which edges are the U's and the V's, and select them in rows.

And it works fine with closed edges also, wow.

That's a very very nice tool ! I think it's a bit shortly described in the MoI command reference, maybe a generic guide for U's and V's regarding construct commands could help.

Connected the bottom part with two closed edges, and it seems perfect !


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 From:  delic
7388.9 In reply to 7388.8 
I made a quick gif, I think the bottom part is a good example of network :


EDITED: 10 May 2015 by DELIC

Image Attachments:
Size: 2.5 MB, Downloaded: 7 times, Dimensions: 800x499px
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 From:  delic
7388.10 In reply to 7388.9 
Messed something with the attachement, remade a lighter gif.





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 From:  Michael Gibson
7388.11 In reply to 7388.8 
Hi delic, I'm glad you are getting good results now!

re: network U and V selection - you do need to have curves that make up logical U and V directions but you don't actually need to select them in that order, the Network command automatically analyzes the layout of all the curves and sorts them into U and V sets for you. So you should be able to do a group select and get the same result. Selecting by individual clicks in order will not actually have any effect, this is an area that is a bit different between Rhino and MoI.

- Michael
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 From:  Barry-H
7388.12 
Hi Michael
Re:U V selection for network can be done by group selection.
I tried that but found that manually selecting them speeded up the calculation
on my net book.
Could the lack of processor power cause that?
Barry
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 From:  delic
7388.13 In reply to 7388.11 
Ok, so the rule is : join edges or curves to get a logical UV layout, then run network command, no need to select them in a particular order, nor to separate the U's from the V's.

I think I will use this a lot, combined with flow command it looks very smart to create objects designs from sketches.
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 From:  delic
7388.14 
I made some renders. It doesn't look as the model I tried to redraw, but the global shape is similar.

The top isn't exactly as I wanted finally, an arc is missing to bend the surface until the nose of the mouse.
Also the bevel between bottom and top part is wrong, I used a projected offset curve to blend a bevel.

I exported without merging adjacent edges, so it's easier to select and the normals are consistent. Normals are messy when merging edges at export in .obj. But the resoltution is not enough, we can see the polys of open edges in the renders here, altough I exported with resolution of .obj exporter.

Is there a way to export with way more polygons ?









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 From:  Michael Gibson
7388.15 In reply to 7388.12 
Hi Barry,

> I tried that but found that manually selecting them speeded up the calculation
> on my net book.
> Could the lack of processor power cause that?

I don't really know what would cause that, maybe you had some other process running at the same time that was also taking some of your processor time up...

As far as I know doing manual selection versus group selection should not make any difference as far as how Network processes things. For some other commands like Loft the selection order does have an effect though.

- Michael
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 From:  Michael Gibson
7388.16 In reply to 7388.14 
Hi delic,

> Is there a way to export with way more polygons ?

You should generally join surfaces together before exporting to a mesh format, joined edges will have extra work done during processing them to ensure there is a consistent vertex structure along the edge and that avoids cracks between pieces.

For generating more polygons, the first thing to try is to move the slider at the top towards the "more polygons" side, that will tighten up the angle meshing parameter and produce more polygons on curved areas of the model. If you want still denser yet you can expand the meshing options dialog by clicking on the little arrow in the lower left corner, and then use the "Divide larger than" option to force additional divisions, see here for an example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5

- Michael
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 From:  delic
7388.17 In reply to 7388.16 
Thanks Michael.

I was thinking about the "extra work", does the exporter merge only the joined edges, and leave open the others even if merge is set at export ?

Something is also unclear for me, should we consider joined surfaces the same as when they are displayed as one surface, or as a solid ?

Sometimes the edges can be joined to a solid or a unique surface, sometimes not, what is the rule have in mind there ?
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 From:  Michael Gibson
7388.18 In reply to 7388.17 
Hi delic, I'm sorry but I'm not understanding much of what you write here...

> I was thinking about the "extra work", does the exporter merge only the joined edges,
> and leave open the others even if merge is set at export ?

Well there is no export option labeled "Merge" - do you mean the option for "Weld vertices along edges" ? That controls whether faces on either side of a joined edge will have their own separate vertices that are stacked on top of each other or whether the faces will share a single vertex. There's some illustration of that in the help file, see the section labeled "Weld vertices along edges option:" here: http://moi3d.com/3.0/docs/moi_command_reference11.htm#meshdialog


> Something is also unclear for me, should we consider joined surfaces the same as when
> they are displayed as one surface, or as a solid ?

Sorry I'm not sure if I understand this, but basically you can join several surfaces together at places where the surfaces have edges that touch each other. If you have several surfaces joined together in that way such that they form a completely enclosed skin then that will be considered a solid. If it has any empty areas in it so that it's not a solid it will be called a "joined surface".

Joined surfaces (and solids) will have extra work done at mesh export time to ensure that there is one single unified mesh vertex structure along the joined edge, to make sure that the generated mesh does not have any cracks between pieces. If 2 surfaces get meshed which are totally independent from each other rather than joined to each other it's easy for them to get slightly different vertex structures along the edges (due to different refinement in the surfaces that come off the edges), and that will result in cracks between the different independent surface pieces.

Additionally when you have a joined surface the polygons for the entire joined surface will have a consistent normal direction. If it's a solid it will additionally have the normals pointing to the outside of the volume. If it's not a solid it will have a unified normal direction but which specific side will be the positive side can vary depending on the particular way you constructed the object. There is a "Flip" command which can flip the positive normal direction for a non-solid joined surface: http://moi3d.com/3.0/docs/moi_command_reference10.htm#flip


> Sometimes the edges can be joined to a solid or a unique surface, sometimes not,
> what is the rule have in mind there ?

Well, usually you will want to join surfaces that are sitting next to one another so you'll get no cracking and a unified normal direction at mesh export time. It can also be a bit easier to have things be solids rather than open surfaces because it then also locks down the positive normal direction automatically as well, but that does not really matter if you just turn on double-sided rendering in your rendering program.

- Michael
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 From:  delic
7388.19 In reply to 7388.18 
Thanks a lot Michael.

You understood perfectly well what I meant, I'm french speaking, so I make some mistakes in English.

And yes it was about the "weld" option, not merge. Inside one 3d package it can be confusing, weld, merge, join, collapse, etc ... so between different software it's even harder to understand sometimes, it can be confusing.

For the open edges, it can be useful to let them open during export sometimes, so it's good to have an option to weld or not, joined edges in this case.

For the "joined surfaces" vs "solids" I will try to build a simple shape with different methods, to figure out how it works, when the rebuild command make sense for ex, to have clean geometries that are commands friendly.
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