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You calling ME a NURBS ?

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#1 Scythar


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Posted 26 December 2007 - 11:49 AM

Seen the time spend for this first very little tutorial, i think this is going to take forever...
My intentions are to teach you about splines and NURBS...

Lets start:

NURBS = Non-Uniform Rational B-Splines (hey, dont shoot at me, i didnt invent the darn name!)
Basicly, its an alternative way of modeling, most of you allready did at some time or another. The standard way of modeling would be "polygonal modeling", where you work with polygons (the building blocks of 3D shapes).
Here, with NURBS, you work with "source objects" (splines) and C4D will attempt to generate the polygons necessary to make the object. This allows for smooth objects (B-splines are very smooth) and gives a great flexibility: you can always alter the splines to alter the entire form.
There are off course some drawbacks. Among others: C4D doesthe work for you, so its not always 100% predictable what the endresult will be, and if an object is part of a NURBS, you have no control on a polygon-by polygon basis...

These are the NURBS-generators:

Those marked with blue are the classic (real) generators (those who need splines as a child to be able to generate the polygons), Those marked in red are both special ones and will be explained in this tutorial (in several parts).
Part I of the tutorial is about the BezierNURBS, which basicly doesnt need anything and lives by itself. In part II (in bout 3 years :) ) i will try to explain bout HyperNURBS, which needs a polygon object as a child instead of splines.

Thus, those marked in Blue will be subject of a entirely different Tutorial (Part III) in bout 20 years...
Thes are the splines bdw:

to be continued...

Edited by Scythar, 26 December 2007 - 11:59 AM.

#2 Scythar


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Posted 26 December 2007 - 12:04 PM


Lets make one right now...
go to the NURBS-generator menu and click the Bezier NURBS icon.
Whats the result?

Thats wright, a plane...
Whats so special bout a plane i hear you say (admit it, i DID hear you)
Well, its not an ordinary plane which exist out of normal polygons

sry, rest follows tomorrow,
children at home and its war :tiphat:

Lets take a look at the attributes manager:

The properties:
Subdivision X and Subdivision Y are the amount of polygons (which you can NOT select !!!)the NURBS-generator generates, and most of the time it is only important to increase this, IF you're planning to convert it to an editable object later on (or you are going to give it a lot of detail). Smoothness is usually enough as it is.

Grid Points X and Grid Points Y are a grid you create on top of the object with points, which are basicly the control points of the plane you CAN select with the point tool to alter the shape of the plane (like B-spline in the splines menu)

We will show the effect now...

First check your settings:
Select the point tool, and then the rectangular selection tool;
Then go to front view and select the second column:
PointTool.jpg rectSELtool.jpg

Now, while holding down the shift key (to add to the selection) select every other column (meaning columns 4, 6, 8, 10 and 12).
Then go back to the perspective view.

Click on the blue axis (Z) and move it towards you for about 20 units --> That would be a curtain :) ...

And since the generated polygons are not the same as the gridpoints, you can change the Subdivisions, without loosing the shape completely. Try it!

Edited by Scythar, 27 December 2007 - 07:43 AM.

#3 Scythar


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Posted 27 December 2007 - 07:55 AM

Animating the curtain:

Since you dont loose the shape you can animate the curtains (opening and closing). Try the following:

  • Make sure you are at the first frame
  • in the attributes manager, click on the coord. tab to open it (if you want the other one also open, shift click instead)
  • AttributesManagerSettings3.jpg
  • ctrl+click on the little circle in front of S.X (meaning: scaling along the X-as, for us this means opening or closing the curtain). This creates a keyframe (circle turns red), with these settings;
  • Go to frame 45 and then go back to the attributes manager and change the S.X setting to f.ex. 0.5; now again ctrl+click on the (now open red) circle again.
  • Goto frame 90 and repeat, readjusting the S.X back to 1 (dont forget to ctrl+click !)

Play the animation.

#4 Scythar


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Posted 27 December 2007 - 08:02 AM

Some more experimentation:

Back at first frame (no anim here)
  • Go back to front view and select every other row now:
  • selectEveryOtherRow.jpg
  • Then go back to perspective view and do the following:
  • drag the blue axis (Z) 20 units to the back;
  • drag the green axis (Y) 30 units to the top;
  • invert your selection
  • Invert_Selection.jpg
  • drag (the inverted selection) with the red axis (X) 30 units to the right.

The units are not so important, and the result is not much, but at least you understand the effect now and how easy BezierNURBS works.

Endresult (quicky)

Edited by Scythar, 27 December 2007 - 08:03 AM.

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