The Wind-up Cow Tutorial

Introduction to computer animation using Maya


 

Part 1. Modeling the basic object:

Remember: this project is very basic.  You may embelish your model as much as you want.  It need only be a bi-ped (two legged) creature with some moveable parts since  I want to use several modeling and animation methods on this object .   So, within those guidelines feel free to go wild.

***Before beginning -create a new Project using the default folders***

(>file >project >new project click "use defaults" click accept Be sure you create you project in your home directory which should be the Z drive)

The Head:

(Be sure you are in the modelling menu)  In the front view window - begin with a primitive sphere (create> nurbs primitive> sphere - optionbox ).
In the option box specify 8 sections and 8 spans.   Use a radius of 0.7 to make the object at the scale I am using for this tutorial. Press "Create".  The sphere is made up of hulls and CV’s which we will manipulate to form the ears.

-press "F8" to switch to "component editing mode" or click on the icon idicated below.   Choose the selection mask which allows you to select only CV’s ( a black square). 

With the translate tool (hotkey w) , in the front view window, select a CV on either side, then shift select the CV on the other side of the sphere. Scale them out along the X axis, and translate them up along the Y axis to form two ears.

manipulate CVs to form ears

Next, choose the selection mask for NURBS Hulls. (If you don't know which icon is which on the status line hold your mouse over the icon and the components that icon makes selectable appear as a list.) Select the Hull just below the ears and scale it down proportionally (that is along all three axes), by using the center of the manipulator.

In the side view flatten the sphere a little bit by returning to "Object mode" (F8) and scaling down along the Z axis. Continue to manipulate either CVs, hulls or at the object level until the head resembles this image:

In the Channel Box name this object "head"

*Note: You can " walk-select" Hulls and CV’s with the Arrow Keys.

The same method can be used to form a muzzle for the cow.   By manipulating the Hulls and CV''s for something that is roughly a flattened sphere . Press F8 again to toggle back into "object editing mode" and, with the move tool, select the muzzle to place it below the head. Make an indentation at the bottom in the front to make room for the mouth. Name this object "Muzzle". Don't worry that the two objects intersect.

The horns can be created from a primitive cylinder. Press >create >Nurbs Primitive>cylinder and open the option box. Create a cylinder along the Y axis with 6 sections, 3 spans and a radius of 0.15. Be sure to indicate that you do not want "caps" on your cyylinder.

Setting up some attributes of your primitive before creating can save time, but you can always modify it afterwards.)

In "object-editing mode" move the cylinder to the approximate location of the left horn. Scale the cylinder to form an horn-shape.   Press F8 to toggle back to "component editing mode" and select the top Hull on the horn. Scale the Hull down until all the CV’s seem to occupy the same space, like pulling shut a drawstring.

(*Optional: To be sure the CV are all truly at the same location there is a trick. Go to the "Animation" menu, select the hull and press >deform>create cluster. A "c" appears at the Hull location. The cluster is a representation of all of the CVs of that hull. Now scale the Cluster to 0 in X,Y and Z in the chanel box. Now the hole in the cylinder is absolutely closed. Before continuing however you must get rid of construction history. Select the cylinder, press >edit>delete by type>history)


scaling down a Hull to close end of cylinder

To make the other horn we want to mirror this one. In Maya to create a mirror copy you use the (edit> duplicate - option box) command, however, in order for this to work properly the pivot-point of the object to be mirrored must be at coordinates; 0,0,0. That is the center of the grid. Well, our cylinder's pivot point is  at the center of the cylinder right now..  However, if you group it to itself (this will create a new node for the cylinder in the outliner, above the original node in the hierarchy) the "group" node by default will have it’s center at 0,0,0.  To do this,  in "object editing mode" select the cylinder. Press (edit>group).  Now notice, in the channel box this node is called "group1". Rename this L_horn. With L_horn still selected press (edit> duplicate - option box).   In this option box there are 3 fields next to scale – they are from left to right x,  y and z. To make a mirror duplicate type 1 in the first (x) field. This creates an object with identical y and z information as the first, but the x value is negative. This is a mathematical description of a "mirror" object. Press "duplicate": you should now have a right horn.  It will be called L_horn1,  but you should rename it R_horn.


duplicate option box set to mirror object across X axis

*NOTE  When you have created an object as a mirror image you will notice in the channel box that the X scale attribute says -1.  Once you are happy with the object it is a good idea to press (Modify> Freeze Transformation) .  This will get rid of the negative scaling, without changing the surface, which can avoid problems with grouping later.

Model a mouth from a primitive sphere. Manipulate the object, CVs and hulls until you have something like the image below, name it Mouth, and and place under the muzzle.

This completes the Cow's Head for the moment. We will get to his features a bit later.

NOTE: Do not model the eyes of you character just yet. We will be getting to that in the texturing section because the eyes need to be created in a particular way to make them animatable.

 

The Body:

The body of the cow is also made from a primitive sphere. Be sure to flatten the top and bottom of the sphere by placing the hulls close together. Create one arm from either a sphere or a cylinder, and make a mirror duplicate to form the other arm. Place the body slightly below the head - allow enough room for the head to tilt from side to side when we animate it.

The is how your cow should look at this point

:


The Neck of the toy looks at first like a simple cube. However it has somewhat rounded corners. We can achieve this very easily with the "round" tool. First, create a cube, and scale and translate it so that it it forms a neck tucked into both the body and head. Once it is in place you will want to hide the body & head of the cow to work on rounding the cube.

The easiest was to do this is to use layers. (Make sure that >display>user interface>channelbox/layer editor is turned on.) Create two new layers by clicking >layers>create layer (twice). If you double click on these new layers you can name them and assign the objects in them to a color. Name the layers, Head, and Body. Group all of the head parts into a single node, and do the same for the body. Select the head node, and highlight the Head layer, and click .layer>assign selected objects to current layer. Now that the head is in a layer, you can make it visible or invisible, template it (grayed out wireframe - unselectable) or reference (shaded but unselectable) by clicking in the boxes next to the layer. the first box toggles between "V" visible or empty, invisible. In the next box one click is T for template, another click is R for Reference, and a third click is back to normal.

 

In Maya a primitive cube consists of 6 separate planes. They each have a node in the outliner. Using either the outliner or the view window in shaded mode, delete the top and bottom of the cube. (make sure you returned to the modeling menu after creating the clusters earlier). Next click on >edit Nurbs>Round tool. Once the tool is selected, drag a"box select" across the line where two sides of the cube meet. A radius icon sould appear. Select each of the other edges of the cube. You should now have a radius icon at each edge like this:

Adjust the radius of each side by either typing a new number in the channel box, or interactively by dragging the radius icon in the view window. A radius of .1 should do fine here. Then Enter. In the outliner Group the "rounded surfaces" together, delete construction history (>edit>delete by type>history), and delete the original cube.

 

 

Additional Features:

Now let's go back and add some features. The nostrils are indented on the surface of the muzzle. We need to cut a couple of nose holes in the muzzle and fill it in with a concave surface. One easy way to do this is by intesecting a small sphere with the muzzle and trimming away part of the muzzle and part of the sphere. Create a small Nurbs sphere and place it so that it intersects the muzzle where you want a nostril. Make a mirror duplicate of this sphere now for the other nostril

Shift select the nostril sphere, and the muzzle and click >edit Nurbs>intersect surfaces>option box. Be sure that you check the box which says you want curves on both surfaces. This creates a "curve-on-surface" at the intersection of the two surfaces. now when we "trim" the surfaces Maya will essentially remove the portion of the surface on one side or the other of the "curve-on-surfaces". To trim select the nostril sphere, and click >edit nurbs>trim tool. The sphere is now show in white with the surface divided by the curve at the intersection. Click on the area of the surface you want to keep, in this case the part of the sphere inside the muzzle and hit enter. Repeat the process for the second nostril sphere.

One way to make the edge of the nostril less sharp is to extrude a small circle around the trimmed hole. Create a Nurbs circle and scale it down to .01 in all dimensions. Do not move it from the origin. Select the muzzle, hit F8 for component mode and select mask the icon for Isoparms (which includes "trim edges"), and select the edge of the nostril hole. If the entire edge is highlighted in yellow you may proceed to the next step*: Select the circle, then shift select the trim edge, and extrude >surfaces>extrude using the following:

Style: tube
Result Position: At Path
Pivot: Component
Orientation: Path Direction

 

*If when you select the trim edge only a portion is highlighted in yellow you need to select the edge in parts, as it is not one continuous curve. Select each part and click >edit curves>duplicate surface curves. You now have several CV curves at the edge. Select each curvespart and click >edit curves>attach curves. (Make sure keep original is off and you have it set to "connect" not blend in the attach option box). When you have one curve, delete construction history. Now you can select the circle, and shift select the curve and extrude as above.

We can create a curve-on-surface another way to make the tail of the cow. Select the body surface and click >modify>make live. The surface of the body is shown in green wireframe. The surface is now "live". That means you can draw curves directly onto the surface. In fact if you try to draw a curve anywhere else you can't. Every CV is snapped onto the live surface. For the tail draw a squiggly curve onto the rear end of the cow. Now click on the body and hit >modify >make not live to return the surface to normal. You can now extrude a tail by creating another circle at the origin (I scaled mine to .03 in all dimensions), and extruding it along the tail curve just like we did for the nose edge. Modify the two ends of the extuded tail to close them up and add a little sphere at the tip amd model it into a point

.

The Legs:

All we have left to model (aside from the eyes) are the legs. The bottom surface of the body of the cow has two slots for the legs. We can slice away part of the body at the bottom and replace it with a planar surface to make the slots more easily. Somply select an isoparm at the bottom ege of the body and click >edit nurbs>detach surfaces. the body is split into two surfaces, and you can select and delete the flat bottom. Now select the same isoparm and click >surface>planar to create a planar surface.

*NOTE:

For a planar surface to be successful, all of the CVs of the curve must be on the same plane (co-planar). Since the isoparm I chose was part of the primitive sphere and all the CVs were still on the same plane (that is all the Y translate values were identical) my planar surface worked. If your isoparm is not quite co-planar, after you detach the surface choose the last hull and snap it to the grid (hold down the X key to snap to grid) using ONLY the Y translate arrow so that all the CVs are at the same Y value, then move it back into place.

Legs:

The legs of the windup cow fit into two slots on the base of the body. We can trim out those slots like we did the nostrils. In order to trim the surface you must create Curves-on-surface. This time we are going to create a curve and project it onto the planar surface at the base of the cow. Before creating your curves it is a good idea to hide all but he body of the cow. In the top view create a NURBS primitive square and place it on one side where you want the leg slot to be. Then make a mirror copy of the curve for the other slot. Still in the Top view - project the curves onto the surface by first selecting a curve, shift selecting the surface and clicking >edit NURBS>project curve on surface. When both slot curves have been selected trim the surface >edit NURBS>Trim Tool, and placing on the planar surface. As with the nostrils, the surface is divided into sections indicated byt white lines. Select the area you want to keep and Enter.

To finish off the edge of the slot, we want to create a lofted surface around the holes. First move the original curves you created to project onto the base inside the body to a position just inside the leg slots. Lofting creates a surface between two curves. We want to create surface between the trimmed edge of the slot and the original curve. To do this you must shift select one edge of the leg slot and the corresponding edge of the original NURBS square. (NOTE the NURBS square os selected in object mode whereas the trim edge can only be selected in componenet mode). Once you have two curves selected, click >Surfaces>loft. Repeat this project for all 8 sides of the leg slots

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Now for the actual legs. I simply duplicated the neck object we made earlier by rounding the edges of the cube, and rescaled it and moved it into place, then made a mirror duplicate. (No need to repeat work you have already done).


Feet:

One of the wind-up toy's feet consists of two parts, the platform and the actual foot (hoof?). To make the hoof I took a cylinder, and, like we did for the horns, I closed up either end by scaling down the Hulls. I positioned and scaled the cylinder. Now we need to remove the bottom half of the cylinder to make the feet flat. We could have created a 180 degree cylinder to begin with however it is easier to get a nice rounded end if the cylinder is 360 degrees. You can detach a surface at an isoparm. Every NURBS surface has a seam. If you look closely at the isoparms of the cylinder you will notice on isoparm is thicker than the rest. That is because it is actually two isoparms together, the first and the last of the surface and thus the seam. That means our Nurbs cylinder is already spearated at that isoparm, so select the corresponding isoparm and click >edit NURBS>detach surfaces. The cylinder is now split into two surface and we can simply delete the bottom half.

Teh cows hooves are not complete semicircles, however so we need to slice away some of the cylinder. Simply draw a straight curve in the front view, and project it onto to hoof, and do a trim.

Once again we want to finish off an edge. I decided to create and interior of the hoof by offsetting the surface and then lofting between the two edges. To create the offset surface, select the hoof, and click >edit NURBS>offset surface and open the option box. I used an offset distance of -.05. (you may need to experiment a bit). This creates the interior of the hoof. Now we can shift select the trim edges and created a loft.


 

When the hoof is complete, delecte construction history, (>edit>delete by type>history), group all of the parts together, and name the node Hoof. Then make a mirror copy for the other hoof.

All that is left is the platform for the hooves. The platform is a roughly "C" shaped object. First draw the curve (Hide everything but the hooves for the moment). In the top view draw a curve like the one below. Using this curve create a planar surface (>surfaces>planar). Place the planar surface under the hoof. This is the top of the platform. To make the bottom of the platform simply duplicate the top and move it down.

Teh final step is to create a rounded surface between the two platform pieces. We are going to use a tool called the birail. The birail tool concicsts of a profile curve and two rail curves. the profile curve is sent along the rails creating a surface. Our rails will be the edges of the platform planar surfaces. We need to create a profile curve. For a birail to be successful the profile curve must be connected to the rail curves. The easiest way to do this is with an Edit Point curve since we only need t draw two CVs for an EP curve. We want to snap the new CVs to the existing edge curves.(make sure your EP curve tool option box specifies a cubic not a linear curve) In the Front View, holding down the "c" key (hotkey for snap to curve) snap one CV to the top platform edge and one to the bottom. Though we drew only two CVs a cubic EP curve still have four CVs in reality. In component mode you can move the two center CV to create a rounded curve.

Now for the birail: with nothing selected, >surfaces>birail >birail 1 tool. *Note: be sure to have the the help line displayed (>display>UI elements>help line) Now click first on the profile curve, then on a rail curve (a platform planar surface edges) which should highliht in yellow. Now click on the second rail (the other platform edge) and a birail should be created.


 

Once again delete construciotn history, group the platform pieces together, and make a mirror copy for the other foot. You will notice that the left and right platforms intersect each other. That is OK, when the cow walks her feet step over one another.

All that is left is the wind up key. I think you know enought now to try this on your own. They key I made consists of several cylinders, to form the post. Then I drew an outline of the key and made a planar surface (like the platforms) and created a NURBS circle, duplicated it and projected them onto the planar to trim out the holes. That created the front surface of the key, I duplicate and translated that surface to form the back. I then lofted between the trim edges of the holes and the planar edges to finish it off

 

Now all that is left is to group and name your cow parts. Be sure you have deleted all construction history. You can also delete any and all curves. All that should be left are NURBS surfaces. You cow will get eyeballs and well as textures in the next section.

  Completed Cow model

Go to Part 2.Texturing