Week 2: NURBS

hey all!

As expected this week was tougher than last. This week was the 'dreaded' surface modeling (a.k.a NURBS) week. We had Steve McClure again for this class. His advice to use was that NURBS can be "a fickle mistress", both seductive and alluring, but often frustrating..haha. NURBS is just an funny acronym for Non-uniform rational B-splines. huh? And all that nonsense means is NURBS surfaces and curves are infinitely smooth, since they are mathematically described. Just like Adobe Illustrator bezier lines or postscript fonts. NURBS are mostly used in product and automobile design since they can create perfectly smooth surfaces which are needed for prototyping. All cars, cellphones, etc.. start out as CAD models and are then made into NURBS models.

So this week, we us explored various ways NURBS can be used both in product viz as well as in the entertainment field. Keep in mind the focus of each class is just that subject, so for modeling we dont worry about lighting/texturing, etc. Just the shape/form. For our first test, we created a hairdryer using a technique called "lofting" or sometimes called 'sweeping". It's just like the technique used in shipbuilding where the boat's surface is creating by laying down and conforming the planks to the 'hulls'. In the same way 3d surfaces are created my laying a surface over "curves". See the cross sections of the boat in the picture at the top? the surfaces are created by spanning those curves. Nuff said.


So for the dryer we used that same technique and also some others like 'revolving" (rotating a curve shape in 360 degress to make a surface) and filleting, another woodworking term. We also projected curves on the surface of the dryer, as well as 'trimming' those surfaces after the fact. After all was said and done, I have to say it's a cool way to build stuff. When NURBS does work, its really cool. When it doesn't..NOT so cool. Here are some quick renders of where I'm leaving this one for the moment.



The next day we did a stainless-steel sink using a technique called 'template surfacing'. With this one, you build the different levels of an object as templates (the topmost suface, the cutouts for the sink basins, then the sink bottom, etc..) and then create the rounded transitions to connect them all (fillets). Here are some screen caps to show the process...

starting with drawing curves of the templates at different heights...


and then connecting those curves with lofting, planar surfaces, and fillets.


here is kind of what it looks like when done the modeling. One cool part was making the washing board with those ridge shapes. We used a tool called "soft modifcation" which allows you to pick a point on the surface and pull it, but with a falloff in the surrounding affected area. Makes the surface kind of 'stretchy', like clay. You can see in the image below, the yellow areas a most affected by the point i picked and the more red/darker they get the less they will move. Just pulling up 1 point on the square surface i made for each rib created that shape. it would be much harder otherwise!


Lastly we did a concept car, which kind of incorporated all the methods we learned in the week. I liked the exercises, but it was frustrating a bit not to be able to take them further. The pace is just too fast to get hung up on that, so I'm trying to just get the concept down and maybe later go back and refine them at some point.

The car was done in a similar way as the boat described at the beginning. Just laying surfaces over curves with lofting, as well as all the techniques we learned. I really hope to go back and finish this one cause i think the end result could be really nice. Here is a turntable from my screen.



Well, that's enough for one week, whew! I hope I can survive the whole course...hah.
Next week is polygon modeling (my favorite) so that should be fun.

Peace!