Lesson 2: Painting Sticky weights to bones

Open the scene for the lesson

1. Load the scene you worked on in the previous lesson or load the DragonLeg_Paint_Start.mb file from the Lesson 2 folder.

   This scene contains the dragon leg with connected bones and capsule objects. The dragon leg mesh is set up with default Sticky weights applied to the capsules for basic skin deformation.

   You can use the Display Layer Editor to show and hide various parts of this rig.

Paint weights

After you apply default weights to the bones and polygon mesh objects, you can use the Muscle Paint window to refine those weights, increasing or decreasing the effect of the default weights.

1. In the scene view, select Shading > Smooth Shade All, if it is not already on.
2. Select the skin mesh object (pSkinMesh) then select Muscle > Paint Muscle Weights.

   The Muscle Paint window appears and the mesh appears in Paint mode, in a black color.

   The Muscle Paint window provides many of the same basic features as the Artisan paint tools. See Muscle Paint tool in the Maya Muscle guide to learn more about its specific attributes.

3. Set up the Muscle Paint window as follows:
   • Select Sticky from the Weights drop-down menu.
   • Select jntShoulder in the Influence list.
   • Turn on Replace.
     
4. In the dragon leg hip area, paint weights to the jntShoulder (hip) bone.

   Wherever you paint, the default weights are replaced with the weight value you are painting (by default, 1). You can adjust the Weight value in the Muscle Paint window and continue painting.

   Tip

   Press and hold the b key while dragging in the scene view to adjust the size of the brush.

   
5. When you are finished painting weights, close the Muscle Paint window.
6. Scrub the timeline to see how your painted weights affect the way the skin deforms as the bones move.

   In the next steps, you set weights on specific points, rather than painting them on the entire upper leg.

Set weights to specific points

1. Open the Muscle Paint window and select jntLegUp in the Influence list.
2. Turn off Paint mode in the Muscle Paint window.
   

   The painting features are now disabled in the Muscle Paint window, and the points of the skin mesh appear.

3. Select the specific points on the upper leg where you want to set weights.
   
   Tip

   Use the Lasso Tool for more precision when selecting points.

   Notice that the Live Update option is on. This means that as you drag the Weight slider, the weights update interactively. When Live Update is off, you can set the weight value, but the weight does not change until you click Set Weight/Flood.

   When you have multiple points selected and Live Update is on, the Weight slider automatically adjusts to show the average weight to the current object for the selected points. For example, if you select some points where the mesh is black and some where the mesh is red, the Weight slider shows the average value of those points.

4. Use the Weight slider to drag the value to 0.5. Notice that the color turns yellow to show this area has half the weight.
5. Continue dragging the slider up to 1.0. The selected points on the dragon leg mesh are now weighted 100% to the upper leg bone.

Smooth weights

In the next steps, you will smooth the transition between the shoulder (hip) and upper leg joint. To make sure weights don’t get re-normalized to other bones, you can lock weights.

1. Clear your selection by clicking an empty area of the scene, then turn Paint mode on in the Muscle Paint window.
   Note

   It's important that you have no points selected when you turn Paint mode back on. If you turn Paint mode on with some points selected, only those points are paintable. When you turn Paint mode on with nothing selected, the entire mesh becomes paintable again.

2. In the Influence list, select everything except for the jntShoulder and jntLegUp bones, then -click and select Enable Lock/Hold Weights on highlighted items from the pop-up menu.

   A HOLD marker appears next to each joint, meaning the current weights for those items are locked and cannot be adjusted, even if you paint around that item. You can now safely smooth weights between the shoulder and upper leg only, since those are the only two joints currently unlocked.

3. Select jntLegUp in the Influence list, and turn on Smooth.
4. Paint along the top edge of the upper leg a few times.
   
5. Scrub the timeline to see the smooth deformation between the shoulder and upper leg.
6. Select all the items in the Influence list, -click and select Disable Lock/Hold Weights on highlighted items to continue painting on other bones.
7. Continue to paint and smooth weights to the joints/capsules for basic rigid bone skinning with the techniques you have learned in this lesson. Leave the weights on the polygon knee cap and blade at zero, as you will use those objects for Sliding effects in a later lesson.

When you are finished, you have a basic skin setup with bones. You can find the completed file for this lesson, DragonLeg_Paint_End.mb, in the Maya Muscle Advanced Techniques folder.

Beyond the lesson

In this lesson you learned how to:

• Paint sticky weights to bones using the Muscle Paint window
• Apply weights to specific points on a mesh
• Apply Smooth weights for better transition between weights

Painting Sticky weights to bones or capsules gives an effect similar to Maya skinClusters. The other main features of using the Muscle skin deformer, such as Sliding and Jiggle, are discussed in the following lessons.

In general, it is recommended that you first paint weights to only the capsules and bones on your mesh before working with muscles and Sticky weights. This can help keep your weighting structured and organized.