UV Mapping – Basics

On June 14, 2009, in Tutorials, by Admin

Creating
a successful UV map usually stems from using a variety of techniques
to achieve the finish results. There are several methods available
to you of unwrapping a mesh. The unwrapping option you choose will
affect the currently selected faces. Bring up the UV Calculation window by pressing U
while in edit mode.
  • Unwrap: Unwraps your mesh based on open edges of a mesh or
    predeclared seams.
  • Cube Projection: Unwraps your mesh based on a Cube Shape.
    Front, Back, Left, Right, Up and Down.
  • Cylinder from View: Performs and unwrapping based on a
    cylinder shape. Unwraps around and then projects a top and bottom.
  • Sphere from View: Performs and unwrapping based on a
    spherical shape. Imagine a basketball being peeled back.
  • Project from View: Sets UV coordinates based on the current
    view.
  • Project from View (Bounds): Same as above, only it will
    utilized the full texture space.
  • Reset: This will restore all UV Faces to either a Square
    shape or a Right Triangle depending on the face.

Cube Projection Example:
Creates a UV map based on a cube
projection. All of the layers are stacked on top of each other here.
Left side, Right side, top, bottom, front and back. This can be handy if you using a repeating
texture and you’re applying it to simple square shapes like boxes or walls of a rectangular room.



Cylinder Projection Example:
Creates a UV map based on a Cylinder
projection. Imagine a pop can being peeled apart. This option is
relative to the current view. In this example, since my view show above
is slightly angled, the unwrapping occurs at this same angle.Resetting my view and performing the Cylinder unwrap again, you
can see the difference it makes on my UV Map.


The unwrapping is also based on the Object’s center. Imagine a line going
vertically through the object’s center and performing a Cylinder
unwrap. You can see the result here if I simply move my Object’s
center to the lower left corner. Performing the Cylinder Unwrap gives
the result shown below.

 



Sphere Projection Example:
With my object’s center reset to the
middle of the object, imagine a line going down through the center of
the object and unwrapping it like a basketball. That’s what is
happening with a Sphere from Viewunwrapping. 




Project From View:
This option basically takes a snap shot of my cube from the current view point and creates
a UV map based on that. What you end up with in this case is the front and back faces
spread out proportionally. The top, sides and bottom map are just squashed together
at the top, bottom and sides of the square in the UV window.




From current view (Bounds):
Same as the previous option, the only difference is that it will utilize the entire UV map
space when creating the UV map.




Unwrap (smart projections):
Creates a UV map while doing it’s best to unwrap the mesh for you. Although
it creates a map that is as flat as possible, it’s broken up quite a bit and there’s
nothing symmetrical. Some uses I see for this would be to create a quick map for the
sole purpose of baking a Bump Map or ambient occlusions. Possibly, if you are simply
planning on painting your object directly and need a quick map, this would work as well.


Creating Seams:
I suppose the main goal of creating a good UV map is getting your objects ‘skin’ laid
out as flat and as evenly as possible so your texture will not look distorted when applied.
Just do your best. One step to creating a good mesh will be creating your own seams on
your model. This tells Blender where it’s ok with you to split or cut the mesh apart when
creating your map. To create a seam, simply select the edge(s) where you want it and
press CTRL-E to bring up the Edge Specials menu. Select the first option,
Mark Seams, to create a seam. The edges marked as a seam will retain an differnt color
than the edges that are not seams. With my current Blender theme, my edges are marked in
orange.Another valuable tool to use are the UV Pins. You can imagine those as actual
pins that you can stick in your UV map that will hold that section in place the next time
you Unwrap it. These are located in the UV window. Select UVs from the menu bar and
you will see them listed. Pin – pin’s the selected vertices. Unpin will remove the pins from
the selected vertices. Pinned vertices are usually marked with a larger red square in the UV
window.

Mapping the Monkey:
Let’s try making a map for Blender’s Monkey object. There’s no right or wrong way to
do it. It’s up to the artist.
My first thought when I decided to make a uv map for this object, was to separate the
face from the rest of the head. From what I remember, monkeys’ faces are usually hairless
and have a different color than the rest of the head.

I started by selecting a line of edges that would circle his face and created seams for
them. The procedure is simple. Select edges, Mark as seams and continue. I did this
all the way around the side of his face.
When I was finished. I selected all of the faces (edges), press U to bring up the UV Calculation Menu
and selected the first option from the
UV Calculation menu ‘Unwrap‘.

The first result here looks really good so far. You can see the face in the lower right hand corner.
It looks really even and proportional and I think I’ll keep it just the way it is. The
eyes are fine as well so I’ll leave them as they are. The rest of the head still needs some
work.

Another technique I use is to create vertex groups for different areas of the map so I can select them
or hide them if I wish. You could use different materials if you wish as well, but there’s still
the 16 material limit per object. Once you have an area of your map the way you like it,
you can select it and hide it (H) to make it easier to work with the rest of your map. To
un-hide every thing, press ALT-H.

  • I selected my face here, clicked ‘New‘ under the vertex
    group section and click ‘Assign’ to assign them to the new vertex group.

Next step, I think we’re going to have to separate the ears from the rest of the head.
Select some edges around the base of the ear that form a loop and mark them as seams.
Do this for each ear. Select each ear and create a vertex group for them. Hide them for
now so we can work on the rest of the head. We’ll get back to the ears in just a bit.


Here is the remainder of my monkey’s head with the face and ears hidden. Unwrapping (U, Unwrap)
the mesh at this point will give you the result shown below:

Basically, what happens is the opening where the face was gets stretched way out in order
to flatten out the rest of the head. The sections closest to the face get stretched out and
the areas down the center of the head end up much smaller. Adding more seams may give you
a smoother result. The only down side to adding more seams is that it gives you more areas
of the mesh that you’ll need to line up two edges that meet.

I’ll try adding a seam on each side of the head between the face and the ear holes.
Three edges on each side I’ve marked as seams. Let’s try unwrapping again and check our results.

With this Unwrapping, the result is a little more satisfactory for me. The faces seem to be
closer to their actual proportions so I’m going to keep them as they are.

  • Another thing that I do when I’m mapping is move sections of the map off of the texture area
    in preparation of organizing them all together at the end of the process.

Move each section to an area that you know is vacant of other uvmap sections. I’ll move the
map of my head off of the top of the texture area.


Going back to the map of my face and eyes, I move these down off of the bottom of the texture
area.This just leaves us with the ears to deal with.


The inner ears will be skin colored, so I’ll just select those, do a simple Unwrap to flatten them out.
Create an inner ear vertex group and assign them to it for easier selection later. I’ve moved these
off the top right of the texture area. Then hide them (H) to make it easier to work with the
remainder of the ear.


The rest of the ear, I’ll just go with a simple Unwrap again and move them off to the
right / bottom of the texture area. Scale them down a bit making sure they won’t be
overlapping any of the hidden UV map.


Let’s put it all together now. Un Hide your entire mesh (ALT – H). Select all
of the face on our model in order to see them in the UV window. Select each section from
the UV window and move them into the texture area. Scale them and rotate them as needed
in order to get all sections onto your texture area.


Here’s the basic idea. Group everything back on to the texture area. Try to utilize your
complete texture area. It’s also a good idea to try and keep things proportional with each
other. The larger the section of the map is the more detail you can add to it.


When you’re satisfied with your map, you can save it via the UV menu bar option.
Go up to Scripts and then Save UV Face Layout.Now with some simple texturing, you’ll end up with a nice looking monkey.


My simple texture map and the final result shown below.


Hope this helps everyone.
Scott
 

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