Having used Blender for several years as a tool for adding effects and titles and the like to my videos, I finally decided I should take a serious look at modelling. I picked up the book “3d Graphics and Animation (2nd ed.)” by Giambruno and I’m following along the tutorials. One of the techniques used a lot is skinning (lofting) multiple mesh shapes. This is one of the very few features missing in Blender. I know that I can do this using NURBS surfaces, but I haven’t been able to manipulate the NURBS into the right shapes. What I’m trying to do is shown here:
In order to do this with NURBS I have to add a NURBS suface circle, increase the number of control points in order to approximate the square, duplicate 3 times moving the new NURBS into the correct positions, and then changing the right-most (in this picture) two NURBS back into circles.
It’s the last step that’s giving me the problem. First, it’s very hard to get a true circle by manipulating the control points by hand. I’m wondering if there’s a better way of doing it. Secondly, when I get a good approximation of a circle and the then skin the surface everything gets pulled into a more-or-less square shape; the control points for the circular shapes are affected by the control points for the square shapes.
Is there a better way of doing this? Note that some of the other tutorials require skinning a much more complex shape, so trying to animate through a lattice or other simple manipulations and using dupliframes won’t suffice.
I think I get your point, you start out with a NURBS circle… then subdivide it once to get the rectangular shape… duplicate it for the lower part…
After that again a NURBS circle without subdiv… dupe that one for the top…
The problem is that while surfacing (after joinging the shapes with CTRL J)… the transition between lower (rectangular) and top (circular) part doesn’t work… because the reslution doesn’t match…
When you subdiv the circle… it affects the shape and I agree that it’s stupid to try to manually recreate the circle that blender just made into a rectangular shape…
Somehow you have to be able to set the resolution of the circle without blender affecting it’s shape.
I’ve tried different ways now and didn’t come up with a solution… I hope that someone on the forum knows how to solve this though because it should be very basic…
I don’t really understand why you chose to increase the number of control points for such a basic shaped object. (Perhaps, you are trying for greater precision?)
Why not just start from the Surface Nurb circle end, extrude a few times for the circular part, a couple more times for the square part, then select all 8 of the “corner” control points of the square part and then set their weight to about 10. Then select the edge of the circular end, extrude and scale to 0 to close the end.
Some Hot Keys that should help:
Select a control point, and press:
[N] - shows the location as well as its weight,
[Shift_R] - selects a row, press again to switch direction
(You can then select another point and press Shift_R to select 2 adjacent rows),
[W] - allows you to subdivide or switch direction (If the curve is 'inside-out),
[E] - extruding,
[X] - deleting stuff.
Using these you can find the control point weights of the circular part, then select the pre-set weights in the Edit Buttons Window, and assign them to the square parts, if you wish.
Some more information about weight at IAmInnocent’s site:
It’s true that Blender’s NURBs implementation is very basic. It should improve a bit when the person working on adding the NURBANA code has time to do so. ( I believe the person is busy with university now ).
Blender’s emphasis to this point has been improving the mesh (SubSurf) tools.
I don’t really understand why you chose to increase the number of control points for such a basic shaped object. (Perhaps, you are trying for greater precision?)
in order to transform a circle immediatly in the rectangle…
Using these you can find the control point weights of the circular part, then select the pre-set weights in the Edit Buttons Window, and assign them to the square parts, if you wish.
Okay so this means that one won’t get a message from blender that the resolutions don’t match while surfacing ?
Alright… I have discovered my mistake… I was selecting all controll points and setting their weight… indeed Surt… I needed to select the corners and set weight for the effect to work … thanks…
Yes, I’m getting this (in between the moments when my system isn’t in pieces all over the floor while I rebuild it). Since you (md01) most adequately expanded on my original question I didn’t really have a lot to add
I did exactly as you did; subdivide for the making the circle into a square. The only difference is I replicated that square 4 times and then manually pulled the last two into more-or-less (less I think) circular shapes so that I had the same number of control points.
I also made the same mistake of trying to increase the weight of all the control points rather than just the corners.
My system is pretty much back together and I’m going to try again. I find that I have difficulty shaping NURBS into what I want (lack of modelling skill really showing here) but I might be able to hack it.