 | For this tutorial we are going to use a cartoon-style model of a mobster.
This model has been provided by Viewpoint. It was
modeled with 3D Studio.
Click here to download the Mobster
model in 3D Canvas format.
BioVision has a number of sample motions available
at their website. Click here to
download the walking motion that we used to create this tutorial. Click here (497K) to view an
animation created with this BioVision file. It is something of a gorilla-style walk which
seems appropriate for the model. |
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 | The BioVision Hierarchy (bvh) file was created using a human so the body parts will not
match our cartoon character. We will need to do a considerable amount of resizing. This
will be easiest if working with a couple of views of the character model.
Select View Selection from the View menu. Choose the
icon that indicates two vertical-oriented views.
Right-Click on the right view, and select View->Orthographic->Front
from the popup menu
Also we will be working with animation key-frames, so show the Animation Toolbar using the
View menu. |
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 | To resize the BioVision animation information to fit our skeleton will require some
estimation and a little bit of trial-and-error.
The first step is to do a trial import of the animation information to see how it compares
with our character model.
Select Import->BioVision Motion Capture (bvh) from the File
menu.
Find the motion capture file that you want to import.
There are a number of options provided for BioVision imports. Importing BioVision files
can be time consuming. Since this is simply an import test we only need to import one
key-frame of the animation. Enter a key frame range of 1 to 1 in the Include Keys:
fields and click OK. |
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 | 3D Canvas created a skeleton made up of Limb Placeholders from the BioVision file.
These placeholders are temporary body parts that you will eventually replace with the body
parts of your character.
This skeleton is far too large for our character. The important thing to remember when
importing BioVision files is that the length of the legs of the character must match the
length of the legs of the BioVision skeleton. This ensures that the character's stride
will be correct.
There are two options here, you can increase the size of the character to match the
skeleton, or you can reduce the size of the skeleton to match the character. For life-like
human characters this is usually an easy task, since the length of the limbs will
typically match fairly closely. But for our cartoon character this is going to be more
difficult.
Increasing the size of the character model is easy. Simply alt-click on the root of the
model (usually the hips) and ctrl-drag to scale.
Reducing the size of the skeleton after importing isn't really practical since it would
require repositioning each bone at each time interval in the animation. This is a job that
is too large to be done post-import. The solution is to change the size of the model
during the import. The BioVision Import options provide options to resize the skeleton
during the import. |
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 | A BioVision import creates a "pedestal" for the imported skeleton. This is
simply a flatted cube that indicates the start position of the animation sequence. This
pedestal can be used to move the imported skeleton and animation sequence to a new
location and orientation. It also can be used for deleting the entire imported skeleton.
Alt-click on the pedestal and select Delete from the File
menu to delete the imported skeleton.
Re-import the skeleton, this time however select a Percentage of Original Size
of 30% as well as Include Keys: of 1 to 1.
30% isn't a magic number. By comparing the imported skeleton with the mobster model I
estimated that I needed to reduce the size of the skeleton to 35%. A couple of trial
imports later I hit on the ideal import percentage of 30% to give the correct leg length.
Note that you could have left Percent of Original Size at 100% and
entered 30% for each Joint/Bone in the Hierarchy Components but that would have been
incorrect. That would not have resized the animation position. It is essential that Percentage
of Original Size be set such that the length of your character's legs match that
of the imported skeleton.
We now have an imported skeleton with correct leg lengths. Unfortunately, that seems to be
the only thing that is correct. Since we have a character whose body shape is a caricature
of a real body we will have to do considerable resizing to fit. If we were using a
character based on the real world, we might be done resizing.
In the next step, we will adjust the width of the hips. From the import it appears that
the hips need to be about twice as wide as they are. That means they should be imported
with at 60% (2x 30%) of the original size to get the right width. I did a couple of trial
imports to determine the correct width of 55%. |
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 | Delete the previous skeleton.
Re-import the skeleton, this time however select a Percentage of Original Size
of 30% as well as a Include Keys: of 1 to 1. Also, this time go to the Hierarchy
Components section and enter 55% for LeftUpLeg and RightUpLeg. The percentage
entered in the Hierarchy Components section adjusts the relative position of a bone. Since
we want to adjust the relative position of the hip joints, we adjust the position of the
upper legs.
I have hidden a few items in this view of our character to make it easier to see the area
we are working on. You can do this also by right-clicking on them and de-selecting Visible.
To make them visible again click and on the Primary Toolbar. |
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 | The placeholders of the leg are not oriented properly. Re-orient them using the Edit Control. This is a good test to see if they are the correct
length. In this example they are not.
Delete the skeleton, and re-import selecting a Percentage of Original Size
of 30% as well as a Include Keys: of 1 to 1 a LeftUpLeg/RightUpLeg amount
of 55%, a LeftLowLeg/RightLowLeg amount of 25% and a LeftFoot/RightFoot amount of 35%.
Again, these numbers were found by estimation and then trial and error. |
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 | Re-orient the placeholders of the leg using the Edit Control.
They should be the correct length now. Note that we do not want to reorient the foot bone
in the direction of the foot. It is in-line with the calf bone and that is what the
creator of the BioVision file intended.
Every time you delete an imported BioVision hierarchy and re-import you will loose the
orientation of the place holders, so don't spend a lot of time in this stage perfecting
orientations. |
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 | Repeat this technique for all the remaining placeholders of the animation. For those who
want to skip this step of estimation/trial-and-error bone length determination, I found
these to be good percentages:
Percentage of Original Size: 30
Hips: 30%
Chest: 50%
Neck: 39%
Head: 30%
LeftCollar/RightCollar: 44%
LeftUpArm/RightUpArm: 120%
LeftLowArm/RightLowArm: 45%
LeftHand/RightHand: 40%
LeftUpLeg/RightUpLeg: 55%
LeftLowLeg/RightLowLeg: 25%
LeftFoot/RightFoot: 35%
Import the entire animation including all key-frames. In other words, don't change the Include
Keys: fields this time.
Re-orient the placeholders as appropriate using the Edit Control.
Take care to do as little rotation as possible to achieve the desired orientation. I found
with this model that I had to orient the Neck and Head backwards to get an acceptable
result. |
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 | It is now time to move the character's parts from the original frame hierarchy to the
new frame hierarchy.
This means moving each part one-by-one from the "Al" hierarchy to the
"Pedestal" hierarchy.
In the example on the right I have moved the Torso-Lower from the "Al" frame to
the "Pedestal/Hips" frame. The next step will be to move the Torso-Upper, Coat
Buttons, Tie and Shirt from the "Al/Torso-Upper" frame to the
"Pedestal/Hips/Chest" frame.
Repeat this process for all of the remaining character parts. Close unused frames as
needed.
Also, delete all of the bones of the original model since that frame hierarchy is no
longer needed. |
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 | We now have a BioVision animated Character.
Switch to Animation Mode by selecting .
Press play to
preview the animation. |
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 | The placeholder objects can now be removed if you wish. They were simply placeholders
for the character's body parts so they are no longer needed. |
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 | Use the pedestal to position and orient your animation.
Once you have done this, you can delete the pedestal. |
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 | The information used by 3D Canvas to properly shade objects may be affected by moving
body parts from frame to frame.
To correct this apply a Crease operation to each body part.
Click here (142k) to
view an animation created with this model. |
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