Jahirul Amin provides step-by-step tuition and over 2-hours of video guidance for adding corrective blend shapes in Maya
to download assets to accompany this tutorial
Maya rigging: Introduction to rigging
Maya rigging: Introduction to rigging a human torso
Maya rigging: Introduction to rigging the neck and the head
Maya rigging: Introduction to rigging the shoulder and the arms
Maya rigging: Introduction to rigging the hands
Maya rigging: Introduction to rigging the legs
Maya rigging: Introduction to rigging the feet
Maya rigging: Introduction to rigging the fingers and thumbs
Maya rigging: Introduction to cleaning up the rig
Maya rigging: Introduction to skinning
During this tutorial we will be adding corrective blend shapes on top of the skinning we did previously. Blend shapes will allow us to push deformation much further than can be achieved through skinning alone. Before blend shapes can be added, however, it is essential that the skinning is as refined as you can get it in order to provide sound foundations for your additional work; corrective blend shapes are not a solution for overly hasty skinning.
To speed up the process of creating the corrective blend shapes, we'll be using 2 scripts: the abSymMesh.mel script by Brendan Ross
and the BSpiritCorrectiveShape.mel script by Christian Breitling
. I'd like to thank both Brendan and Christian for giving me permission to use and also supply the scripts for this tutorial as they proved to be lifesavers. For the most part, we'll be using the general Maya tools to re-work the poses but I'll also demonstrate how you can use Mudbox to aid the process. Maya plus the use of scripts or plug-ins work fine, but sometimes I find it easier to use the sculpt tools that Mudbox or indeed ZBrush offer to correct a pose.
Using the scripts
Before cracking on, I just want to make a quick note of some of the changes I've made since last time. Firstly, I've deleted the history (Edit > Delete by Type > History) from the pants, which will in turn kill off the Wrap Deformer. There was nothing wrong with using the Wrap Deformer at this time, I just wanted to keep the scene as light as possible for now. I can always add this later on or I may even consider using a cloth setup to add more believability to the pants. I've also spent a further hour or so, refining the weights for the main mesh by using the Weight Hammer tool to push some of the pesky vertices back into shape.
Now a quick explanation of the 2 scripts we will use. The first script is the abSymMesh.mel script by Brendan Ross. At the click of a button, this script will allow you to build symmetrical blend shapes, check that your model is symmetrical and much more. Here's a quick breakdown on how to run and use the script. In the Script Editor (Window > General Editor), create a new MEL tab (Ctrl+T > MEL), go File > Load Script and then select abSymMesh.mel. (You'll find this in the Scripts folder within the project directory supplied with this tutorial). With the script loaded, hit Ctrl+A to highlight all the text and then hit Enter on the Numpad to source the script. Now highlight the words 'abSymMesh' on the second line of the script and hit Enter on the Numpad to create the GUI. If you like, you can also MMB-drag the highlighted text (abSymMesh) onto a Shelf so you no longer need to pop into the Script Editor to run it. We'll cover how to use the script later on when we come to creating our corrective blend shapes.
The next script is the BSpiritCorrectiveShape.mel script by Christian Breitling. This tool will allow us to pose our mesh into a problematic position, sculpt the corrective fix in that problematic pose, and then through some vertex magic, it will extract the difference between the vertices of the bind pose and the vertices that have since been affected, to create the corrective pose. Hopefully, I've explained that clearly, if not, check out the video that will give you a better example of what the script does. Load the BSpiritCorrectiveShape.mel script into a MEL tab in the Script Editor, highlight all the text and hit Enter on the Numpad to source it. To run this script, we'll need to have 2 meshes selected (the corrective pose and the original pose) and then we'll need to run the 'BSpiritCorrectiveShape' command. If you like, you can also MMB-drag this command onto the Shelf to speed up the process of running the script. The process will be more fully explained as we go through the tutorial.
If your mesh is not symmetrical, forward to Top Tip 1 which covers how to make it so.
The two scripts that we will be using in this tutorial to speed up the process of creating corrective blend shapes