Polygons, meshes, NURBS, solids. What's the difference?

[Mattheng]

I am having a very simple attempt at some basic 3D modelling and have absolutely no idea which of the above methods (objects?) I should be using.

What are the pros and cons of each?

Does Vectorworks handle one better than the others?

Do other programs prefer one or the others?

The 3D Powerpack looks intriguing but I'm really not sure where to begin...

Matt

[mike m oz]

GENERAL

- 3D Modeling in Vectorworks manual: http://www.vectorworks.net/training/guides.php

- Movies: http://www.vectorworks.net/library/index.php

POWER PACK SPECIFICS

- 3D Power Pack Movies: http://www.vectorworks.net/3Dpowerpack/qtexamples.php

- 3D Powepack Tutorials: http://www.vectorworks.net/3Dpowerpack/tutorials.php

[Kizza]

Some generic info:

Mesh Info

NURBS Info

Polygons are closed shapes which can represent 2D data or 3D data. 3D data can be extruded to form solids.

[Kevin McAllister]

Hi Matt,

You've asked a very good question, one that I've never seen answered very well. I wondered the same thing a few years ago when I dove into the deep end and started 3D modelling everything. Because I do design work for theatre and events, I've modelled a lot of unusual stuff. Here's what I can tell you from my experience -

- when I started out I mostly worked with either solids (extrudes, solid additions/subtractions) or NURBS objects. Each has their advantages. Solids behave well and render cleanly. Solids are also necessary if you want to section objects and have them show up "solid". NURBS are essential for many shapes that use curves. NURBS create both curves (3D lines and polylines) and surfaces (filled shapes). But NURBS show up as pieces or facets in some rendering modes.

- I've only recently investigated 3D polygons in greater detail. Polygons are efficient unless you have a lot of them. Many other 3D modellers use polygons exclusively. Vectorworks doesn't really work with groups of polygons in the same way, so unless you're importing from other programs you're less likely to do much polygon modelling. A 3D polygon is only a surface anyway (usually a triangle or quad). Any object made of polygons is basically an empty shell. If you section it is shows up empty.

- A mesh seems to be a connected "blanked" of polygons in VW. I can't say I've used them much if at all.

I would suggest starting with solids first. Most simple objects can be created by adding and subtracting solids. Extrudes are the easiest in the beginning since they are created using 2D shapes you're probably already familiar with.

From there I would investigate NURBS. The NURBS tools in VW are extremely powerful but not particularly user friendly. Some NURBS tools will interact with solids and solids can always be converted to NURBS if needed. Often collections of NURBS can be combined back into solids using Stitch and Trim, but not always.

Hopefully this helps a little as you get your feet wet in 3D.

Kevin

PS. I've added a file comparing objects as solids, 3D polygons, and NURBS. I've opened the tops to show how the 3D polygon and NURBS objects are hollow. Notice how the 3D polygon objects have black areas, that's because VW is drawing the outline of each small polygon. You can reduce the conversion quality for less polygons but then your curves begin to appear facetted. Notice how smooth the NURBS curves are since they are mathematically derived.

Edited September 18, 2012 by Kevin McAllister