Sculpting with Force

As mentioned in my resources page, one of my most significant go-to books for drawing is the Force series, illustrating brilliantly how throughout living organisms, there is a rhythm, a path where metaphorical ‘force’ ricochets from one part of the body to the next.  Keeping this in mind, I decided to see if there was a way to more directly translate or ‘sculpt’ in CGI modeling software (Maya, for the purposes of this entry) this concept, by starting with drawings that were produced using this method, but then arriving at a model by mimicking those methods using standard modelling tools in Maya.

Here’s where I started:

Just a very quickly sketched out leg.  In retrospect, I could have pushed the forces a lot more, but you can still clearly see them sweep from the front thigh through the knee, into the back of the calf, into the heel.

Most modeling tutorials I’ve seen will either instruct the student to start with stock cylindrical objects and continue to push and pull vertices to match the geometry until you’re ready to peel back your eyelids from the sheer inanity, or create one edge loop at a time, bridging the new one with the previous.  It’s an improvement, but a slight one.

I think, however, that I have found a way to more easily construct limbs and bodies for characters relying almost entirely on your sketches in the creation of the geometry rather than hammering stock geometry into your desired form.  At the very least, it should minimize the amount of that kind of irritation.

Anyway, here we go…

I’ve imported the two views of the leg into Maya’s front and Side camera views respectively.  In the Perspective view, that looks like this:
Now, in the Side and Front views, I use my choice of curve tools (in this case, a combination of EP curve and Bezier curve tools to trace the front and back side of the leg in the Side view, and the inside and outside profiles of the leg in the Front view.  You’ll notice that they probably won’t line up the way they should, as the centerline of the limb is not necessarily plumb vertical the way the planes you’ve been drawing your curves on, are.  With a few rotations and translations, you’ll get something that looks like this:

Also shown above are two loops that connect the tops and bottoms of the curves.  These are important for the tool I ended up using to create the surfaces.  Starting with the line towards the back (the heel side) and with curve-snap on, I used the EP curve tool to make the loops, and I moved in a counterclockwise (from above) direction in both.  Consistency in creating the top and bottom loops is critical.
Next, I select the Birail 3+ tool from the Edit Curves menu and set it to the following settings:

Using the general tesselation setting here allows you to build the leg in four surface wedges that have the same number of polys along each edge and have them mostly line up closely enough that they can be merged more easily together in the following steps.  Take note here!  The number of polygons in the U and V directions will be one less than the number indicated in the initial tesselation controls.  So if you want your limb to be 30 units long, enter 31 into the U field.  You might also want to take note at this point of how many polygons you want your limb to be around as this will come in handy when modeling the torso and how many polys around the opening is for your limb to connect into.  We’ll be doing this four times to bring the limb surface to a full 360 degrees before stitching all four together, so take the number in your V field, subtract one from it, and multiply by four.  That will be the number to remember for attaching these limbs more easily later.

Starting again from the place where you started your loops, start the birail 3+ tool and follow its instructions, moving counterclockwise as before, one segment at a time until you’re at the last segment.  Caution!  Have two-sided lighting turned off here, so you can easily detect if the normals of the surfaces you’re creating in these steps are facing outward the way they should be!  Also, in between each use of the birail 3+ tool, make absolutely sureyou remember to delete history on the surfaces.

1/4 done. Remember to check normals and delete history!

1/2 done. Remember to check normals and delete history!

3/4 done. Remember to... yeah, I don't have to say it again, right?


Before you do the last quarter of the leg, Maya needs for the direction on the loops to be reversed (otherwise, it will span the paths opposite to the direction we need).  I can’t say it enough, but make sure you’ve deleted the history on the other three surfaces you’ve already created or when you reverse the direction on the paths, it will affect your work, and when I say ‘affect’, I mean ‘make it look screwy’.
All right, once you’ve reversed the direction on the paths (Edit Curves—>Reverse Curve Direction) then you can finish off the last quarter by repeating the above process going clockwise this time.

We’re in the home stretch now.  If you’re familiar with the basics of Maya, then you know how to combine objects, merge vertices, etc.  It also can’t hurt to make sure once more that all the surface normals are facing outward before doing that.

Once that’s done, and with less than 30 seconds worth of smoothing and sculpting with the surface sculpting tools, here’s the final result, lit and rendered.

Fra-gee-lay. Must be Italian...

Now, you can tell this is still somewhat unrefined, but your starting shape is much closer to the end result than it would be using more traditional techniques.  All the polys are quads, so they’ll deform quite well when animated, and using this method you can plan out your other limbs and the torso ahead of time more easily than (what personal experience has taught me) freewheeling lets you do.

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