In furtherance of last week’s entry, I decided to continue my pursuit of the birail tool in Maya, and it has been something of a revelatory experience. With the discovery of a couple additional tools used in combination with the birail, I now realize the potential to avoid much of the absolute mess that comes with building the model and having the polygons that you’re trying so hard to sew together only to find that they just do not line up, or have a huge discrepancy in the number of polys from one side to the other, forcing you to spend (oftentimes) hours figuring out how to route the edge loops and still have the model move and deform correctly as it should. With all the work at stake, you really don’t want to have to revisit the model’s construction. Here’s a workflow that might help you out if you find yourself in my position.
Before we start, here’s a list of the tools we’ll be using in this entry:
Modify–>Convert–>Polygon Edges to Curve
Create –> Bezier Curve Tool
Edit Curves –> Open/Close Curves
Edit Curves –>Detach Curves
Edit Curves –> Attach Curves
Edit Curves –> Cut Curves
Surfaces –> Birail 2 Tool
As the basis for this week’s example, I’m pulling one of my old characters out for a re-design. It will also be a test to see how effective the technique I outlined with a throwaway model in my last entry, with one that actually may have use for me in the future. Matt Wulf was the first comic character I created. As my drawing experience at that time was almost non-existent, he wasn’t that well designed, and even in his last incarnation, he, as well as the rest of the cast tended to lack visual structure, something I’ve come to appreciate more in the years between. Worst of all, he seemed generic. So here I’ve opened a Maya window and put in a new profile and front view of the re-designed head behind their respective cameras. Of special note, is the emphasis on lines that delineate structure in both views.
Last time, with the leg example, I used the basic side-front camera views to model profiles on the axis, but this meant I still had to reposition the curves for alignment afterward. To skip some of that this time, we’re going to start with a few construction planes. It should also be noted here, that in doing this, it’s essentially taking the lesson from my entry here and simply adding a little bit of planning, and different modeling tools.
So I’ll start with the construction planes. We’ll do the muzzle shape first.
One for the side, one for the front and one for the top. Making the side plane ‘live’, we can switch to the side view, and draw on the canted angle using your preferred method for curve creation (in this case, a bezier curve) thus:
Now, thinking about how high a resolution I’d like to maintain for the model, in this case, about two polys per inch, I see that the coverage on the projected plane surface is about 4×4 inches, so I’ll aim for a poly grid that’s 8×8. But we can’t use the birail tool like we want to until we have at least four curves whose ends all touch. Fortunately, Maya’s Edit Curves menu includes Detach Curves, which will break apart the single curve into multiples wherever we wish to do so, while leaving the ends of each in tangent with the others, as the birail tool requires. Choosing the points to break apart the curve becomes easier with practice, but the general idea is to imagine where the edge flow will merge with your next application of this cycle on a conjoining part of the anatomy. In this case, the shape almost suggests four sides, with corners at the bridge of the muzzle, the corner of the mouth, the tip below the nose, and… somewhere in the sweeping curve on the front of the muzzle? That’s going to take some judgement, but one clue is generally looking in the area of the curve apex. Choose these points by right clicking on the curve and selecting “Curve Point”. If you hold down shift now while clicking, you can select all four points at once, and then click on detach curves, giving us the following:Now to keep track of direction, I came up with my own convention for using the birail tool. That is, I always select top-bottom before left-right. This isn’t a law or even a rule, but just a good principle that you should probably have a convention that works for you and stick with it. There still may be times when you want to switch convention, because the quality of the mesh may differ substantially using the opposite convention. If you’re satisfied with the results of your regular convention though, then you’re good to go. The first pairing of curves you pick will be divided into the number in the “U” field, less one, while the second pairing of curves will be divided into the number in the “V” field, less one. The settings used for the birail tool are covered in the previous entry, for reference if you need it. Going on with my convention however, and applying the birail tool in using my convention yields:
And with a little application of the Sculpt Geometry tool set to “relax”…
I think now is as good a time as any to bring up a few troubleshooting points that I came across while refining this method. First, when creating your curves, you can use the Open/Close Curve tool to make sure you have a closed loop, which is great for saving you the trouble of snapping CV’s manually. However, be sure to remember that in doing this, the curve still has a discontinuity where the beginning and end of curve meets. When you begin detaching curves into components for the birail tool, this may result in a ‘fifth’ curve you didn’t plan on having, and it may be small enough in the viewport to easily miss and derail your birail, so to speak. It’s easily fixed by using the “Attach Curve” tool re-merge that extra strand with the nearest larger curve and we’re back to four curves again, like we should. Also, turn two-sided lighting off on all your viewports. It’ll help keep you aware of the direction all your surface normals are aiming, and letting you reverse normals as necessary to keep everything consistent.
Also of note, remember to ‘flush’ your history often. Some curve modification tools demand a clean object history to function properly (while others won’t work unless History is “on”, so you can’t necessarily turn it off completely either).
In any case, we’re ready to merge these two surfaces, so assuming you’re already familiar with how to do that, we’ll proceed from that point. Let’s select a row of faces on the first shell we created, because it’s the larger of the two (in poly count) and delete it. All that remains for a more natural blending here is to use either the Bridge tool, or the Append Polygon tool. The former is quicker, but often glitchy compared with the latter, so take that as you will.
Okay. Not too bad, but we’re not seeing much in the way of form yet. Let’s do the top of the muzzle next. I was going to use a construction plane here as with the other two surfaces, but on reflection, Matt’s nose is far too much like a ski-jump to use such a flat modeling surface effectively, so let’s look into using a makeshift Nurbs surface to use as a canvas and follow the contours more closely. I can still use the construction plane, but only as a place to create the dummy Nurbs surface. Note, that I don’t have to do anything in creating this nurbs surface other than make sure the shape and size is accurate to my eye. I’m not thinking about matching polys at all here, because I don’t have to any more, not until after we’ve drawn curves on this nurbs surface at least. That in itself is liberating.
Now I’ll take that little ski-jump there, and make it our live object. Then move to the front view where I’ll draw on it, following the contours of the bridge of the nose as closely as possible, and then bring it back up the mid-line. We can’t close the loop yet, however, because drawing a curve on a Nurbs surface the way we’ve done here makes the curve part of the Nurbs object, and we want the curve to be its own object. To do this, we go back to the Edit Curves menu and select the first item on the list, the Duplicate Surface Curves tool. Now that we’ve got the curve we need, we can delete the Nurbs object and close the curve to make it a loop. Then we proceed as we ordinarily would, detaching, and using the birail tool.
And as before, combining objects, deleting the appropriate number of edge polys, and bridging between the shells.
I get the feeling that if I were to just make a single birail surface out of this loop, it might end up being to ‘soft’ and button like. I want to add more structure, so I think I’ll do it in two passes, breaking down the single loop into two loops. The tactic I’m going to employ in choosing the locations to break the loop is twofold. I’m going to align those points as closely as possible to the perceived “turning edge” of the model where front becomes side or top, and two, line them up with the nearest vertex on the existing model. I’ll continue to re-attach and detach curves as I deem necessary to continue to create birails that sufficiently fill in the gaps and provide structure. I’ve numbered the edges as I reconfigure them to accommodate each successive birail in the following images…
In the last image in that string, you can see I pulled out the Insert Edge tool to accommodate the large polys that developed along the bridge of the nose.
Here’s a comparison shot to see where we’re at compared to the drawings.
The profile view is pretty much spot-on, though we can still see that in the front view, in the transition area between muzzle and cheekbone, there is some divergence. How I fix that will be evident when I pick this up in next week’s entry, where I investigate using these methods with solid stand-in shapes and intersections.
As a bit of a post-script to this entry, I have to wonder if anyone has come across this method of model-building yet, with so much potential to avoid the agonizing prospect of hammering away at vertices or individually building edge loop after edge-loop through extrusion. It’s just not a very intuitive artistic process. One of my fairly regular habits is searching for techniques and methods others have found in how they approach certain problems, and see if I can adapt them for what I’m doing. But on this particular subject, what I have found out there rarely ventures away from only the most rudimentary techniques. If anyone has any further ideas for refining or combining this method with others they’ve seen, I welcome all comments to that end.