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CAP 201a - Computer Animation I
Lesson 8 - Chapter 11, Textures and UV Workflow
Objectives:
Chapter 11 introduces more features of the
Material Editor, among them the Slate Material Editor mode. Objectives
important to this lesson:
- UV Unwrap
- Slate Material Editor mode
- Seams
- Bump map and specular map
Concepts:
A model that has a complex shape will often
require you to create a custom map that will fit only
that model. We approached this idea when we custom fit an existing
map to the Red Rocket's fin in chapter 10. In this chapter, we will see
that the process can be much more customized.
Project Exercise 1: UV Unwrapping
This exercise starts on page 226. Before you
begin it, set your project folder as directed and
open the supplied file named on that page. Upon
inspecting the file, you may note that the authors have added knee pads
and elbow pads to the soldier model, as well as straps supporting them,
another pouch near the holster, and perhaps more that I am not noticing
at this moment. A reason to go with their version this time, is that
the directions for the next steps depend greatly on the model itself.
You may be able to extend the lessons to your own model after working
with theirs.
In this chapter, save often. If you make an error
that is too far back to undo, your only choice is to reload a saved
file.
- The exercise starts by telling you to turn on Smooth+Highlights+Edged
Faces by pressing F4. (F4 only affects Edged
Faces.) This was already turned on when I opened the
scene, but the instruction should remind you that F4 is a toggle
button. If it turns off the feature you want, just press it again.
The text also tells us to turn on the Realistic mode
if we are running the Nitrous driver. This enables a shadow
enhanced model, which is different from Shaded mode.
 Select the model, open the Modify
panel, and add an Unwrap UVW modifier to the stack.- Click the plus sign for the Unwrap UVW modifier
to open its subobject list. Select Face
subobject mode. (As shown in the image on the right.)
- The text directs you to make a change on the Configure
rollout of the Modify panel, You will not see that
rollout at first, because it is the last rollout at
the bottom of the panel. Drag the panel up until the
Configure rollout appears. Do not click any unwanted
button while dragging the panel.
Turn off the check box for Map Seams.
Note, as the text says, that this will turn off the green highlight
that was on your model.
 The text tells you where
to look for the next button, but it is wrong. If you have dragged
the current modify panel to find the Configure rollout, you should look
next for the Peel rollout, which will be near the top
of the current layout. (Dragging panels is probably why someone
invented the Graphite ribbon.)
On the Peel rollout, find the Point to Point
Seams icon and click it. The icon art may
make it hard to tell that I am holding my mouse pointer over the second
icon in the Seams group in the image on the right. - To understand what you are about to do, consider the shirt
or top you probably have on right now. (If necessary,
politely look at someone else. No, lady, I'm an artist, not a
pervert.)
On most garments, there is a seam that starts under
the arm and runs up in front to the top of the shoulder
and down the back of the shoulder to where it
started. Another seam starts in the same place, but
runs along the under side of the arm toward the wrist.
You are going to use this tool to make seams just like that in the
model. You want the seams to run along the edges of existing polygons.
Remember, you are not cutting edges in the garment on the model, you
are establishing seams in the surface of the model. Seams are logical
places to unwrap the skin of the model, so a version of the skin can be
painted in Photoshop or some other art program.
Look at the illustration on page 227. Click at a vertex
like the one shown in the picture on the left on that page and continue
clicking on vertices in a line up
to the top of the shoulder. A blue line should form,
showing edges where you are cutting a seam
to unwrap the model. (You will not not see the dashed
line that the text says will appear if you drag, only
if you click a series of points.)
- Orbit the model, and continue clicking
from your last vertex to the next to complete a half loop
from the armpit to the top of the shoulder.
- Continue orbiting and clicking
to extend your seam back around to the point where you started.
- Orbit to a position where you can see the under
side of the model's left arm. Turn on the Point to Point tool,
if it is off. Click from the seam you cut, along
visible edges, to the end of the wrist.
Right-click to stop drawing the new seam.
The instructions are little light here, but there is one more
point to click
The seam has to run to the center point of the cap of the wrist. You
can't see that vertex because the hand is in the way. Time for
something new: wireframe.
Change to wireframe view of the scene. Get your
bearings, and figure out where you are. Orbit and pan
as needed to see both the current end of your blue
seam at the edge of the wrist, and the center point of the
wrist cap. Click your last vertex on the
blue line, and connect it to the wrist cap center.
Then, right-click to stop making the seam. In the
image above, I just did that. Turn off wireframe view
to keep your sanity.
- In step 10, you are told to repeat the
seams, this time on the model's right arm. Do that,
so you have similar seams on each arm, including the line to the wrist
cap center.
- Refer to the second picture on
page 229, but ignore the yellow edges. Look also at the blue
line in the second picture on page
230. (Magnifying glass time, again.)
Starting on the model's left side, extend the under arm seam down the
side of the model to the top of the pouch. However, note that you are
to outline the Kevlar cutouts using their inner
edges. This will not help much if there is no connection to the
existing seam, so connect it like the image below.
Once again, I am in wireframe view to see as many edges and vertices as
possible.
Continue the seam around the belt line closest to the
body. Run the seam above the pouches and holster, not
through them.
- Cut seams on each of the gloves
as directed in the text. Note that the gloves end inside
the wrists in this model, so you will have to use the
wireframe view to see the first and last vertices for the seam on each
hand.
 Finally, the text returns to the Material
Editor. Open it, and switch to the Slate
Material Editor.
The text directs you to look on the left panel
(Material/Map Browser) to find something. The first rollout
is called Materials. In it, the next rollout
is called Standard. In that rollout, find the Material
template called Standard. You can
double-click it, as the text says, or you can drag it into the middle (Active
View) panel. (Called View1 at this point.) The text
tells us that what opens is a Standard Material node.
The node (shown on the right) has a set of round connectors (sockets)
on its left side for input from
other nodes, such as map files. It also has a socket on its right
side for output to other nodes. Using these sockets
to connect to other maps and materials, nodes can be highly modified.- The text tells us to double-click the
input socket for Diffuse Color. When you do, a new
window opens. The text says the Material/Map Browser opens again, but
there is a difference. The new one does not have a
rollout for Materials: it expects that you want a map. Under Standard
maps, select the Checker map and click OK.
(This is a map supplied with the program that resembles a black and
white checkerboard.)
- You can pan and zoom in
the Active View panel to see that two
new nodes just attached to our Standard Material node. Each has a title
bar. The text says to double-click the title bar for
the Checker map. This opens a parameters
panel for it on the right side of the Material Editor. The first
rollout on that panel matches the picture on page 233.
Follow the instructions in the text to change the Tiling
values for the map from 1 by 1 to 5 by 5.
- Drag from the output socket of the
Standard Material and drop on the model. You will not
see the material in the workspace yet.
- As you had to do in the Compact mode, to see
a material in viewports, you must click the button on the Material
Editor's toolbar called Show Shaded Material in Viewport.
Why does it say shaded? In this sense, a shaded material is any
material that is not just a basic color. Connecting a map to a socket
for your material made it a shaded material.
- Save your file with a new name, and don't
get depressed by the way the model looks right now. The material is not
mapping correctly yet. We will address that on the arms in the next
exercise.
Project Exercise 2: Pelting the Left (and
Right) Arm UVs
Continue with your model from the last
exercise. The text tells you at this time that the reference image
objects are hidden in the scene, but you can unhide them if you want.
It gives no reason to have a preference, so leave them alone
for now.
The images in the sequence below are from working with the model's right
arm. You will have to do both arms, one at a time. You can start with
either one, but the text starts with the model's left arm.
- Select the model. Go to the Modify
panel, and select Face subobject mode from the
choices under Unwrap UVW in the modifier stack. Make sure Point to
Point Seam is turned off. Click one
face on the left forearm of the model as instructed. Click
the Expand Face Selection to Seams icon, which is the
icon on the end in the same line as Point to Point Seam. The faces on
the arm should all turn red, like the picture at the
top of page 234.
 Step 2 says that we need to unfold
the the UVs to create a usable pattern or skin. The word the program
uses is pelt. The text says to click the Pelt
Map icon in the Peel rollout to do this. Do
it, and have patience. You are only getting started. The horrible sight
in front of you will improve in a few steps.
- Two dialog boxes will open, like the ones
shown at the bottom of page 234.
The Edit UVWs dialog box is the bigger
one. On it, open the View menu, and look for
Show Grid and Show Map. Make sure both are
turned off. This will simplify your view a bit.
 On the Pelt
Map dialog box, find the Start Pelt button,
which should be on the top left corner of the box.
Click it, and wait for a
few seconds. If your processor is slow, it will not complete the job
instantly. When the pixels stop moving, click the
same button which now says Stop Pelt. My pelt for the
right arm at this stage is shown in the image on the right.
- The squares in the checkerboard don't fit yet. Find
and click the Settings box next to
the Start Relax button. Open the drop down box in the
next dialog box, and select Relax by Face Angles.
 You can click Start Relax
in either the box that just opened or the last one. Again, wait
for it to finish. When it is done, close the Relax
Tool dialog box.- Click the Commit button at the bottom of
the Pelt Map dialog box. This saves the change to the model in memory.
(It does not save your scene file.)
Close the Edit UVWs dialog box. There should
now be a recognizable checkerboard pattern on the arm you pelted.
- Save incrementally.
- If you just did the left arm, repeat
the entire process with the right arm. Save incrementally
again when done.
Compare the unpelted image to the final
image and you should see that the final version will
be much easier to paint.
Project Exercise 3: Unwrapping and Using
Pelt for the Head
The next exercise works on the head, onto
which you merged goggles, mask, and helmet in your model. As we will
see, the authors have merged another object, a helmet strap with one
piece on either side of the helmet.
- Note that the text tells you to save before you do anything
in this exercise. Not that anything might go wrong, but... I have a bad feeling
about this.
Select the soldier. Go to the Modifier
stack. Open the Editable Poly object, and select the Element
subobject.
Before you can make that last selection, the program should give you
the warning screen shown on page 237. When you see
this warning, and you will see it again, think hard before
going on. In this case, the text tells us this is a safe operation. You
are going to select the object lower in the modifier
stack (causing the warning) in order to select
an Element subobject. Your intent is to select
a piece of the model, but not to modify it at that
lower level. Modifying at lower levels in the stack
can cause unpredictable results.
- Choose Element subobject level, then
select the helmet. With the helmet
selected, go to the Graphite ribbon, find the Visibility
tab, and click Hide Unselected. Everything else
on the screen will disappear.
- Return to the Editable Poly level
by selecting it, then select the Face
level in the Unwrap UVW object. You are now back to a facet
of the top level object in the stack. This avoids
making a change in the lower level object.
On the Peel rollout, select Point to Point
Seam again.
Refer to the picture on page 237,
and make a seam on the helmet to match the yellow
line in the picture.
- Trust me: save again now,
if the helmet went well.
Proceed with the instructions here to put seams on
the goggles. Do the seam on the front
of the goggle between the goggle frame and the glass
first: it is easier. When complete, save incrementally
again. As you do the seam that is displayed in the lowest
of the three images on page 238, you will learn that
you cannot cut a seam from the inside
of a model element, only from the outside, which
means you will have to orbit the model from cut to
cut, maintaining contact with the outside
edges of the model. Another way to think of this is that you cannot
cut a seam unless you are on the Normal
side of a polygon.
 An interesting
challenge to cutting the seams on the goggles is that you will continue
to see the seams of the arms, hands,
torso, and helmet as you
do so. The helmet seam may be confusing,
so make sure each edge you cut is one you actually want
to cut. The good news is that every time you switch to another
subobject, you can see the seams you cut for the last one. If you are
merely missing some seam edges, you can go back to that subobject and
cut the seams, now that you know where they are. (Draw a picture first?
Take a picture? Don't lose your way.)
A question that I anticipate coming up at this time is "Do I
have to cut every edge in a strip of edges? Can't I skip ahead and cut
every other edge, or every third edge, and let the software fill it in?
It seems to do that."
You could try that, but it is a bad idea in an environment
where some of the edges and vertices are not visible. Eventually you
will miss an edge, connect a vertex to the wrong
place, go beyond the level of undo steps, and have no
way to correct your error but to go back to your last
save and start over from there. Been there,
done that. Don't go there. You will look for ways to expand your
profanity vocabulary at a moment like that.
- If you finished the goggles, save again.
Begin the task of seaming the mask by looking at the two rather small
images at the top of page 239. You will do better to
look at what the authors did.
You just saved, right? It is safe to open one of the authors' later
files to look at the seams in it. Don't
change anything in their file, just look at the seams
for the mask until you understand what they want, then come back to
your incrementally saved file.
I got the mask to work, played with the head until it worked,
then went for the helmet straps. Then the model got very uncooperative.
In the interest of time and sanity, browse through several pages with
me before we hurl the book at the wall.
- Beginning on page 240, the text asks you
to seam the rest of the body
according to tiny diagrams on page 241. Let's assume
it would have been possible if we were given decent instructions and
illustrations.
- Page 242 begins pelting the parts that
have not been pelted yet. This is just more of what we did for the
arms. Note the stack of pelts in the picture on page
245. Every pelt you make is just piled on
top of the rest until you move them. That is what the Pack
Normalize button, shown at the bottom of page 245, is for.
- The picture on page 246 shows all the pelted and relaxed
UVs for the model, arranged in a space saving layout. On page 247, the
Edit UVWs window has been rendered. The render window
has an option to save the current image as a file. Once saved as a
file, the template can be opened in a paint program, and a texture map
for the model can be created. It is important that no further
rearrangement of the pelts take place in the Edit UVWs window once you
decide to create a texture map from that layout.
That is enough of this chapter for now.
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