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13.3 Skelegons - Part 3
 
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MODELER, WEIGHT MAPS

If you have closed the last version of the arm that we did in the last tutorial do a 'File->Close All Objects' (to make sure that multiple objects aren't accumulating), then do a 'File->Open Object...' and choose arm_03.lwo.

And, as usual, it is best to instantaneously do a 'File->Save Object As...' and bump the number to arm_04.lwo.

In the last tutorial, I created three skelegons and their associated Weight Map names, but didn't fill them in with any weighting information.

To see a weight map, go to the 'Perspective' viewport and from the view type drop-down menu choose 'Weight Shade'


If I choose the 'ArmShoulder' Weight Map from the Weight Map drop down at the bottom right of the window...


The arm's polygons are displayed in an army green color, indicating that no polygons are yet associated with that weight map.



IMPORTANT - Although you might have had Modeler automate Weight Map creation for you as you created each bone, each Weight Map will be empty until you define it.

Weight values are given to points, not polygons. Thus, I have to press CTRL-g to enter 'Select Points' mode.

To define points to be associated with a certain Weight Map, you first select all points that you wish to have the same Weight Value.

Turn off subsurface mode by pressing TAB before you work with weight map values. It becomes sluggish when you're working with the Subsurface mode turned on while in the Weightmap view type.

I'll start with the first row of points up by the shoulder. It doesn't matter what order I select the points.



From the 'Weight Map' drop-down menu I select '(new)'.



I wish to associate these points, with a 100% weight value, to the 'ArmShoulder' bone. I select the Name 'ArmShoulder' from the 'Create Weight Map' drop-down menu, keeping all of the default values and making sure that 'Initial Value' is checked.


Once I click 'OK', the weights for those points are applied.



The brightest red value means that a movement of the associated bone would make a very strong connected movement with those points.

A very light red indicates that the influence of the bone drops off by that percentage at that relative position in the object.

I deselect the first row. To select the second row of points, it will be helpful to choose the 'Wireframe' view type in the 'Perspective' viewport.

I use ALT and the left mouse button to rotate the row, and when I can see each point, I SHIFT-select the next point until all points in that row have been selected.



I again pick '(new)' from the 'Weight Map' drop-down menu, again select 'ArmShoulder' as the Weight Map to add these points to, and enter 50% as the value.



Here's the time to say some things about what you're doing when you're selecting '(new)' to bring up the 'Create Weight Map' requester.

1. When you select '(new)', that doesn't necessarily mean that you've never defined that weight map before.


2. You can select names from the drop-down menu while you're in the 'Create Weight Map' requester without modifying whatever name you select.

IMPORTANT - NO CHANGES WILL BE ACCEPTED FOR WEIGHT MAPS UNTIL YOU'VE PRESSED THE 'ENTER' KEY OR CLICKED 'OK'.

3. You can select names from the drop-down menu, modify the name in the 'Name' gadget box, and that newly typed name will be taken as a new weight map name once you click 'OK'.

This makes it handy when names are similar and you don't wish to have to type the whole name every time you create a new weight map.


4. You can type new percent values without typing the percent sign.

If you click in the 'Name' box after you've typed a number in the percent gadget box, a decimal point, a zero and a percent sign will automatically be added to what you typed.


5. Placing a checkmark on 'Initial Value' seems to do nothing.

Whether you have this checkmarked or not, new points are added to old points and new values for old points replace old point values.


6. When you define new points which weren't in the last weight map definition you did for that weight map name, any new points you add will be combined with the old weight map point definitions creating a weight map definition which combines both sets of points, the old ones and the new ones.


7. Any points which are the same points as you had in an old weight map definition will be replaced by the new point value you give it.


8. Clicking 'Cancel', without either pressing 'ENTER' or 'OK' will halt any changes you've made in either a weight map name, or point value.


I click 'OK' to have Modeler merge the new point values with the old point values.

The old points that I had originally defined will still be the same as they were (unless one of the old points was the same as one of the points I just added).

...and the second row of points will be merged with the Weight Map definitions with a lower 50% value.

Since 'Wireframe' is the current view type, nothing seems to have changed. However, when I select 'Weight Shade' from the view type drop-down menu...



I can now see that the weight drops from 50% to 0% between the second and third rows instead of 100% to 0% as it had after defining the first row.



I again enter 'Wireframe' as the view type, selecting the third row (it's getting harder to see which points belong to which row).



These points, I'll set with a 10% value for the 'ArmShoulder' Weight Map, but I'll also set them with a 20% value on the 'ArmBicep' Weight Map.

IMPORTANT - Any point may be associated with more than one weight map.

To do this, I first choose '(new)' as I've been doing, select 'ArmShoulder' from the 'Create Weight Map' requester, type in 10% as the value.


I click 'OK'.

I switch to 'Weight Shade' view type. You can only see a slight gradation between the third and fourth row of points as it now gradates from 10% to 0%, which is a very small amount of gradation.



Without touching any of the points, I again pick '(new)' to bring up the 'Create Weight Map' requester, pick 'ArmBicep' from the drop-down menu, type 20% as the value.



When I click 'OK', the weight shows the first row of the newly begun 'ArmBicep' Weight Map.



I switch again to 'Wireframe' view type, carefully selecting the fourth row of points. I select '(new)', pick 'ArmBicep', and give that row a value of 50%.


Switching back to the 'Weight Shade' view type...



I select the fifth row while in the Wireframe view type.



I switch to 'Weight Shade' view type.


I keep doing this, choosing the 6th row, giving it a value of 75% for the 'ArmBicep' Weight Map and 25% for the ArmForearm Weight Map.

I choose the 7th row, giving it a value of 50% for the ArmBicep Weight Map and 50% for the 'ArmForearm' Weight Map.

I chose the 8th row, giving it a value of 25% for the ArmBicep Weight Map and 75% for the ArmForearm and so on, tapering the value higher and lower as I go.

The Weight value should be strong in the middle of the bone, and drop off to zero on the ends.

Here's what the 'ArmBicep' Weight Map looks like when its done...


So the arm bends, smoothly, always overlap weight maps so the 'ArmForearm' influence extends into the area of 'ArmBicep' influence.

IMPORTANT - The biggest problem that people run into is when they don't define a Weight value for a particular point. If no Weight Value is given for a point, it will stay where it is (not being influenced by any bone when bones move).

If you ever move a bone, and part of the object stays behind, that point has not yet been given a Weight Map value.

Here's the 'ArmForearm' Weight Map:


You should taper your weight maps in a 20%, 50%, 100%, 60%, 40%, 20% or a 25%, 50%, 75%, 100%, 75%, 50%, 25% manner.

The best thing to do is experiment. Over time you'll get good sense of the taper that should be used, and what associated values are most effective.

I press 's' to save the object.


MODELER, TAPERING ONE BONE INTO ANOTHER

When the weight values of two bones overlap, the additive value of each bone should add to 100%.



MODELER, DETERMINING POINT'S WEIGHT VALUE

If at any time you wish to determine a point's weight value, make sure you're in the 'Point Select' mode by pressing CTRL-g, select the point you wish to know the weight value of and press 'i' to bring up the 'Point Info' panel.

Click the white arrow to the left of the bone's name the point should be associated with and a menu will unfold showing the point value for that bone.



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