Muscle Line Mapping

Muscle Line Mapping

Let's start working. Load the last file you saved in Chapter 2, called Kila_Basic.mb.

Look at your character model (Figure 3.1). So far, it's quite well defined and the proportions are correct. It is a good base model. In fact, with a bit of optimization, you could use her as a low-resolution character just as she is. She would not, however, be good as our main model. We still have a few problems to address:

  • Taken statically, she looks fine, but once you start to animate her, the flaws will show. There will be breaks or bulges in the areas that bend, either because they don't have enough polygons or because the topology needs some work.

  • The mesh as it stands has too many polygons that simply are not needed.

  • She lacks physical detail in both her body and face.

  • This model still has no hands or feet.

Figure 3.1. Our base model

Our first step is to physically map the muscle groups onto the mesh. Doing this gives us a good understanding of how the mesh will move. In turn, when we animate the model, the polygons will deform, giving the illusion of muscles deforming under the skin. While we are adding these lines to the mesh, we can also add detail, giving additional shape to the geometry while we check its deformability.


A lot of detail can be gained through the texture map (more on this in Chapter 9, "Texture Painting"). Try not to get too caught up in building small details into the geometryyou'll just use up processor power, meaning fewer polygons can be used elsewhere in the game.

Use Figure 3.2 to guide you in placing the muscle lines on the mesh. This illustration shows a simplified version of the muscles. All we need is a basic idea to work with; at this point, we're just implementing the main muscles.

Figure 3.2. Basic muscle lines of the human body

We will start at the top and work our way down, but we will skip the head for now and concentrate on that area later in the chapter. So select the left side of the mesh, and let's get started.

The Neck

Refer to the neck in Figure 3.2. You can see two large muscles coming from the ears and ending where the collarbones meet in the center of the chest. These are the sternocleidomastoid muscles. Let's add these to our model.


We are going to split the polygons around the neck, carving these muscles into the mesh. Start by going to Edit Polygons > Split Polygon Tool.


As you did in the preceding chapter, click and hold on the starting edge around where the ear should be. A small icon appears, representing the starting point of the cut. Move the point up until you are at the corner where two edges meet, and release the button.


Select the point on the next edge where you wish to cut, and press Enter to finish that cut.


You need to work your way around until you get to the collarbone, as shown in Figure 3.3. You will have to do it a polygon at a time, selecting each edge that you encounter on the way.

Figure 3.3. Adding the sternocleidomastoid muscles


You don't have to always end up in the corner of two edges; you can cut anywhere along an edge. However, it's wise to begin where a vertex already exists and try to end on one, too.


As you are cutting, you will find that occasionally you can't go any farther with the current cut. This could be caused by an unshared edge, or faces that are flipped the wrong way. It isn't a problemjust press G to finalize the current cut; this will also restart the Split Polygon tool. Then start a new cut from where the previous one ended.

If you are using a mirrored instance, you will notice that the cuts you make on one side will be mirrored across to the other. Also, when you create a cut, it automatically turns the new edge into a crease, making the normals hard. It's probably a good idea to smooth them as you go along. To do this, select the edges you wish to smooth. Then go to Edit Polygons > Normals > Soften/Harden and set the options to All Soft. Click the Apply button and close the options.

I think that's about all for the neck. As mentioned earlier, we only need a basic layout of the muscles. Adding too much detail now would be pointless because most of it will be removed later, when we optimize the geometry.


Moving down, we come to the upper body, so let's implement the collarbones next (Figure 3.4, left).

Figure 3.4. Adding the collarbones to the mesh

Use the Split Polygon tool to carve out the details, as shown in Figure 3.4 on the right. Don't be afraid to move some of the vertices to further sculpt the area until it resembles its anatomical reference.

If at any point you end up with tiny triangles starting to appear, as in Figure 3.5 (left), feel free to remove them. You can do this in one of two ways:

  • Right-click the mesh and select Vertex from the marking menu, moving you into vertex editing mode. Select the two vertices on either side of the edge you want to remove, and weld them.

  • Right-click the mesh and select Edge from the marking menu, moving you into edge editing mode. Select the edge you want to remove (the middle view in Figure 3.5), and then go to Edit Polygons > Collapse. This removes the edge, bringing in the vertices on either side and welding them (Figure 3.5, right).

Figure 3.5. Remove any tiny triangles by using the Collapse tool.

The Chest and Shoulders

Moving on, we can start working on the chest and shoulder area. Refer to the muscle reference in Figure 3.6, which focuses on the shoulder area. You can see that the huge muscle on the chest, the pectoralis major, stretches across and under the shoulder muscle, the deltoid. It would probably make sense to try and sculpt these at the same time, and then work on the armpit area before progressing to the rear of the upper body section.

Figure 3.6. Upper body muscle lines, with the arm raised

Using the Split Polygon tool, create a new line following the outline of the two muscles lying across the chest and over the arm (Figure 3.7, middle).

Figure 3.7. Add detail to the chest, shoulder, and armpit areas.


When you're done with an area, feel free to work on it further, adding more edges and manipulating the vertices until you are happy with the shape.

Looking at Figure 3.8 (left), the shoulder seems a little angular; this is because there are too few polygons here at the moment. When this area bends in animation, we will get quite a rough-looking deformation. You can prevent this by adding extra strips across the top as you continue adding the muscle lines.

Figure 3.8. Insert more polygons into the shoulder.

Split the polygons as I have in Figure 3.8 (middle), following them around to the back of the shoulder (Figure 3.8, right) while continuing the line for the deltoid muscle.

Move the newly created shoulder vertices out slightly to round off the area.

The Back

This brings us nicely around to the rear of the upper body. We don't need immense detail here, either, but it's important to get the basic muscles in.

Starting at the top of the back and moving downward, work in the trapezius, lattimus dorsi, and thoracolumbar fascia muscles (refer again to the anatomical reference as you go). See the left and middle views of Figure 3.9.

Figure 3.9. Add muscle lines to Kila's back.

Halfway down the back, just above the hips, there is quite a large space. It will make life easier if we subdivide this area, allowing us to continue adding the back muscles (Figure 3.9, right). Follow the cut all the way around to the front of the mesh.

Still on her back, we could implement the spine at this point. This will be a simple recess down the center of her back. First, though, as you can see in Figure 3.10 (left), there is another large area in between her shoulder blades. Take a moment to split this area, taking the cut across the center as in Figure 3.10 (right).

Figure 3.10. Subdivide the large polygon at the top of the back.

Now, to create the recess for the spine (Figure 3.11), split the polygons just on either side of the center, remembering to remove any small triangles that are created. Finally, move the vertices that run down the center slightly inward.

Figure 3.11. Insert the recess for the spine.

Now is probably a good time to delete that history that has steadily been building up.

The Stomach

Moving around to Kila's front in Figure 3.12 (left), we can begin to work in her stomach muscles. Split polygons and move vertices to get the general shape seen in Figure 3.12 (right).

Figure 3.12. Add muscle detail to the stomach.


It's important to remember that when you split polygons, Maya places the cut on top of the current polygons. This means that although you have divided the polygon, it will still appear flat when viewed from an angle. In most cases, as occurred with the stomach muscles, you will need to pull these new vertices out slightly to round the area off.

The Pelvis

Moving farther down the front of the model's body brings us to the next part to work on: the pelvic area. Because Kila is wearing jeans, there is not much point in mapping the muscles here, but we do need to make sure the area has clarity and deforms correctly.

Switch to the front view and make sure your image plane is visible. What you need to do first is mark out the top of her jeans. Judging by Figure 3.13 (left), we are in a good position. The edges at either side already lie in the correct position for the hip-hugging jeans; even the edges at the rear follow where her jeans should go, so you only need to fix the front. Go ahead and split the polygons at the front of the mesh, following the top of her jeans (Figure 3.13, right).

Figure 3.13. Create the area at the top of the jeans.

Now you need to address the groin area. The polyons seem to have moved down slightly so they no longer line up with the reference image. Also, the creases where the upper legs meet the hips need to be realigned. We want to end up with the mesh closely resembling the image plane, as in Figure 3.14. Don't worry if both sides don't match exactly; as long as one side matches the guide images, we are fine.

Figure 3.14. Fix the crotch area; position the vertices to match the guide image.

First move the vertices apart, creating a gap (Figure 3.15, left), and then use the Edit Polygon > Extrude Edge and Polygon > Append To Polygon tools to fill the hole. Afterward, work the vertices to round off the area, which should give you a nice, clean result like that shown on the right in Figure 3.15.

Figure 3.15. Fill in the gap, creating the crotch area.

What you can start to do at this stage is include creases in your geometry. Look at Figure 3.16 (left); this is how the mesh looks now, with all the normals smooth, giving us a nice smooth surface.

Figure 3.16. Add creases to your geometry by creating hard edges.

Figure 3.16 (right) is the same meshbut here there are creases added around the crotch, the upper part of the jeans, and under her chest. These creases are simple to do; it's just a matter of making the edges hard. Here are the steps:


Right-click the mesh and select Edge from the marking menu.


Select the edges you wish to crease, in this case under her chest and around the folds in her jeans.


Go to Edit Polygons > Normals > Soften/Harden and open up the options.


Earlier, we clicked All Soft to smooth out the geometry. This time, select All Hard. Then click Apply and close the options.

This isn't a vital part of the procedure; it just makes the geometry look better as you are working on it. To add balance to the model, as you would with a painting, you should have both hard and soft lines (edges).

The Buttocks

Time to work on Kila's rear. At the moment it's not much to look at (Figure 3.17, left), but we will soon fix that. As you did for the front, move the vertices to lie roughly where the creases should be, as shown in Figure 3.17 (middle).

Figure 3.17. Move the vertices to tidy up her bum.

You are now left with a huge flat area; subdivide that by splitting the polygons, as shown in Figure 3.17 (right). This still leaves the area flat, so switch to the side view and use your guide to round it off (Figure 3.18).

Figure 3.18. Round off the flat surfaces.

Rotate the model, tweaking the vertices until you are happy with the shape of the buttocks. Switch to the perspective view and look down on it from above to make sure she is nicely roundedremember to always refer back to your anatomical reference material.

You will probably notice that from certain angles she still seems quite flat. You can fix this by subdividing the long faces at the rear by creating vertical cuts (Figure 3.19, right). Before you do this, however, delete the edges designated in the left pane of Figure 3.19. Then add a cut at either side of the crease under the buttocks (Figure 3.19, middle).

Figure 3.19. Subdivide the long faces to smooth out the buttocks.

Continue tweaking, making sure you use your guide images. Figure 3.20 illustrates another area that could benefit from a little subdivision, smoothing it out and rounding it off. Here again, you'll split the polygons horizontally to subdivide the area; in fact, you can split these all the way around, ending at the crotch (Figure 3.20, middle). When you're done, tweak the vertices until the shape is just right (Figure 3.20, right).

Figure 3.20. Further subdivision is needed.

Figure 3.21 shows the entire torso with all its refinements. We have added geometry not only to help the shape, but also to aid deformation.

Figure 3.21. The refined torso

The Arms

The torso is more or less complete now. It has more detail, and the shape is coming along nicely. The next stage is to refine the limbs, starting with the arms.

To begin, we will build in a simple elbow. I have highlighted an edge in Figure 3.22 (left); this is where our elbow will be. All we need to do is pull that edge out slightly, but first we need to create four cuts (Figure 3.22, middle). As shown in Figure 3.22 (right), this will allow us to pull out the center edge, creating the basic elbow.

Figure 3.22. Build in the basic elbow.

Having the elbow in place helps us to complete the rest of the arm. Let's work on the upper arm first, sculpting in the biceps and triceps. Most of the arm detail can be achieved by simply moving the vertices. And rememberwe still need to refer to our muscle reference to get it right.

Begin to mark in the biceps by cutting the polygons to create the outline; Figure 3.23 (middle) shows these cuts.

Figure 3.23. Carve the biceps into the mesh.

Now work on molding the biceps into its correct shape. If you are at all unsure about how it should look, use a good arm reference to get it looking right. Figure 3.24 shows the finished biceps on our model.

Figure 3.24. Manipulate the vertices to get the biceps correctly shaped.

Moving around to the back of the arm (Figure 3.25, left), we can work in the triceps. First cut in the outline shown in Figure 3.25 (right), and then move the vertices to achieve the desired shape.

Figure 3.25. Create the triceps.

You may not need to cut any polygons for the forearm; just make sure the shape is correct. The muscles run down toward the wrist, as our edges do anyway, so it would be a waste of time to work in every muscle; further detail in this area can be gained by her texture.

We now have enough definition in the upper body. You can, if you like, spend a bit more time mapping in the rest of the muscles, as I have in Figure 3.26. Round off this section by doing what makes up 90 percent of most modeling: rotating and tweaking. Move around the model and make sure it is smooth, anatomically correct, and clean.

Figure 3.26. Upper body muscle maps

When you're done, delete the history and save your work as Kila_Muscles.mb.