How to create an arm bulge in 3ds max? (Muscle deformation technique)

Detailed tutorial to create a semi-realistic arm bulge in 3ds max with Muscle deformation technique.

In this tutorial, I am going to show you how to create a semi realistic arm bulge in 3ds max. It’s a quite handy technique to create believable deformations. If you find muscle bones technique difficult or time taking then you can use this technique instead.


Here I have a low poly skinned arm geometry having a simple 40 frames animation.

The hand is going from the normal position (Frame 0) to the bend position (Frame 20). As you can notice when it goes from normal to bend position it gives very weird deformations.

We will convert this weird looking deformation to a clean and believable deformation with this technique. So, let’s get started.


arm bulge in 3ds max

Let’s first select our mesh and add Skin Morph modifier to it and under Parameters rollout, click on Add Bone button and choose forearm bone from the list.

Note: Skin Morph modifier should be at the top of the Skin modifier. Do not add it below the Skin modifier.


arm bulge in 3ds max

At frame 0, when arm is at normal position, click on Create Morph button (Local Properties) and name it Normal.

Step 3

arm bulge in 3ds max

Now, at frame 20, when the arm is bending completely, again click on Create Morph button and name it Bend.

Step 4

arm bulge in 3ds max

Now, Select the Bend morph and click on Edit button (Local Properties) and start defining the bicep muscle to create the bulge by tweaking the vertices.

Tip: Under Selection rollout, turn on Use Soft selection option to make tweaking little bit faster and easier.

Step 5

arm bulge in 3ds max

We can remove the extra vertices that are not involved in the morphing process. To remove the unused vertices, select the vertices that you want to remove then go to Local Properties rollout and click on Remove Verts button.

Tip: To make selection process easy, use Paint Brush Selection while selecting the vertices.

Step 6

Here is the final result. You can check the setup by moving the arm to see if morph is working correctly or not. Mine is working fine with default settings but if you want to tweak your setup to get the best results then have a look at some points given below.

Few things you need to know

FallOff Settings: You can tweak falloff settings of the selected morph. Under Local Propertiesrollout, you will find an option called Falloff. There are five types of falloff graphs:

  • Linear (default)
  • Sinual
  • Fast
  • Slow
  • Custom Falloff (User defined)

arm bulge in 3ds max

If you want to use Custom Falloff, just select Custom Falloff from dropdown and click on “G” button to bring up the graph. Now under that small graph editor window, define your falloff curve. Now your morph will react according to that falloff curve. Default falloff (Linear) is working fine for me.

Influence Angle

You can also adjust the Influence Angle of the selected morph. Again I am using the default value (90.0) for influence angle.

Influence angle is the angle at which your morph starts influencing the mesh.

Difference between Ball joint and Planar joint in Skin morph modifier

  • Ball Joint: Ball joint tracks bone’s rotation in all the three axes. The below given example uses ball joint type and notice how morph is responding to the every rotation of the bone.

  • Planar Joint: Unlike ball joint, planar joint detects bone’s rotation only in the plane of it’s parent bone. The below given example uses planar joint and you can easily notice that the morph is responding only when forearm bone is rotating in the plane of it’s parent bone (arm bone).

That’s all. Hope you like this tutorial. You can use the same technique to create other complex deformations of hip joint, neck twist or any other part of the body. Have trouble following this? Leave comments or throw me an email. Good luck!