In this exercise, the setup is critical to getting a good result. Taking extra care in the preliminary steps will save you many headaches later on, in fact, it may make the difference between a successful and an unsuccessful model.
We’ll begin with an outline of our workflow, so we get a good conceptual understanding of what we’re doing step by step.
Load image planes into the front and side windows. Optionally, you can bring in image planes for the top and perspective views for additional reference.
Rough out the basic shape of the head using a default primitive sphere. Cut the sphere in half along the line of symmetry and delete one of the halves.
Decide on the surface parameterization you want for the final head. Project curves on the surface to represent the U and the V direction of the surface. Construct new surfaces from these curves.
Rebuild the new surfaces, align the isoparms to each other and attach them together for the new head surface.
Refine the shape of the new head using various deformation tools and Construction History.
Whether you use photographs or illustrations for your image planes, it’s a good idea to edit them in a program like Photoshop before bringing them into Maya. Make sure of the following:
The scale of the images should be the same. Make sure that key points on the head such as the top, the chin and the eyes line up from front to side.
Reduce the size of the image plane by converting it to a grayscale image and compressing it to a JPG format. Maya will read several image formats including TIFF, RGB, MayaIFF, GIF and others.
Select the camera to which you want to attach the image plane and create the image plane under the shape node tab, in the section labeled Environment
Use locators to mark the position of key points from front to side.
Use the centerX, centerY and centerZ values to place the image planes properly in your scene
Adjust the intensity of the image plane by changing the values of the Color Gain and Color Offset values in the Attribute editor. The Color Gain is a color value multiplier, the Color Offset is a value that is added to current values. Adjusted together, the background of the image plane can “disappear” into the values of the grid, and the image itself can be “ghosted” so it won’t interfere with the colors of your wireframes, CVs or other nodes in your scene.
The Display Mode will toggle the image plane display between Off, Outline, RGB, RGBA, Luminance or Alpha.
NOTE: You can make a button on the shelf to toggle your image planes on or off. Open up the script editor and clear the history and the input windows. Change the display mode of the image plane, and note the syntax of the command that is echoed in the history window.
Change the display mode to off; the command should read,
setAttr imagePlane1.displayMode 0;
The command setAttr means “set attribute”. “displayMode” is the attribute being set. “0” is off, “1” is Outline, “2” is RGB, and so forth.
Highlight the text that turns the image plane off, middle-click-drag the text onto the shelf, and you now have a button that turns the plane off. Repeat this procedure for turning the plane on, and for the on/off values of the second image plane.
You can change the default icons and put labels on them by clicking on Options->CustomizeUI->Shelves.
Sculpting the Primary Shape from a Sphere
The next step is to rough out the basic shape from a primitive sphere. You can bring in a sphere using the default settings, but since you’ll be adding isoparms later anyway it may be better to set the number of spans and sections to a higher number, such as 12.
Rough out the general size of the sphere by scaling, alternating between the front and side windows. You can further refine the shape using several methods.
Select individual CVs or groups of CVs and translate them to shape the sphere
Select hulls to manipulate rows of CVs in their entirety.
Once the shape has been roughed in, use Artisan to sculpt the bone structure of the face. Pull the chin, the cheeks and the brows, push the eye sockets in.
You’ll find that the geometry is not heavy enough in spots to get close to the shape you want. You can insert isoparms as needed to increase the geometry.
Right-click on the model, on an isoparm or at the intersection of two isoparms.
From the marking menu that appears, drag your mouse to “Isoparm”
Left-click on an isoparm that is oriented in the same direction as the one you want to insert. Drag the yellow indicator to the position you desire.
Shift-click on other isoparms to insert several at one time
From the modeling module, select Edit Surfaces->Insert Isoparm.
When using Artisan, the following settings may help you define your tool and refine your stroke
Under the “Sculpt” tab, experiment with the Max Displacement slider until your stroke has the effect you are comfortable with. The Opacity value is a multiplier for the Max Displacement, which usually means that each stroke will result in a fraction of the maximum.
Radius (U) will define the size of the brush if you are using a mouse. If you are using a tablet, the Radius(U) defines the upper limit of the radius, while Radius(L) defines the lower limit, based on stylus pressure.
Under the “Stroke” tab, setting the Reflection to “On” will duplicate your stroke across either the U or V direction, based on the first isoparm (this is why you oriented the sphere the way you did in the beginning)
If your brush becomes distorted while going over rough areas, you can “lock” the shape of the brush by setting the Stamp Compensation to Grid under the “Misc.” tab.
“Operations” (Push, Pull, Smooth, Erase) work in conjunction with the Sculpt Variables, and will function in whatever direction you have selected.
NOTE: While it is important to sculpt large bone structures with reasonable accuracy, the details such as the shape of the nose and the skin around the eyes can be left until later. Use the illustrations in this manual to get an idea of how detailed this initial sculpture needs to be.
As you sculpt, you will undoubtedly cross over the line of symmetry in V. To realign the sphere and regain bilateral symmetry, you can periodically perform the following operations:
Select the center isoparm in “U” and detach the sphere using Edit Surfaces->Detach. Delete half the sphere.
In the Front window, right click on the model and select Hulls from the marking menu. Select the hull on the very edge of the model.
Using the move tool and the Grid Snap tool (or holding down the “x” key), click on the red arrow and snap the hull to the Y-axis.
Select the model in Object mode, and duplicate it with a value of –1 on the X-axis. With both halves selected, use the Edit Surfaces->Stitch->Global Stitch tool. This will re-align the surfaces so they are tangent to each other.
Select the edge isoparms from one half, shift-select the edge isoparm from the other, and use Edit Surfaces->Attach->Blend to reattach the sphere.
Deriving the Final Geometry for the Head
Now that we have a fairly accurate head shape, we need to reproduce the shape with parameterization more suitable for the way we want to animate it. There are several ways to accomplish this, but we are going to focus on one that leaves the mouth geometry open, and radiates isoparms outward from the lips. This method concentrates the most geometry around the mouth and lips, giving us the most flexibility for accurate facial expressions and lip-synching.
Model with correct parameterization
Lock the model into the correct shape:
Divide the head in half along the line of symmetry, as described earlier.
Adjust the edge of the half-sphere by snapping the hull to the Y-axis
Duplicate the sphere with a value of –1 on the X-Axis
Select both halves, select Edit Surfaces->Stitch->Global Stitch. In the Global stitch options, select the following:
Set Stitch Corners to Closest Knot
Set Stitch Edges to Equal Params
Set Stitch Smoothness to Normals
Leave the remaining settings at their defaults. This will ensure an accurate stitch.
Once the surfaces are stitched, select Edit->Delete by Type->History on both halves
Delete the second half again.
Define the U and V parameterization of the new shape:
View the head in the front window and create the small curves encircling the mouth first. You can use primitive circles and scale them for these curves.
Select the curves and the surface, and click on Edit Surfaces->Project Curve On Surface->Active View. This will project curves not only at the mouth but at the back of the head as well.
Select the curves on surface, Edit->Delete By Type->History.
Select the original curves and the Surface Curves at the back of the head and delete them.
Switch to the side view and continue drawing curves as illustrated.
Begin with concentric curves around the mouth, duplicating, scaling and translating the curves as you work your way outward.
Slowly begin to fan these curves across the top of the head until they are nearly parallel descending down the neck.
NOTE: Creating quality curves here is very important. Take extra care to make sure the curves are smooth and evenly spaced. You need only as many curves as necessary to define the surface, you can always add more isoparms as needed later.
Once the curves are created, project these curves onto the surface in the same manner as before.
Select the curves and the surface
Edit Surfaces->Project Curve on Surface->Active View
Select the curves on surface, delete history
NOTE: If you are certain about the position and quality of the curves on surface, you can delete them at this point. However, if you think you may need to repeat this procedure, you can place the curves on its own layer and make the layer invisible. Make sure that you delete history before you do this.
Continue by drawing the curves representing the “U” isoparms for your surface
Here you are beginning to create separate surfaces to attach together to create the head. Building separate surfaces gives you a better chance of controlling the overall parameterization of the surface, resulting in higher quality and greater sculpting control.
As you draw the curves in the “U” direction, try to make each intersection as close to 90 degrees as possible.
The first curve you draw should intersect the mouth at the corner, the remaining curves should be spread evenly.
Project these curves onto the surface and delete history, the same way as before.
Place the projected curves on the same invisible layer as the others, or delete them.
Select all the curves on surface and duplicate them
In object mode, turn all options off, then right-click on the curves selection mask
Place a check next to Curves On Surface
Click-drag across the entire model to select the curves
Edit Curves->Duplicate Surface Curves
Delete history on the duplicated curves
Place the sculpted sphere on a separate layer and turn off the visibility on the layer.
NOTE: If you view the CVs on the duplicated curves, you’ll see that the parameterization is dense and uneven. This is not important at this time, as we will ultimately rebuild the surface.
Create four separate surfaces:
Select all the radiating curves, then shift-select one of the cross-curves
Switch your view to the side view
Edit
Curves->Cut Curve
In the Cut Curve options box, select Use Direction, Active View, Using Last Curve and Keep All Segments.
Repeat this process for the three remaining curve segments.
Select all the curve segments at the top in order, and loft them together. The resulting surface will be very dense. Delete the history and rebuild the surface.
In the Rebuild Surface Options, make sure that you use the following settings:
Rebuild Type to Uniform
Parameter Range to 0 to #Spans
Number of Spans U should be one less than the number of curves
Number of Spans V should be 3 or 4, to create an even distribution of isoparms. Make this decision on a per-surface basis – the surfaces don’t have to have the same number.
Repeat this procedure for the remaining segments
Prepare to attach the surfaces to create one continuous surface for half the head:
Select all rebuilt surfaces and delete history
Delete the construction curves, or place them on a separate layer and make the layer invisible
Select all surfaces again and Edit Surfaces ->Stitch->Global Stitch
Delete history
Attach the surfaces:
Right-click on the first surface and select Isoparm from the marking menu
Select an isoparm in the correct direction for the attach, and drag the yellow indicator to the edge of the surface at the site of the attach
Right-click on the second surface, select Isoparm again
Shift-select an isoparm and drag the indicator to the site
Edit Surfaces->Attach->Blend
Repeat this process for the remaining surfaces.
Select the surface you just created and delete history
In the front window, make sure that the edge of the surface is straight along the Y-axis. If not, snap the hull to the axis as you did earlier
Duplicate the surface with a value of –1 along the X-axis
Edit Surfaces-> Stitch-> Global Stitch
Delete history
Select the edge isoparms of the two halves as you did for the separate surfaces, and attach the two halves of head together.
Select the surface, Edit Surfaces->Open/Close Surface. In the options, select the “V” direction and the Blend option to close the surface.
You now have a single, uniform, closed surface for sculpting and animating a human head, with parameterization suitable for accurate and convincing facial expressions.