The Wind-up
Cow Tutorial
Introduction to computer animation
using Maya
Part 2: Texturing
The first thing you need to decide
when creating shaders is what "material" to use. We will discuss
all the possible materials in class, but for this cow toy we will most likely
want to use a Phong. The material determines what sort of surface the object
has (as in how it reacts to light). A Phong is a plasticy looking material.
To create a new shader open the multilister >Window>Rendering Editor>Multilister.
In the Multilister menu click on >Edit>Create. This opens the "Create
Render Node" window. It opens to the materials tab, where all of the
possible materials are listed. Click on the shader ball named "Phong".
Our first shaders will be simply
solid colors. To choose a color, double click on the shader Group sphere in
the Multilister, and the attribute editor for the Phong opens. Click on the
square of color (initially it will be gray) to open the color chooser. Select
you color on the color wheel or from the palette and click accept. For the
horns of the cow choose a yellow. Now the Phong in the Multilister is yellow.
To assign the shader to an object,
select the object (in this case, the horns) and in the Multilister menu
click >Edit>Assign. That is it. You can also Middle Mouse drag the shader
onto an oject in the view window. Now create orange, red, white and black
Phongs and assign them to the cow as in the scene below:
I used a dark gray Blinn shader
for the key. A Blin is used for a more metallic look. Don't texture the mouth,
arms, body or head just yet.
Creating Animatable Eyes
Now we will create an eye assembly which will allow
for animation of the direction the cow is looking as well as the ability to
blink. We want to build the eye assembly at the origin so we first need
to hide the rest of the cow Box-Select all of the Bee surfaces and press
"display> hide> hide selection" ( hot key- cntrl
h). Or place them in layers and hide the layers.
Create a nurbs sphere. (this time you can reset
the option box to use the defaults). In the channel box rename eyeball. Before
we create aim-constrain the eyeball to a locator, however we need the put a
texture on the eyeball surface so that we can tell which way it is looking.
The Eyeball Shader
To better see the texture as we work, select the
sphere, and hit hot key 3 (smooth display) and 6 (show textures).
Blinn is the shiniest material, a good choice for an eyeball so create a new
Blinn. A new Blinn shader ball appears in the multilister. With
this shader ball selected, click on your sphere, and in the multilister click
on assign. Your sphere should now look shiny although still gray.
Double click on this shader ball (or use hot key cntrl a) to open the attribute
box for the shader. In the box for ramp rename it eyeball". Under
"common material attributes" there is a line called color. You sill see
a color box (grey by default) with a slider, and a small checker box to the
right.
This little box is for mapping
the attribute. Click on this box. The "create render node" box opens
again. This time we want to create a "ramp" map for the color, so click
on "Ramp". The attibute box for the ramp now appears, and your sphere
should appear red, blue and green. Change the ramp attibutes as folows:
Type - U ramp
Interpolation - none
This changes the direction
of the ramp and makes the edges sharp. We only need two colors for the
eyeball. The ramp color box still shows red, blue and green. Each
color has a square box with an x inside on the right side. Click on the
x-box for the blue color to delete it. Each color also has a small circle
to the left. Click drag the red and green circles up or down to adjust
the placement of the colors.
NOTE: The eyeball at this point should be looking
straight up along the Y axis. This is correct for now - DO NOT rotate the sphere.
This is important for when we do the constraint.
The eyeball ramp attributes
Once you have the two colors properly placed, we
want to change them to black and white (or whatever color eyes you character
has) . Select the green color (click on little green circle) then click
on the green box next to "selected color". The "color chooser" box opens.
Select a black shade in the color chooser by clicking on it, then press Accept.
Change the red on the ramp to white the same way.
The Aim Constraint
Now we have an eyeball with a pupil, and we can
aim constrain it. Close the Attribute editor and the Multilister. Group the
eyeball to itself, creating a group node. Name this new node eye_group. Switch
to the "Animation" menu. Click on (create> Locator).
A green t appears at the origin, (which in this
case is inside your sphere). Move this locator along the X axis until
it is in front of the eyeball. Rename it eye_aim.
When you aim-constrain something you should no longer rotate it directly with
the rotate tool. Moving the locator will cause the eye to rotate. The aim-constraint
and the pupil texture ramp are actually aimed in different directions. That
is why we need to greate the extra node (eye_group). We can constrain
eye-group to the locator, and still be able to rotate the eyeball
because it is lower in the hierarchy. Now select
the eye_aim, then shift-select the eye_group (the order of selection
is important) and press (constrain> aim).
Now you can rotate eyeball so that the pupil is looking directly at the
eye_aim (locator). Now select only the eye_aim, and move it -
the eyeball should always look toward the locator. Try rotating the eye_group,
and you will see that it is constrained and can no longer be rotated with the
manipulator.
To review the steps:
1. Create Sphere (eyeball)
2. group eyeball to itself (eye_group)
3. create locator (eye_aim)
and place it in front of eyeball
4. select eye_aim, shift
select eye_group and >constrain>aim
5. rotate eyeball until
it is looking at eye_aim.
6. test my moving eye_aim
and the pupil should follow
*****
*NOTE Please
use a primitive sphere for your eyes, and for now DO NOT modify its shape. In
order for the eye to rotate properly it must remain a sphere. later you can
use a lattice deformer to change the eye shape. If you modify the shape
of the sphere this is what happens:
The eyeball modeled with a lattice
can rotate according to its original spherical shape maintining the modeled
shape witin the lattice. The eyeball modeled directly, with no lattice, rotates
according to its own center pivot, and thus in an oblong eye, such as the one
pictured above, when modeled with a lattice the pupil will seem to be moving
on the surface of the eyeball. When modeled without a lattice will pivot right
out of its socket. After we have modeled the eyelid and made the second eye
we will reshape them with a lattice.
*****
To add an eyelid
create another sphere and make is slightly larger than the eyeball. (If
your eyeball scale is 1 try 1.02 for the eyelid) Manipulate the lower
hulls to form a half sphere with a lip fot form the eyelid. Name the new sphere
eyelid, and assign it a plain white Phong shader.
Now we want
to duplicate this set-up for the other eye. Shift-select eye_group, eyelid
and eye_aim, and position them on the characters left side, then press (edit>
group) (*Note do the selecting in the outliner
or hypergraph rather than box-selecting in the panel view, and be sure you pick
eye_group not eyeball to maintain the grouping you did earlier) (Hot key
cntrl g). Name this new group eyeset.
Move the eyeset into place. Now press (edit>
duplicate> option box). In the duplicate
option box click on "duplicate upstream graph". This ensures that all
connections (such as the aim constraint) are included in the duplicate. (*NOTE:
Due to an apparent bug in Maya your new eyeball may have a funky looking color
or texture - simply reassign the shader and it willbe OK.
New eyeset
with funky shader
We now have
eyeset2. You can rename each item in a hierarchy with a prefix. select eyeset
and >modify>prefix hierarchy names and type
L_ in the box. Now each node in L_eyeset has an L_ infront of it. Select eyeset2,
and prefix R_. Then scale R_eyeset2 to -1 in X to place it on the right side
of the head. We can now control the eyes independently, however we will certainly
want to control both eyes with a single control. to do this shift select
the two locators (L_eye_aim and R_eye_aim) and group them. Rename this
group Eye_Control. Since this is a new group the pivot point is at the origin,
we want it to be at the center of the group (that is between the 2 locators)
Select the Eye_control group and >modify>center
pivot .
We now have a single node
for both eye_aims to control the eyes , however there is nothing to see in the
view panels to represent this node. We can choose it in the hypergraph
or outliner but it is much handier to use a visual handle in the view panels
when animating. Everything in Maya is actually born with such a handle
- it is just invisible by default. In order to make the Eye_Control handle
visible, select it, and press (display> object
component> selection handle).
A very small t icon appears at the pivot center of the group, this is the selection
handle. Choosing this handle chooses the Eye_Control node. If you
plan on only controlling the eyes as a team (which is typical unless you want
your bee to cross his eyes) you can hide the locators (select L_eye_aim and
R_eye_aim) by pressing (display> hide> hide selection).
eye control handle
Up to this point the eyeballs have been perfect
spheres. We needed to keep the spherical shape in order for the rotation of
the eyeball to work with aim constraint. We can now modify the shape with a
lattice to fit the cow. Switch to the Aimation menu set, select the groups which
represent the eye geometry (do not include the eye controls or aims) and click
>deform>create lattice. A wire box appears around the eyes. This is the
lattice. Switch to component mode (F8) and be sure the selection mask for lattice
points is on. (it is the same mask as for CVs). In the channel box you can increase
the divisions of the lattice - I used 5 T divisions, 5 U divisions and 2 U divisions.
Now you can manipulate the lattice points much the same as you would CVs, to
make the eyeballs and eyelids the proper shape without interfering with the
aim constraint. Notice also that if you rotate the eyelid it conforms to the
shape of the eye as it blinks.
eyeballs and eyelids modeled with
lattices
IPR Test Rendering:
Although you can see the
shaders somewhat in the viewports, it is a good idea to test render as you add
textures to see what you really have accomplished. To set up for the IPR
(Interactive - Photographic - Rendering) maximize the perspective window and
tumble and dolly in to get a good view of the surfaces. Since these renders
are just tests we will reduce the quality in order to speed things up.
Open Render Globals - (window>
render globals), and under the "Common"
tab, change the folowing attributes:
Resolution: Render resolution:
320 x 240 (this is about half size so the rendering will be quicker)
Anti-Aliasing Quality: medium quality
Set up the perspective window
to get a good view of the surface and press (Render> IPR Render into new window).
Click drag a select box aroung the area you may adjust in the render window
to identify the region for the render to update. Now as you make texture
changes - such as color, transparency etc. they are quickly updated in the render
window. DO NOT CHANGE THE VIEW IN THE PERSPECTIVE WINDOW. .
When you are satisfied, close the render window.
Texturing the rest of the surfaces
(Once again, I'd like to remind
you that this tutorial covers just the basics. You may embellish your
model textures to your heart's desire. In class I will be showing you
more information about texturing such as bump and displacement maps, as well
as how to animate textures.)
Open the multilister (*note: texturing can
also be done in the hypershader but for this excercise we will use the multilister).
Be sure that all you surfaces are in smooth display mode (3)
and that all views indicate show hardware textures (6).
Since the arms
and hooves are a single surface we can use a ramp to make them two colors.
Create a Phong shader and assign it to the arms. In the shader attribute
box click on the map for color (just like we did for the eyeballs), and select
"ramp". Change type to U ramp and interpolation to none. Now just
like the eyeball shader, delete a color, and change the remaining color to black
and white. Move the black and white up or down until, in your perspective window,
the arm is white and the hoof black.
You can assign this
same shader to the other arm.You can also use a Ramp texture for the mouth,
making the inside red and the outside orange.
The cow so far:
Painting Textures:
You can actually paint in 3 dimensions
in Maya. We will paint the spots onto the cow's head and body. To paint the
body go to the Rendering menu set. Select the cow's body and click >Texturing>3D
Paint Tool and open the option box. To begin with if you hold your mouse over
the surface a large red circle with an X appears. The surface is not yet paintable.
The first step is to assign a texture. Scroll down in the 3D paint window to
the button "Assign File Texture" and click it. A box opens asking
what resolution you want to use for the resulting image file (512 x 512 should
be fine) Maya now knows to create an image file of whatever you paint to be
used as the color in your shader. (It is a good idea to use a .jpg or .tif
format for the file so that you can later open it in Photoshop or other image
editing software to modify or refine it.) Now when you hold the mouse over
the body of the cow a large red circle appears without the X. This is the outline
of your paintbrush, indicating that the texture has been assigned and surface
is paintable.
.
Paintable cow
Scroll back up to the top of the 3D
paint window and, under the category "Flood", change the flood color
to white and click "Flood Paint". This makes the entire cow body white,
and we can paint on black spots. In the category "color" change the
paint color to black. Obviously the size of the paint brush is too big. To make
it smaller, either change the slider in the box marked radius, or you can change
it interactively in the view window. You do this by holding down the "b"
key and Middle mouse dragging in the view window. With a smaller brush you can
begin to paint on the spots. (Note: labeled Artisan there are several brush
profiles to choose - you want the one wth hard edges).
When you are happy with the spots
scroll back dow in the 3D paint window and click "Save Textures".
That is it - Now create a shader the same way for the cow's head and she is
done.
Final Textured Cow
