Graphics Reference
In-Depth Information
Eye Transformation
These widgets are the second set of transformation widgets
in Figure 4.6. They let you transform the entire scene in the
graphics window. Unlike the Global Scene Transformation
widgets above, however, these transformations
do
end up in
the ModelView matrix, just as if the OpenGL
gluLookAt( )
routine had been called. That is, these scene transformations
change the Eye Coordinate behavior of the shaders.
To repeat something we said at the start of this chapter,
unless you initially translate your geometry in the negative
Z
direction in the GLIB file, your first move upon opening up
a new GLIB scene is probably to use the “Trans Z” widget in
the Eye Transformation group to push the scene back into
the viewing volume, where it is more visible. You can use the
.glib LookAt command to do this as well.
Object Picking and Transformation
Individual objects in the scene can be picked and indepen-
dently transformed. This is a good way to test shaders that
operate in eye coordinates rather than in model coordinates.
In order to use this functionality, just click on the “+” sign
in the “Object (Individual Matrix) Transformation” buton to
bring it up. To remove it, click on the “-” sign in the buton.
To be able to select an object, you must enable object
picking by turning on the Enable Object Picking checkbox
shown in Figure 4.7. Then clicking on a 3D object in the scene
with the left mouse buton will cause that object to be selected,
as shown in Figure 4.8. A large 3D cursor becomes centered
on the object to show that it is selected.
Figure 4.6.
The interface win-
dow with the transformation
functions.
When an object has been
selected, the Object Transformation
widgets shown in Figure 4.7 will
become active. These widgets will
apply transformations to the selected
object separately from all other
objects in the scene. The object trans-
formations go into the
ModelView
matrix for the one picked scene
object, where they will impact any
Figure 4.7.
The expanded Texture and
Object Transformation area in the inter-
face window.
