I made them with polys...but basically I just want to know how to create such shapes with nurbs. Polys are okay and all, but I feel that nurbs give a cleaner result. I wouldn't use nurbs for an organic shape, there are plenty of better options for this, but for technical, more geometrically based shapes, nurbs seem the way to go.

I'm trying to make the shapes that I choose as diverse as possible, that way, hopefully, all the shapes that I make in future can be boiled down to a few construction methods. I'm still new at nurbs so there's plenty to learn and I think moi makes the learning process much easier.

Cheers.

These are definitely drawing out some really good information!

The key part at the start here is again to break things down into components.

This is a good example that sometimes the components can be pretty subtle - in this case I'd say that there is a kind of underlying surface sheet giving the main form. That's one component. One important thing about NURBS shape design is sometimes you want to focus on just a larger surface sheet and then give it the exact final shape by trimming it down. So sometimes you don't want to focus so much on the outline as the way to start the surface, kind of see the outline as being applied to a more simple surface. Like in this case you would probably go crazy trying to figure out how to sweep or loft that kind of 3-spoked shape directly.

I think that is generally a common way to go down a bad path, I mean trying too hard to construct a surface directly along a boundary where it isn't a natural fit.

So in this case there will be maybe a slightly squished sphere as the base shape (or you could make something more custom by sweeping or lofting), that will get trimmed by a curve projected on to the front of it. Each of the dimples is another component - those will be formed by cutting into the main surface with a small concave shape and then blending them.

Then the outside rim is a sweep along the outer trim curve.

So you can kind of get the feel for this type of "construction" or "drawing" based modeling - I try to construct each piece more by drawing and applying curves and assembling pieces together, not so much by squishing points around. That's the big fundamental difference in technique from a polygon/subd modeler.

But it's getting pretty late over here, I'll do the actual steps tomorrow.

- Michael

> Polys are okay and all, but I feel that nurbs give a cleaner result.

Yeah, for example you've got a very slight dimple in the center there, which seems to me to be not a desired part of the intended design (although maybe I'm mistaken...).

What you should see tomorrow is that doing one sheet as the defining surface will make a kind of super smooth "idealized" quality to some of the parts like this.

- Michael

These are some great tests I must say - they really get you to think nurby-nurby!


As Michael said, I'm seeing a sphere with a portion of the surface extracted - the edges however sound like a loft or something dealing with a profile.

The indentations seems to me look like they should be created seperately (using circles of differing levels and perhaps a profile curve used as a 2-rail sweep? This is then somehow boolean'ed or blended onto the main surface (definitely not sure of that one?)

Figuring this one out would definitely be a great lesson!

-Will

Hi All,

I took a stab at it.. I trimmed a sphere with the curve.
then trimmed the resultant surface with a circle.
then a smaller sphere was drawn in the hole
the new sphere was scaled 1d
it was then scaled up 3d by 10%
the flattened sphere was trimmed by the tri-shape surface
then a fillet was added

I did it quickly so the shapes are off.. I should have looked back
at the image while I was doing it! It sort of gets you there, but
but Michael probably has a smarter solution. ;-)

-Jesse

Edit:

Oops, Michael had already post his method.. it would help if I read the
other responses before I post mine.. sorry.

jdk

Here's the file.

jdk

Hi Michael,
I was playing around with this, is it possible to project a point to a surface? if you project a circle onto a surface you lose the centre ,a point marked is useful
regards Tim.

Tim is right....the hole isn't round..that's why I scaled the sphere up.. actually, it's hard for me to tell from the image, but an ellipse with variable fillet may have been better to duplicate Johnny's model..

j

You should be able to get the center if your center snap is on? Move the cursor near and around the object until you see "cen".

Good questions about snapping points to surfaces - easy to determine however...

Yes, it worked for me.

-Will

Hi Will,

That's a good idea...For what I draw, the construction lines really help a lot to position my curves, so I find if all the object snaps are on
all the time, and the straight snap is also on all the time (unless it occasionally prevents me from doing something),
it's not hard to find the center of anything. So even if a curve isn't planar to the control plane, you can lay down a construction line on the edge of a circle at a quad point, snap to a perpendicular point on the other side and then the mid point of the construction line is your center. I almost never use grid snaps, they annoy me when I forget to shut them off! :-)

-Jesse

Yes I can make it work now, if you have say a circle it will project on its own, straight down, with a point though I have to put in a construction line and then tell it what direction to project, I didn't realize that

Tim.

Thanks, I'm going to try to remember that one..works good.

jdk

Actually isn't there a way to temporarily disable grid snaps?

I think I remember holding down shift one time and it freed up the mouse movement? (Or am I going crazy??) I seem to remember doing that while drawing some curves in MOI one time?...

-Will

About grid maybe this can help you :)
http://moi3d.com/forum/index.php?webtag=MOI&msg=644.3

Hi Guys,

Thanks, but remembering shortcut keys is a little too much for my feeble brain at this point,
but I *would* like to know how you type into the forum with bold print.:-)
Jesse

> Actually isn't there a way to temporarily disable grid snaps?

Hi Will, nope, not by default. You could set up a shortcut key if you want for toggling it on or off though, let me know if you want the script for that.

What you may have seen is that if you move over top of some geometry, you can start to get smooth movement with the "on" snap, that's because object snaps have precedence over grid snaps.

- Michael

Hi Jesse - for bold or italic use these HTML tags:

Type this: <b>This will be bold</b> to get this: This will be bold

Use <i></i> for italics.


And of course you can also do this too, but it can start to get annoying... :) :)

Hi Tim, sounds like you figured out the point projection - yup unlike a planar curve a point doesn't really have a perpendicular direction associated directly with it, so after you start the project command you have to pick 2 points to define the projection direction before it will generate the projected point.

- MIchael

Ok, here are some steps.

Let's make kind of custom curved sheet for the shape of the main body, this will show you how you can tweak the shape more than just using a sphere.

To begin with, I used Curve / Freeform / Control points to draw this curve in the Top view (start with an origin snap):



Then I mirrored that, joined the 2 mirrored pieces, and then turned on points with Edit / Show pts and selected and deleted the center point to fuse the 2 segments into one segment. That just guarantees no creases and a simple construction result later.

Then I switched to the right-side view, and drew this one:



Then again, mirror, join, and fuse segments. That should give you these curves:



Then I selected the curve that was drawn in the top view, and did Construct / Sweep, selected the other curve as the sweep rail to generate this surface:



At this point you can tweak the curves to fine tune the surface shape. This is a pretty straightforward way to create a kind of custom curved sheet to use as the base surface for a form.

Now for the cutting outline - I switched to the front view, and used Draw curve / Freeform / Control points. To help in drawing this one, before I placed the first point I did an initial click, hold-down-and-drag on the origin to create a construction line to use as an alignment snap. Anytime you are in a draw command, you can click, hold down and drag (instead of click and release) to create a construction line. These are useful as snapping and alignment guides, you can do quite a bit of things with them like extend lines, line things up, find the midpoint between any 2 points, etc... In this case I used it to make it easy to snap on to the Y axis. I drew this:



I probably should have spent a little more time on that one, I was just doing this pretty quickly. I think the bottom part is kind of too thin. Anyway you get the idea. I mirrored that, and again joined and fused segments, and then selected the surface, ran Edit / Trim, selected the curve, and discarded the outside piece to create this:



All right, I'll do this one in a couple of installments, I'll return with more on this one later on.

- Michael

I think the second installment will have to wait until tomorrow...

- Michael