Thanks very much for the tutorial Michael, Its nearly midnight here so I will try it out tomorrow morning. I thank you for your speedy reply and tutorial.
Regards
John

O K I couldn't go to bed, I had to play,but I am having trouble getting a planar surface on top of the model? I enclose the file. Like I said, its late and I didnt spend much time in finessing the shape!
Regards
John

Here is a timelapse of a quick tub like you attached, I hope this helps. Just make sure when you create the interior bottom there is an angle towards the drain since your going to make a mold of this.

> I had to play,but I am having trouble getting a planar surface on top of the model?

Hi John, if you switch to the front view and take a look you can see that the top edge isn't planar / flat - it's got a bit of a wave to it. When you were adjusting points at some point you must have pulled one up or down in z a bit, this is easy to do when you are moving them in the 3D view, you sort of need to watch what the label says on the straight snap line that comes out - if it says "z", then you are moving in elevation. If this is getting in your way, you might turn straight snap off while you are doing adjustments.

You can line them up to be planar again by turning on control points for the curve, selecting all the points and then using Transform/Align and switch to the front view and pick in there - a horizontal alignment in the front view will make them flat. Let me know if you want more details on this step.

Or as JTB showed, you can use a different technique to fill in the top even though it is not planar.

But that looks like a good first attempt, that is some progress! You can also see that your 2nd inner points did not stay perpendicular to the axis line - that is why the shape has a crease in it at the mirror line. These can be lined up with each other by also using Transform/Align - go to the top view and use a horizontal or vertical alignment on the 2 ends points.

Let me now if you need any more details about any step!

- Michael

Some more bath ideas - I thought it might be nice to try and carve out a sort of scalloped area for a shoulder/arm type rest. I started with a cylinder, and rotated it into place, kind of stretched it out into an squished ellipse using Transform / Scale / Scale 1d. But it wasn't quite what I wanted, so I duplicated the ellipse edges of the cylinder by doing a drill-in selection to select the edges, then doing copy/paste (you can also do ctrl+drag to duplicate objects, but copy/paste is good when you want to leave them in the exact same position).

Then I made some duplicates of them with ctrl+drag, rotated them with Transform / Rotate / Rotate axis, scaled them around a bit to get these curves:



Then lofted those to make a weird solid slug:



Then boolean difference that slug from the main bath (which I rebuilt again without fillets - usually you want to leave filleting for the end), then filleted after the boolean, to get this:



So this might give you some other ideas on other possibilities - you can create more solids and use boolean difference to cut into your main shape. If you want to make something that sticks out from your main shape, you model a solid for it and then use boolean union to merge it.

I'm not sure if the proportions are very good on this, I'd recommend having a type of rough mannequin type model in there so you can get some idea where arms and legs are going to go in relation to the model, it might be a good idea to have something like that from pretty early on.

- Michael

Oh, and there is usually more than one way to go about doing something - above Grendel shows a different approach where he models more the cross-section of the thickness of the tub instead.

There is no one "right" way, but basically the area that you are most interested in controlling will guide you to where you want to draw your curves to begin your construction.

But still the basic common approach is to draw some curves to define some key areas of your shape, then surface them.

- Michael

Hi Michael
And what about this question
http://moi3d.com/forum/index.php?webtag=MOI&msg=402.10 ?
I am anxious of the answer :)

Oops sorry I missed that one Pilou, give me until tomorrow to answer that one - a quick overview is that there is a process where curves with different numbers of points get points added to them until they all have a common number, which is then the number that is used for the surface.

- Michael

Take your time, it's the week end! :)

Hi Pilou, easy question first:

> Ps Have you a trick for input your numerous images inside the text except a
> Copy / Past address one by one from the download attachment section?

Nope, no trick other than copy/paste right now.


> About the number of control point in the case of a similar family curve than in your bath
> Seems that is not the same number for each curve
> What is the rule? Same number is better or that is no importance?

Well, I'm afraid that this explanation is rather complex, having a lot to do with specific details about NURBS. But here it is anyway....

You can get a cleaner surface if all the curves have the same structure. But there is more to a NURBS curve structure than just the number of control points, there is also a set of values called a "knot vector" which assigns an area and amount of influence that each control point has over the shape of the curve.

"Same structure" for 2 NURBS curves really means the same knot vector, not just same number of points.

If you create a curve by control points, it will get what is called a "uniform knot vector", which means each knot has the same spacing between them, for instance a sequence like 0.0, 0.5, 1.0 . So any 2 curves made by control points will have the same knot vector and therefore the same structure, and that means they combine together well into a surface without having any extra points needing to be inserted.

On the other hand if you create a curve by "Through points", it does not create a uniform knot vector, it creates a knot vector that is spaced different according to the distance between each points. So 2 "through points" curves with the same number of points do not generally share the same knot vector and therefore have different structures.

When you have curves with different structures that you want to combine into a surface there is an automatic method for combining the structures together called "knot insertion" - this inserts a knot value into each curve (also adding a control point for each knot inserted) until each curve has had all the differing knots from other curves added to it so they finally have equal knot vectors at the end.

The problem with this is that it means that the resulting surface sort of inherits the structure of all the curves added together, which in practical terms means it may have an awful lot of control points in it which can be bad. This increase in number of points is avoided if you use same-structure curves so that can be a good way to simplify things.

I do have some plans to work on some simplification and rebuilding of some of the curves when doing lofting that should help do some of this for you automatically.

Sorry that the explanation is so technical, I find this area hard to explain.

- Michael

Well well, Thx for this clear explanation :)
...that is that I have supposed :D

Hi Michael and Pilou,

Without consciously being aware of the particular mathematical concepts
of NURBS, I've found some practical methods to work within their "rules".

Here is my method for making surfaces (from lofts and sweeps)
which are smoother than those generated from individually drawn curves.

For lofts (and sweeps with multiple cross sections), I start out with a circle or
ellipse and shape it by scaling or moving groups of control points.

Then, I copy that curve as many times as needed to do the loft, shaping each curve by turning
on control points and using a combination of moving and scaling (1D or 2D) in symmetrical groupings
until the curve takes the desired shape. For me, it's a lot faster that drawing each one of them, individually.
I don't know how it affects the knot vector arrangement, but it seems to work pretty well.

Without a "Rebuild Curve" tool or the automated function such as Michael is planning
to put into the loft command, it seems like my best solution for now.


-Jesse

Hi Jesse,

> I don't know how it affects the knot vector arrangement, but it seems to work pretty well.

Editing the location of control points does not change the knot vector, so this system works very well - following those steps that you mention, each curve shares exactly the same knot vector so they combine together into a surface very easily with no extra points needing to be added.

- Michael

Hello!

Thanks for making such a great tutorial!

Now to the problem ;p

I was following along well in it until it came to solidify the object. I did everything you said, but nothing happened. I am wondering if its user error (highly likely :D) or program error because of having a different (even newer??) version. My version says Jul-17-2007. Since I am brand new to this program I figure there is at least a little chance that this is a known bug with a quick fix so I had better ask while still trying to figure out what *I* did wrong.

Any help would be greatly appreciated.

Thank you!
Citarra

Hi Citarra, do you mean it would not Shell? Shelling tends to be a fairly delicate operation, if you have any spots on your surface that bend around too tightly shelling tends to only work with small distances.

Can you please post the .3dm file with the surface in it that you are having a problem with? That will make it easier for me to check out what is going on.

You will probably have to alter the surface to be a little less bendy to make it work. Shelling in general is not really one of the most dependable functions in MoI right now, I need to collect up examples where it does not work well so that it can get improved.

- Michael

Any of you guys have or know where i can do a simple robot tutorial?
I finally downloaded the trial version and want to start on something simple
yet something sci-fi-ish since i have alot of drawings for a story in mind.
Thanks for any feedback Morriors

http://moi3d.com/1.0/docs/pod.htm

Have you looked at this one?

Brian

Thanks Brian. I will work on that now.
I'm looking for something simple but have ideas that are in the Wall-E/Old Japanese
style robots style in mind.