Full Version: Newbie Questions

Hi everyone, after spending the first day of the trail version yesterday I was pretty much sold.
I'll ask any of my questions in this thread.

So I'm new to CAD / spline modeling, I did a bit of low-poly and subdivision modeling in the past, mostly out of curiosity.
I've not yet watched or read any tutorials, I found the interface to be very intuitive so far, so I've been happy just experimenting.

Here's a boat-like shape, even though the corner control points are in the same position there's a seam showing up.
Why is this and what are some ways to solve/avoid it?

Image Attachments:
crack.png 

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Hi peter,
In NURBS modeling, those arent called "corner control points"....

Curve Points have additional properties minimally referred to as "weights", which affect surface structures.

"Patch modeling" like you would do in a poly app is a more low level, advanced technique. To learn NURBS and avoid this initial road block, you'll want to think about modeling in larger more contiguous terms and using booleans as a means to shape things.

A "boat" would be an advanced model to start on... maybe start with something like a bowl or a cup, then work your way up...

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Hoi Pieter,

Uit Nederland neem ik aan? :)

As Burr stated NURBS modeling differs fundamentally from polygon subdivision modeling. NURBS modeling is usually about constructing surfaces using a structure of perfectly aligned / adjacent curves, or using Boolean operations to subtract, add or interesect solid NURBS primitives (contrary to polygon modeling, Booleans are very useful in NURBS modeling). Tweaking the control points of the resulting NURBS surfaces is something I usually avoid. In stead, I adjust the curves and recreate the patch from them if necessary (if MoI's History is active, then the surfaces will update in realtime when you adjust the source curves).

Check out the Construct section of the MoI reference manual for several different options for creating surfaces from curves and NURBS objects using Booleans:

http://moi3d.com/3.0/docs/moi_command_reference7.htm#Construct

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Thanks, I'll just need to go through some tutorial series I guess.

I really enjoy patch modeling though, I was assuming the "control" points were the 3D analogue for the ones I would find for quadratic bezier curves in a 2D app. But like you mention, it appears to work with a concept of weights. Is there any article explaining how the splines are weighted? Understanding the algorithms involved usually makes things click for me.

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Vlaming!

Yes, CSG is the spawn of satan in polygon land, I'm sure I'll learn to love them with time. Time to RTFM :)

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Hi Pieter,

> Is there any article explaining how the splines are weighted?

http://digiitalarchfab.com/portal/wp-content/uploads/2011/03/Nurbs-Curve-A-Guide-for-the-Uninitiated.pdf

but it's pretty math heavy. Weights are primarily used in NURBS modeling to get exact conic sections like arcs, circles or ellipses.

Usually the main technique to get pieces to align is to construct them from a common base curve, not to manipulate surface control points like that.

Also as others mentioned using booleans and trimming is usually the main strategy to target rather than something to avoid like it is in polygon modeling. Another facet of this is often times it's good to build things out of longer extended pieces and cut pieces away rather than building a surface directly to some complex boundary. So it's really quite different.

There are some tips for people coming from a poly modeling background here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

- Michael

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Vlaming, ah, dat doet je alleen maar stijgen in mijn achting. :) Ik ben in Brussel geboren.

Succes en een fijn weekend!

[Sorry for the Dutch / Flemish têtê-à-têtê, guys ;) ]

Metin

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visualization • pixel art • illustration • 3D design — https://metinseven.com

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Hi Michael,

Interesting stuff, will certainly try to wrap my brain around it! Splines give me a warm and fuzzy feeling.

On another node, I just recently switched from Windows to a Macbook and I noticed the image looks a bit pixelated. This is on a retina screen, I'm not sure this is expected behavior in that case, I do think it looks a bit unsightly. I also noticed some WINE dialog on first start, which I cancelled and I haven't been prompted again.

Would be nice if I could run at native resolution, though not a make or break issue for me.

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Hi Pieter, the pixelated Retina display will be fixed in MoI v4. One of the big changes for v4 is that it's now a native build for Mac and isn't using the Wineskin mechanism anymore. Among the various little glitches that are solved is that it uses the native resolution on Retina displays now. The current v4 beta is available to existing users here: http://moi3d.com/beta.htm

- Michael

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