Graphics Reference
In-Depth Information
shader that performs operations in
eye coordinates. When object picking
has been enabled, mouse motions in
the window noted above are applied
only to the selected object.
To deselect an object, click in an
open area of the graphics window,
uncheck the Enable Object Picking
checkbox, or close the object trans-
formation area by clicking on the “-”
sign in the buton.
Figure 4.8. A picked object with both axes
and the 3D cursor.
Texture Transformation
In addition, glman gives you a way to change the texture transformation
matrix ( mat4 gl_TextureMatrix[0] ). As this is not something that is done
often, glman has hidden it in a user interface “rollout.” Just click on the “+”
sign in the “Texture (Texture Matrix) Transformation” buton to bring it back
out. The Texture Transformation widgets work the same as the Global Scene
Transformation, Eye Transformation, and Object Transformation coordinate
transforms. Note that using these widgets will not automatically transform
texture coordinates as in the fixed-function OpenGL pipeline. These widgets
just set the gl_TextureMatrix[0] matrix. What you do with that is up to you.
Monitoring the Frame Rate
It is sometimes useful to get an idea of how much certain shader operations
affect the overall speed of the graphics pipeline. For example, certain math
functions are implemented in hardware, some in software; if-tests often cause
a slowdown; and low-count for loops often give beter performance if they are
unrolled. To see what your current frame rate is, click the Display Frame Rate
checkbox in the middle of the user interface window. This makes glman time
your display as you interact with it. After you turn this option on, you will
see two things: (1) a frames-per-second (FPS) number will be presented in the
graphics window, and (2) your display speed will drop sharply. This speed
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