UV unwrapping and texturing is a lot like papercraft. In order to texture an object, you must first deconstruct it into workable pieces (the head, the torso, the arms etc.), then unwrap them into flat, 2d pieces called UV shells. These shells are organized into a UV map and imported into programs like Photoshop. After texturing, you apply the new texture to your object.
Below is some information about UVs, UV Maps, and UV Shells, explaining what they are and the connection between them each. The Assignment will begin below this explanation. There are several explanation sections on this tutorial. Click the button to expand each for more information.
UV UNWRAPPING AND TEXTURING A DRAGON
For this assignment, you will be UV unwrapping and texturing a dragon model! You will learn the complex process of unwrapping an object, texture the dragon in a painting program, go back and forth between the program and Maya to cover up any scenes, and finally, turn in a rendered image of your custom-textured Dragon Character. There are several complex steps ahead, but don't lose heart! The process of UV unwrapping is routine. We will show you a few different ways to unwrap different shaped objects, but the base process applies with each step.
To make the UV unwrapping process faster, first delete half of the model. You'll then unwrap half the dragon and duplicate the other half over later. The duplicated half will have the same UV layout as the other side.
a) Don't worry about unwrapping the eyes, claws, or horns. Go to the outliner and hide (Ctrl + h) the "HornsandClaws" group until render time.
b) Go to front view, select half the dragon and delete the mesh.
For this dragon, you'll be making UV shells for the tail, face, front of hand, back of hand, upper arm, lower arm, bottom of wing, top of wing, body, leg (can be the entire thing or top and bottom), top of foot, and bottom of foot.
a) Go to the UV Editor (UV → UV Editor under the Modeling menu set). Keep it on the side as you work. This is where you'll be working the most.
b) Select a group of faces on your model that you would like to turn into a UV shell. To help get you started, let's begin by selecting all the faces of the upper leg.
c) You'll notice selecting faces of the geo also selects the faces of UVs in the UV Editor. These selected UVs in the UV Editor need to be grouped together, by using a type of projection from the UVs menu. This will make your initial UV shell.
Now, let's continue making UV shells.
To make a UV shell for the upper leg, let's try a cylindrical projection for the selected upper leg faces. The leg is pretty cylindrical, so this type of projection could work well. *If not, you can try something else. There's no right answer to this.*
Your Cylindrical Mapping Manipulator will most likely appear vertical contrary to the upper leg angle. It's best to have the projection wrap flush around the leg. To fix this, click the little red T on the corner of the manipulator to toggle between scale/rotate/move. To rotate, first click the blue circle on the manipulator to access all the rotation axes.
d) Move the UV shell over to the side in the UV Editor for more space to work. Later on, we will fit all the pieces into the graph in the UV Editor between (1,1) on the axes. For now, it's okay to work outside of this space until all the shells are ready to be organized within the UV Map.
e) Next, you're going to make a temporary checker texture for the newly created UV shell.
This will make it easier to see what parts of the model you've already made shells for
and see any texture distortion on the model when unwrapping the UV shells. It's also good
to keep all the UV shells about the same size, so you can combine UV shells together if need
be. The size of the checkered pattern on the model can show you how much you need to scale
the UV shells so that they are all relatively the same size.
Assign a new lambert shader to the upper leg and name it "checker_mat".
f) Click on the checker square for the lambert's color attribute to bring up a list of color nodes to choose from. Select "checker" node from the list.
g) In the UV editor, you should see the checker pattern in the background of the UV map.
The checker texture on the leg may look distorted, since the UVs aren't made into
unwrapped and organized shells yet. Right now the checkered pattern is a bit too large,
so it's harder to see any distortion. We can fix this by adjusting the way the checker
pattern is repeated on the body.
Go into the Material Attributes for your checker material in the Attribute Editor. Click the arrow next to the Color attribute. Under the UV Coordinates drop down menu, click on the arrow next to Uv Coord.
h) Change the Repeat UVs for both U and V to 15. *Any high number will work.
Let's start unwrapping the upper leg UV shell that was made.
Repeat the previous process to make a UV shell and unwrap the lower leg
NOTE: Your UV shell may look different after the projection, or you might have to unwrap differently
as you continue to follow the directions. That's okay. Unwrapping isn't a linear process where you get
the same results every time. The point in the end is to have a nicely distributed UV shell that's unwrapped,
has proper seams, is the proper size, and ready for a texture.
a) Select the faces of the lower leg.
b) Use a projection to group the UVs of the lower leg together. Cyclindrical Projection should work well for this.
c) Right-click hold on the model and "Assign Existing Material". Select the checkered shader that you made.
d) In the UV Editor, select the lower leg UV shell. Shift + Right-Click and unfold the shell.
e) My UV shell doesn't have a clean seam and looks a bit jagged. Your result might be different. To fix this issue, the jagged UV pieces need to be cut off for a straighter seam.
f) Just like a puzzle piece, the chunk of UVs cut from the shell need to placed on the opposite side and sewn into place.
g) Increase or decrease the scale of the lower leg UV shell so that the size of the square texture is the same as the upper leg.
a) You'll have to examine and decide where the new seam needs to be on the UV Shell.
b) Select the edges where you want the seam to be and cut along those edges. Move one of the pieces of the UV shell to the opposite side and stitch the edges together until the two pieces are one whole piece again.
Make the rest of the UV shells for the dragon and unwrap them.
Once you have all your UV shells made, now it's time for sewing. Make sure the UV shells are all scaled appropriately so that the texture is the same size for all parts of the dragon.
a) You definitely want to start thinking about how you can reduce the seams, since there are a lot of UV shells. For this dragon, it might be best to later combine the wings together, upper and lower leg, arm to hand, and so forth. First move the shells around so that certain parts of the dragon are grouped together that will later be sewn. For example: bottom foot and top foot, arm, top of hand and bottom of hand, upper leg and bottom leg.
WARNING! If you are overzealous in combining shells,
your UV layout and texture may suffer. Some shells probably shouldn't be sewn to other shells, so that they can be larger in scale for higher resolution. So try to strike a balance.
c) Select the edges of shell borders you would like to sew together. Click "Sew Together" tool, and then unfold the newly formed UV shell.
For example, the wings:
The upper and lower hand:
d) In the end, you should have fewer UV shells. In the example, the following groups were sewn together: the upper and lower foot, top of hand bottom of hand and the whole upper arm, upper and lower leg , both wings. The head, torso and tail were not sewn.
Lay out all the shells between 0 and 1 in UV space, then scale and arrange them to maximize the amount of space used. You will also want to leave at least a little space between the shells so that the texture does not bleed between them.
Open the UV snapshot in Photoshop. Double-click the Background layer to convert it to a normal layer. A window will pop up with new layer settings. Name the layer whatever you'd like and press 'OK'.
Your background layer should now look like this:
Create a new layer by going to Layer → New → Layer....
There are several ways to arrange your layers when painting your texture. The simplest is to paint on a layer on top of the UV map. Another way is to place the UV map above your texture layer and set it to "Screen" so that the UVs overlay the paint. Make sure to name your layers.
Paint your dragon however you'd like. It's generally easier to paint in the basic colors, then save out a version of the texture to test in Maya to make sure everything is where you want it. Look for seams, or places where the UV sections are visible in the texture. Try to paint these out if you can. Once you've cleaned that up, it's easier to go back in and add more detail if desired.
If you're not comfortable with Photoshop, or have never used it, here is a link to a reference that has some tips to get you started: How To Use Photoshop.
Back in Maya, create a new material and assign it to the dragon. We will be rendering in Arnold and using Arnold shaders, so make sure the Arnold plugin is installed. This is a good time to apply your shader knowledge from Project 3A! Play with the Ai Standard, Ai Utility, and other shaders!
Then map a File render node into the Color for the material. Browse for your color map in the Image Name field for the file. Since your textures will be .png Maya is going to automatically link them to the shader's transparency channel as well. To get rid of this, disable Arnold's opaque in dragonwhelp_Shape.
Do the same for Bump Mapping and Specular Color if you have bump and specular maps.
a) If you are doing a bump map, you have to separate the shells of your UV map so nothing overlaps. If you are using AI Surface Standard, Bump map will be under geometry. Specular will be under speculate. You can add your images under base --> color.
b) Adjust your textures until you are happy with them. Unfortunately, the texture will not update automatically in Maya when you save a new copy of the texture file. To force an update, go to the file node that you mapped into the Color and click the Reload button.
Open the Outliner. Create a group labeled "dragon_char"and and middle click drag your dragon model into the group. Next, select that group, and hit '3' to smooth it.