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Applying a texture map to a polygon mesh
Lesson 1: UV texture mapping
Mapping UV texture coordinates
Viewing UVs in the UV Texture Editor
The UV
Texture Editor lets you view and interactively edit the
UV texture coordinates for polygon and subdivision surface types.
UVs appear laid flat within the UV Texture Editor’s 2D view. It
also lets you display the 2D image for the texture map in relation
to the UVs. These features are critical for accurate and efficient
placement of texture maps on polygon and subdivision surface types.
In this lesson, your goal is to ensure that
the shape and placement of the UVs match the image as it appears
in the 2D view of the UV Texture Editor.
This will ensure that the map appears correctly on the cracker box
model in the 3D scene view.
To
open the UV Texture Editor in a two
pane layout
- In
the scene view, right-click any of the Quick Layout buttons
on the Toolbox to display the pop-up
menu of Quick Layout shortcuts and
select Persp/UV Texture Editor from the
list.
The panel layouts update to display the Perspective view
in the left pane and the UV Texture Editor in
the right pane simultaneously. (You can close the Attribute
Editor if it is still displayed.)
This two pane layout is helpful for two reasons:
- The
two view layout shows you how one item selected in the 3D view relates
to the UVs displayed in the 2D view of the UV
Texture Editor and vice versa, without having to open
and close the views repeatedly.
- When
you edit UVs for a surface mesh in the UV Texture Editor,
you can immediately see the effect of the texture map on the model
in the 3D scene view.
UVs do not initially appear in the 2D view of
the UV Texture Editor until you select
an object or change the selection mode for an object in the scene
view.
To
view UVs in the UV Texture Editor
- In
the scene view, right-click any region of the cracker box model
and select Object Mode from the marking
menu.
- Select
the cracker box model.
- In
the UV Texture Editor, dolly the
view outwards so you can see the UVs for the cracker box as shown
below. (To dolly, press the Alt key and drag the mouse to the left
while holding down the right button on your mouse.)
The UV texture coordinates for the cracker box
model appear in the 2D view of the UV Texture Editor as
a flattened, two-dimensional representation. The UVs appear highlighted
with lines connecting the UVs to indicate the region of the texture
the UVs represent.
The image you specified as the texture map for
the box also appears in the 2D view of the UV
Texture Editor in the upper right quadrant of the 2D cartesian
graph called the UV image range or UV
Texture Space. The coordinates for this quadrant range
from 0,0 to 1,1 and represent the texture space for the surface.
How the UVs appear in this quadrant in relation to the displayed
image has a direct bearing on how the texture gets mapped onto the
surface.
TipIf the texture map for the cracker box doesn’t
appear in the 2D view, select Image > Update PSD
Networks in the UV Texture Editor to
refresh the 2D view of the UV Texture Editor.
Update PSD Network is normally used to refresh a PSD texture in
Maya after you have modified the PSD texture in Adobe® Photoshop®.
In this example, the UVs for the cracker box
appear like a box where all six sides have been cut open and then
unfolded flat.
The texture map does not appear correctly on
the cracker box for a number of reasons:
- The UVs for the cracker box extend well beyond
the default 0 to 1 UV range for the texture map in the 2D view of
the UV Texture Editor. As the texture
map displays within the 0 to 1 range, the UVs should also be positioned
to fit within the 0 to 1 UV range, in most cases. Otherwise, the
texture map repeats on the surface mesh, as it does in this case.
- The
position of the UVs do not match the specific regions of the image we’ve
provided for the texture map. The regions of the image show the front,
back, top, bottom, and sides of the box. The UVs should specifically match
these regions to display the texture correctly. UVs do not automatically
align themselves to a texture, you must manually reposition them.
- The
shape of the UVs don’t match the aspect ratio of the cracker box model
in the scene view: -10 (Height) X 8 (Width) X 3 (Depth). This is because
the default UVs for a Maya cube primitive are created based on a predetermined
default shape and do not get updated if the shape or scale of the
primitive is modified later on.
There are a number of things you can do to correct
these issues depending on the situation. For this lesson, you will
correct the UV and texture map misalignment by doing the following:
- Map
a new set of UVs for the cracker box model that better matches the individual
faces of the cracker box. (While the existing UVs could be modified,
you’ll learn how to create new UVs in this lesson that will better match
the size and scale of the 3D model.
- Ensure
the new UVs fit within the 0 to 1 UV range in the UV Texture Editor.
- Reposition
the UVs so that they correlate to specific locations on the 2D image
using the UV Texture Editor. This will
ensure that the various sides of the box receive the correct regions
of the texture map.