Tutorial " Building muscle with XSI
Building muscle with XSI
Summary
Before After
You can use this technique to create muscular biceps or to
deform fingers.
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Tutorial " Building muscle with XSI
Using weight maps with the push
deformer
1. Model the arm in the relaxed position. From the Edit
panel, choose Edit > Freeze to freeze the operator stack.
Draw a two-bone skeletal chain. Select the arm, choose
Deform > Envelope from the Animate toolbar, then pick
your skeletal hierarchy and right-click to end the picking
session.
2. Position the skeleton so that the arm is in the flexed
position to see the effect of the deformation. It should
look something like the  before picture at the beginning
of this tutorial.
3. Select the envelope (arm) and press the t key to activate
Point mode. Now tag (select) some of the points that you
want to be involved in the muscle deformation.
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Tutorial " Building muscle with XSI
4. Choose Get > Property > Weightmap. In the property
editor that opens, rename the weight map to
Muscle_wght.
5. With the Muscle_wght weight map still selected, choose
Deform > Deform > Push from the Animate toolbar.
The Push property editor that opens has the Amplitude
parameter already connected to Muscle_wght. Increase
the amplitude; you will see that the push deformation
affects the points you selected. However, the result is not
very pretty. So lock the Push property editor by clicking
the keyhole icon at the upper right.
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Tutorial " Building muscle with XSI
6. This is where the paint tool comes in handy. With
Muscle_wght still selected, press the w key. You will see
that the envelope now shows the weight map that is
associated with it.
To see the weight maps that are a result of the envelope, select Polygon
Mesh/Clusters/EnvelopWeightCls/Envelope_Weights in the explorer. To
switch back, select Polygon Mesh/Clusters/Point/Muscle_wght. You can
switch between the two weight maps as needed.
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Tutorial " Building muscle with XSI
7. You can use the right mouse button and paint on the
envelope to decrease the weight of the map. You can also
display the Brush Properties page by pressing Ctrl+w. Use
the brush to paint and get the muscle into the shape that
you want.
8. You can now link the amplitude so that it is driven by the
Z rotation of the forearm. To do this, position the arm in
the relaxed position by translating the effector. In the
Push property editor, right-click on the green animation
icon next to Amplitude and choose Link With.
9. In the pop-up explorer, pick the Kinematics\Local
Transform\Ori\Euler\Z node of the forearm bone.
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Tutorial " Building muscle with XSI
10.Now set the amplitude value to 0, then right-click on the
Amplitude icon and choose Set Relative Values.
11.Select the effector and position it so that the arm is in the
flexed position. Now increase the Push amplitude so that
the muscle looks like it is flexed to its extreme. Right-click
on the Amplitude icon and choose Set Relative Values
again.
To see the results I achieved, you can view the AVI file that
accompanies this tutorial. There is also a completed scene
available inside musc_tute.zip.
Tutorial by Jacob Varghese of Softimage Customer Service
Questions & comments: [e-mail]
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SOFTIMAGE and Avid are registered trademarks and XSI
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All other trademarks contained herein are the property of their respective owners.
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