When
texture mapping a polygon or subdivision surface type model it is often
necessary to modify the UV components for a model so they match
the texture map. The UV Texture Editor provides
many tools for working with UVs. In this section you learn how to:
- Select UVs from either the scene view
or the UV Texture Editor and accurately
correlate them. Selecting UV components is critical to modifying them
accurately.
- Sew UV shells together to reduce the
number of UV components you need to work with.
- Move and rotate UVs within the UV
Texture Editor to make the UV shells align to the cracker
box texture map.
Selecting UV components
You
can select UV components from either the scene view or within the UV Texture
Editor. Displaying both the 3D scene view and the 2D
view of the UV Texture Editor lets you
easily correlate which UV components are associated with a particular
edge or vertex on the 3D model.
This is very helpful
to understand the layout and orientation of your UV texture coordinates
in relation to the image used for a texture map and how the map
appears on the model in the 3D scene view.
To select UVs for a 3D model in the scene
view
- In the UV Texture Editor,
select Image > Display Image to
turn off the display of the texture image.
Display Image works by turning the
display of the assigned texture on or off in the 2D view of the UV
Texture Editor. Turning the image off temporarily aids
in viewing only the UV components. This will be useful in the steps
that follow.
- In the scene view, right-click on the
cracker box model and select UV from the
pop-up menu that appears.
- In the scene view, select one UV on any
corner of the cracker box.
Selecting a UV is very
similar to selecting a vertex on an object. That is, you select
a point that resides in exactly the same position as the vertex. When
you select a UV in the scene view, the corresponding UV is also selected
in the UV Texture Editor.
NoteIf
more than one UV gets selected in the UV Texture Editor when
you select a UV in the scene view it indicates that multiple UV
components share the same UV on the 3D model (similar to how polygon
faces share common vertices). This is important to remember when
you move one of these UV components in the UV
Texture Editor and other UVs also move.
- In the scene view, right-click on the
cracker box model and select Edge from
the pop-up menu that appears.
- In the perspective view, select the top
front edge of the cracker box.
When you select this
edge in the scene view, notice that two corresponding shell edges
also get selected in the UV Texture Editor.
This indicates the following:
- The selected edge is shared by two faces;
the front and the top.
- Selecting the top front edge in the scene
view, identifies the corresponding front and top UV shells for the
box. (Indicated by the selection in the UV Texture Editor.)
This is useful when you
need to understand how the various UV shells relate to each other,
especially when you have many UV shells for a model in the scene;
for example, when you sew two UV shell edges together.
In the steps that follow
you select edges in the UV Texture Editor so
you can sew them together.
Sewing UVs
Sewing UV shells together merges the UV shells along
a shared edge that you specify. Sewing UVs is useful for the following
reasons:
- You can move and modify the UV shells
as larger contiguous texture units. This makes it more efficient
to match the UVs to the texture in many situations.
- Texture maps can appear more uniform
across texture borders when the texture is applied to one or more
sewn UV shells compared to many separate UV shells. Sewing shells
together reduces the chance that an unwanted texture mismatch occurs
along the texture edge.
To sew shell edges together in the UV
Texture Editor
- In the scene view, ensure that only the
top front edge of the cracker box is still selected.
When the top front edge
is selected in the scene view, the top edge of one of the large
UV shells is also selected as well as the left side of the middle UV
shell in the top row of the UV Texture Editor.
For the cracker box texture map, you need to sew these together
so they correlate to the map correctly.
- In the UV
Texture Editor, select Polygons > Move and
Sew UV Edges.
The
small rectangular UV shell is repositioned to match the top of the large
UV shell and the two shells are combined into one. When you later select
and move this sewn shell, it will move as one piece. When two UV shells
are selected for sewing, the smallest UV shell is moved to the larger.
- Repeat steps 1 and 2 for the remaining
three edges on front face of the cracker box keeping in mind the
following:
- Select only one edge at a time in the
scene view.
- When you’ve completed the move and sew
operation, your UV Texture Editor should show
the front UV shell with the corresponding top, bottom, and side
shells sewn to it. When fully complete, you will have only two UV
shells to match to the texture image for the cracker box.
- To display the texture borders for the
two shells, select
Texture Border Edges.
(You can also launch this window by right-clicking the Toggle
Texture Borders button on the UV Texture Editor’s
toolbar.)
In the UV
Texture Editor, the texture borders for two UV shells
now appear with a thicker line.
Displaying
texture borders on the UV shells is useful for visualizing where
the texture borders exist on the 3D model in the scene view. That
is, any portion of the texture image that appears outside of the
texture border will not appear on the surface. It is particularly
useful for troubleshooting texture mismatches when they occur. Displaying
the texture borders can also help to identify which UV shells are
combined and which shells are not when you have many UV shells displayed
in the UV Texture Editor.
If you want to be able
to view areas where UV shells overlap in the UV
Texture Editor select Image > Shade UVs.
When Shade UVs is turned on any
selected UV shells appear shaded in a semitransparent fashion. Areas
where the shading appears more opaque indicate the regions of shell
overlap.
In the steps that follow,
you reposition the two UV shells in the UV Texture Editor so
they coincide with the texture image.
Moving UV components
You
manually reposition UV components in the UV Texture Editor using
the tools within the Toolbox. To reposition an individual
UV component you must first select it before selecting the Move
Tool. To reposition an entire UV shell you must first
select one individual UV from the shell it belongs to and then convert
the selection to a shell before using the Move Tool.
To move UVs in the UV
Texture Editor
- In the UV Texture Editor,
select Image > Display Image.
The texture image displays
in the 2D view of the UV Texture Editor dimmed,
as before. You need the image displayed so you can accurately reposition
the two UV shells. Dimming the image aids in seeing the selected
UVs.
- In the UV Texture Editor,
right-click and select UV from the pop-up menu that appears.
- In the UV Texture Editor,
select one UV on the UV shell you sewed earlier in the lesson.
The UV coordinate appears
highlighted in the 2D view.
- Convert the selection to a UV shell by
pressing the Ctrl key and right-clicking in the 2D view of the UV
Texture Editor. Choose To Shell from
the pop-up menu that appears.
The selection changes
from a single selected UV to selecting the entire UV shell.
- From the UV Texture Editor menu,
select Tool > Move UV Shell Tool > .
- In the Move UV Shell Tool options
window, turn off the Prevent overlap option which
prevents UV shells from being moved so they overlap and then select Apply and Close.
The Move
Tool manipulator icon appears over the selected UV shell.
- Drag the green (Y axis) and red (X axis) Move
Tool manipulator handles to reposition the UV shell so
it matches the displayed texture image.
The position of the texture
updates on the cracker box model in the scene view as you do this.
- Select one UV on the other remaining
UV shell.
The UV coordinate appears
highlighted.
- Convert the UV selection to a shell selection
by pressing the Ctrl key and right-clicking in the UV
Texture Editor. Choose To Shell from
the pop-up menu that appears.
The selection changes
from a single selected UV to selecting the entire UV shell.
- In
the UV Texture Editor’s toolbar,
click one of the Rotate UVs buttons to rotate
the UV shell so it appears in the same orientation as the texture image.
(Click the other Rotate UVs button to rotate
it in the opposite direction.)
- Confirm that the texture appears correctly
on the cracker box model in the scene view by tumbling the scene
so you can view the back of the box.
TipIf the texture appears
upside down, you can continue to rotate it another 180 degrees.
If the texture appears reversed, that is, the letters are backwards, you
can correct this by selecting Polygons > Flip from
the UV Texture Editor menu and
choosing the appropriate option setting.
- From the UV Texture Editor menu,
select Tool > Move UV Shell Tool.
A move manipulator icon
appears over the selected UV shell.
- Drag the green (Y axis) and red (X axis)
manipulator handles to reposition the UV shell so it matches the
displayed texture image.
The texture map should
now appear correct on all sides of the cracker box when you’re finished.
TipYou can confirm that
the UV shells are positioned accurately by dollying in closer on
the 2D view of the UV Texture Editor. If a minor
correction is required, simply select and move the UVs or move the
entire UV shell.
TipThe exact UV boundaries
can be viewed more clearly when the anti-aliasing for the texture
image is temporarily turned off. To do this, select
Image
> Display Unfiltered to view the texture image without
anti-aliasing.
If you need to move a
single UV so it precisely matches a particular location on the texture
map you can turn on Pixel Snap (Image
> Pixel Snap). When you select and move the UV using
the Move Tool, it will reposition
the UV coordinate based on pixel boundaries.