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 From:  David marmor (DMARMOR)
6617.1 
Hi,
I'm trying to learn MOI and I found it really entertaining, not the usual word I use when building complex surfaces as I'm used to polygonal modeling.

I choose to make a simple object, a great helmet
http://www.ageofarmour.com/instock/images/greathelm-08-side.jpg
I think it has all the quality needed to start my learning. And I did one in polygonal modeling and that was a tricky object to made, because of the many holes it has in it.
Hard to get a perfect surface when holes are made in a curvy surface.

I've attached the curve I made to build this shape, but I can't build them correctly, can you tell me if I am doing it right or if I am missing something?

Thanks

EDITED: 8 Apr 2014 by DMARMOR

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 From:  Michael Gibson
6617.2 In reply to 6617.1 
Hi Dmarmor, welcome to MoI!

Check out here for some links to discussions and general tips for people who are coming from a sub-d / poly modeling background:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

One big difference is that booleans and cutting operations are a primary way of doing things with NURBS modeling, and you want to work more with 2D curves to generate a lot of things rather than squishing things around with 3D point cages like you would with poly modeling.

If you find yourself trying to squish the points of a curve around in 3D, it's often a sign that area should be coming from an initially extended and more simple object with the final edge coming from a cutting operation, rather than trying to directly model it as you're showing there.


So for example probably do either a revolve or maybe a loft to build the initial shape, and to start with just ignore the bottom curved edge, build an extended piece to start with something like this (here a loft between 3 ellipse curves):



Then to customize the bottom part, draw in a new side profile curve something like this:



Then select the main piece, run Construct > Boolean > Difference, and use the side profile as the cutting object. That will divide the main solid into 2 pieces leaving the side walls of the side curve to form a sort of "imprint":






Usually to make things cook along quickly you want many of the final 3D edge curves of your model to be formed by this type of intersection or cutting operations, you should try to primarily draw 2D curves as much as possible and that's sort of the key thing to making things happen fast. And not only fast, it will also tend to make smoother results because irregularity in your construction curves will usually leave some sort of side effect in the surfaces constructed from them, you get better quality by making more simple surfaces and then more detailed outlines just come from carving the simple surface rather than a direct part of the initial surface construction...

It tends to be easier for poly modelers to recognize that an interior hole should come from a boolean operation, but it takes a bit more practice to get used to outside shapes coming from them too, that's the part to get used to. The link above goes over this concept with some other cases as well, the thing to get used to is sort of like "build extended and then cut". It's a very different type of strategy than what you use for poly modeling!

Hope this helps get you pointed in a good direction!

- Michael

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 From:  David marmor (DMARMOR)
6617.3 In reply to 6617.2 
Hi Michael,

There are still a lot of things to read. I continue experimenting with my little helmet.
After posting I did the same thing, using loft, for constructing the shape.
But with this I can't keep the curvature from the side line, it is bended at the top and then go straight down.

The revolve seems to just use 2 curves, and because of that I have to choose between the starting circle or the end circle, what I would like it to have a blend between these two.

So I decided to make a network of curve, I duplicated the profile curve and build a network with these curves. It almost work but if you can do a kind of revolve by selecting the first three curves I selected that would be faster and easier.
Now I have an other issue, I want to have a sharp indent where the profile curve start the bend but I was unable to do it.
How would you approach this?

Personnally my strategy is to keep the less curve and edit point possible to allow for easy manipulation and having the smoothest resulting surface.
Coming from poly background the more point you have the more lumpy your surface can become and it make your modification more complicated in the end.
I really want to be able to modify on the fly my shape to be able to accomodate to any design change.

Thanks

EDITED: 9 Apr 2014 by DMARMOR

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 From:  Michael Gibson
6617.4 In reply to 6617.3 
Hi Dmarmor,

> Now I have an other issue, I want to have a sharp indent where the profile curve start the bend but I was unable to do it.
> How would you approach this?

I'm sorry but I don't really understand this part.... Could you maybe circle the area on the helmet that you're referring to or show me on the original helmet picture what it looks like?

- Michael
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 From:  Michael Gibson
6617.5 In reply to 6617.3 
For an indentation, maybe you're looking for a technique like the one shown here? :
http://moi3d.com/forum/index.php?webtag=MOI&msg=4880.1

- Michael
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 From:  David marmor (DMARMOR)
6617.6 In reply to 6617.4 
Sorry I used the wrong term, I wanted a sharp edge where the edge start to change its direction to be vertical.
I circled the part I'm refering to. I think I can detach the shape in two part but what if I want to tweak how sharp the corner is?
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 From:  Michael Gibson
6617.7 In reply to 6617.6 
> Sorry I used the wrong term, I wanted a sharp edge where the edge start
> to change its direction to be vertical.

It depends on the particular method you're using for the construction - for Loft like I showed above I used the "Loft Style = Straight" option. For something like Network you would either make the network in 2 separate passes for the top and bottom sections, or you would make your network curves come to a sharp corner point on that spot.


> I think I can detach the shape in two part but what if I want to tweak how sharp the corner is?

Well, again it depends on the particular surface construction technique that you're using but typically the entire shape of the surface is defined by the shapes of the profile curves used to construct it, so if you want something that bends more sharply you make the curves that are used for it bend more sharply and so forth...


With NURBS modeling you usually put most of the effort into arranging the curves, then the surfaces are constructed to follow that curve structure. You don't typically try to tweak a surface after it's been created - you usually try to get your curves set up so that the surface gets created with the desired shape right in its construction...


- Michael
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 From:  David marmor (DMARMOR)
6617.8 In reply to 6617.7 
Thanks, but if you keep the curve used for your construction you can modify the resulting shape isn't it?

An other thing, I can't find a way to make a rail revolve using two rail curve, is it possible?
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 From:  Frenchy Pilou (PILOU)
6617.9 In reply to 6617.8 
<< An other thing, I can't find a way to make a rail revolve using two rail curve, is it possible?
No for the moment! :)
---
Pilou
Is beautiful that please without concept!
My Gallery
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 From:  David marmor (DMARMOR)
6617.10 In reply to 6617.9 
Ok thanks ;)
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 From:  Michael Gibson
6617.11 In reply to 6617.8 
Hi Dmarmor,

> Thanks, but if you keep the curve used for your construction you can modify
> the resulting shape isn't it?

Yup, that's the history feature where after you've created a surface you can edit the curves that went into it and it will recalculate as long as you haven't done some other type of edits on the surface.


> An other thing, I can't find a way to make a rail revolve using two rail curve, is it possible?

Not in rail revolve, but you can do a Sweep with 2 rail curves.

- Michael
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 From:  David marmor (DMARMOR)
6617.12 
Hi, still learning MOI and I have a couple of questions for you ;)

I'm still on the same subject and try to grasp the concept.

I have a little issue when building my surface that I can't resolve, there is a little bulge visible.
How can you avoid this? you can see it on the bottom front panel.
I rebuild my curves but it is still there.







Thanks

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 From:  Michael Gibson
6617.13 In reply to 6617.12 
Hi Dmarmor, could you please post the 3DM model file ? That would help me to take a more in depth look at your actual geometry, it can be easier to answer questions when I'm able to look at your actual objects rather than only a screenshot.

It's hard to say from just a screenshot, but it's possible that what you are worried about is a display artifact and not really an intrinsic part of the real surface. In order to display a surface on screen it has to be broken down into triangles, and in a curved area if there were not a lot of triangles created it can leave a bit of evidence of the triangulation in the on screen display.

One way to see if that is the case is to do a test export of your model to a polygon format like OBJ format, and then crank up the density there and set the display mode to be shaded and that will show you a lot more detail on the actual surface form and minimize display artifacts. That's the kind of thing that I would do over here if I was able to examine your model file.

- Michael
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 From:  David marmor (DMARMOR)
6617.14 In reply to 6617.13 
Unfortunatly I'm using the trial with no save so I can't save this file.

And I finally I solved my issue, the bulge was visible because of bad curve construction.

If I can add a question, is it possible to have a jiggle parameters for the array to add some imperfection in the placement of the objects?

And an other thing I didn't find, how do you project your curve on one side only? Currently it project through the whole object and you end up with two curve, the same things happen with the boolean diff, the hole is occuring through the entire object and I would like to have a control on the depth of the cut.
Thanks

EDITED: 12 Apr 2014 by DMARMOR

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 From:  Frenchy Pilou (PILOU)
6617.15 
<< If I can add a question, is it possible to have a jiggle parameters for the array to add some imperfection in the placement of the objects?

You can use some random selection of something ;)

Take a look here at this thread ;)
http://moi3d.com/forum/index.php?webtag=MOI&msg=3974.1


And for jiggle look at this one
http://moi3d.com/forum/index.php?webtag=MOI&msg=6447.1

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 From:  Michael Gibson
6617.16 In reply to 6617.14 
Hi David,

> If I can add a question, is it possible to have a jiggle parameters for the array to add
> some imperfection in the placement of the objects?

There isn't currently any mechanism for doing this - it's usually not very feasible to get good results by just randomly jiggling control points around, especially if the control points are not completely evenly spaced it's easy for some of the points to have a more pronounced impact on the end result.

MoI is overall itself not focused on generating organic type shapes, usually you would want to bring your model into a different program that is focused on that type of thing to add those kinds of details, like import it into 3D Coat or ZBrush.



> And an other thing I didn't find, how do you project your curve on one side only?

You would usually just generate the projection on both sides and delete the one that you don't want. Also if you're trying to project for the reason of cutting a hole in an object using Trim, Trim has projection built into it so it's usually better to not do the projection as a separate step. When you pick which areas to discard in trim it will only use the projections surrounding those pieces.



> the same things happen with the boolean diff, the hole is occuring through the entire
> object and I would like to have a control on the depth of the cut.

For controlling the depth of a boolean, do an extrusion of your object to your desired depth and then use the extrusion as the cutting object instead of the curve as the cutting object. In the future I do want to add a "limit depth" option to the booleans that would handle this easier, but for now you just construct an extruded cutting object.

- Michael
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 From:  David marmor (DMARMOR)
6617.17 
Thanks for the answers.
About the jiggle I think it is a very specific demand and it was not about the placement of points but of curves or objects.
The great helmets have holes in front, but these holes are not made by a machines but by hands.
So what I wanted to do is to make an array of circles along curves to place the cutting objects, but I didn't want them to be at the exact same spacing.
I wanted to introduce some small differences in the spacing, not really noticeable but still present. That help to make it hand made.
But in most case I will use MOI to make "industrial" objects so that is a really specific case. I just don't have to build my medieval armours in MOI :D

About the scripts I'm not sure it will work in my case, but I found some interesting scripts along the way.
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 From:  Michael Gibson
6617.18 In reply to 6617.17 
Hi David - jiggling entire objects a bit is a lot more feasible than trying to jiggle curve control points. Check out here for a randomize plug-in which you can set up which will let you do some random movement, scaling or rotation on objects, it should work to add so me non-uniformity to your cutting holes:

http://moi3d.com/forum/index.php?webtag=MOI&msg=5416.5

- Michael
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 From:  David marmor (DMARMOR)
6617.19 In reply to 6617.18 
Thanks Michael,

The script will do the job, an other usefull tool to use.

Still learning Moi, and still liking it, not that it goes along smoothly everytime but some headaches I could have with polymodeling are so simple here.
But I have to admit that sometimes its simplicity make things difficult, you have to make many action to get a simple result.
For example I had an hard time to cut a surface from a projected curve, I was not able to do it so I had to make a shape from the original curve and use it for a boolean diff.
But I will use this method more often as it seems to be the way to go. The downside is that it need a lot of planning and doesn't allow for a streamlined creation.
Many time I had to redo my shape because I made a mistake while constructing my shapes.

This for example, I build the flat shape from a curve but build only one half. I then made an offset shell to get my thickness but the result was not correct at the middle after doing a mirror.
There is a way to fix that or do I have to rebuild my curves? What I had in mid was to take the border edges and align them at the center and then merge the resulting shape. It's possible to do that?


Sometimes when I have finished my shape and I need to make a forgotten operation I'd like to retrieve the curves from my shape, is it possible?
I'd like to have just the exterior line to be converted as curves, but I didn't find a way to do so.

An other thing about this helmet is that I wanted to have each panel overlapping each others, like the real object. I suppose I have to do it with my curves or I can do it when my solid are built?


Here is the short lived result as I'm using the saveless version ;)
Not really happy with it but that's just an exercise and I learned a lot. That's a really simple object but it was a hard time.





One last question, is it possible to keep the object used to create a boolean and edit them while still seeing the change in the resulting boolean?
Something like meshfusion, you have a plane cutted by a cylinder and if you scale your cylinder you see the resulting boolean changing, same for any kind of boolean operation?

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 From:  Michael Gibson
6617.20 In reply to 6617.19 
Hi David,

> For example I had an hard time to cut a surface from a projected curve, I was not able to
> do it so I had to make a shape from the original curve and use it for a boolean diff.

If the curve became non-planar after it was projected, that would cause that type of effect - boolean difference can only directly use 2D planar curves as cutting objects, they become extruded as a process inside the boolean.

If you want to only cut some limited distance into an object instead of all the way through then that is normal that you would build a shape from the original curve and use it for the boolean, that's the process for doing that...



> Many time I had to redo my shape because I made a mistake while
> constructing my shapes.

As you gain more experience these types of mistakes will become less common.



> This for example, I build the flat shape from a curve but build only one half. I then made an offset shell
> to get my thickness but the result was not correct at the middle after doing a mirror.

Yeah, that's just how offset geometry works - the offset surfaces generated from individual surfaces will only touch each other if the surfaces are smooth where they meet up.



> There is a way to fix that or do I have to rebuild my curves?

You can try to join the surfaces together before you do the offset - that will then make the offset surface get extended to fill in the missing area.



> Sometimes when I have finished my shape and I need to make a forgotten operation I'd like to
> retrieve the curves from my shape, is it possible? I'd like to have just the exterior line to be converted
> as curves, but I didn't find a way to do so.

You can extract edges by selecting them and using Copy/Paste to duplicate them, the pasted result will be separate curve objects.



> An other thing about this helmet is that I wanted to have each panel overlapping each
> others, like the real object. I suppose I have to do it with my curves or I can do it
> when my solid are built?

You can move the panels around after you have created them. But if the overlapping involves some kind of shape adjustment rather than just movement alone then you would want to have that set up with your curve structure instead.



> Here is the short lived result as I'm using the saveless version ;)

It turned out well!



> One last question, is it possible to keep the object used to create a boolean and
> edit them while still seeing the change in the resulting boolean?

No, not currently but that is something I want to add in the future with a deeper history mechanism.


- Michael
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