Level of Detail Weights

We have worked hard to tweak the weights on the first LOD until Kila deforms accurately as she moves. Now we need to apply the same weighting values to the other four levels of detail. This does seem like a huge task, but luckily Maya has a handy toolCopy Skin Weightsthat lets us copy the weights from the first LOD across to the others.

We first need to prepare the geometry as we did for the main model. Select the LOD group in the Outliner, and make sure all the layers are visible and that each LOD is set to "show" in the Channel Box (Figure 14.45).

1.	At present, your Outliner should look like the one in Figure 14.46, left. Go through each individual LOD and combine the geometry into a single mesh (Polygon > Combine), remembering to merge the vertices around her hair with a small value of 0.001. Figure 14.46. Combine each LOD into a single mesh. NOTE If you are using the blend-shapes version, remember to keep the faces separate wherever blend shapes have been applied.
2.	Place the models back inside their LOD group. Delete the history and rename them to Kila_LOD02, Kila_LOD03, Kila_LOD04, and Kila_LOD05 (Figure 14.46, right).
3.	When copying weights, the number of joints to which the source and destination mesh are attached has to be the same. Therefore, you have to be sure each LOD model is bound to the base skeleton in exactly the same way as the original. A quick way to do this is to select each new LOD model in turn and click on the Bind button on the GCDM shelf. This will ensure each level is bound to the base skeleton just the same way as the original. With all the geometry attached to the skeleton now, we can copy the weights across. We simply tell Maya which mesh we are copying from, and which we will be copying to.
4.	Select the first LOD that you have already weighted, Kila_LOD01. Now, holding Ctrl, select the next LOD (Kila_LOD02).
5.	Go to Skin > Edit Smooth Skin > Copy Skin Weights.
6.	Repeat steps 4 and 5 for the other LODs, selecting first the main LOD (Kila_LOD01) and then the one you wish to copy the weights to.

Figure 14.45. Make each LOD visible by setting them to "show."

All the LODs now have the same weighting applied to them, so they will deform nearly the same as the first LOD does. This also means that the facial animation setup for the joint facial rig is carried across to the second LOD, saving us from having to set it up again.

Now go through each LOD and check that the weighting is correct on each model. Due to the change in topology, there will be areas where the weighting has accidentally affected some vertices incorrectly. This shouldn't take much work; the majority of the weighting will have passed across just fine.

TIP

Remember that these are LODstry to view them from the same distance at which they will ultimately be viewed in game. There is no point in spending time adjusting weights on areas that will never be seen.

When you are completely happy with the weighting on each level, set the Display Level on each LOD group back to "uselod," and make all the display layers visible.

As demonstrated in Figure 14.47, all versions of Kila are now weighted and checked, allowing us complete freedom to put her into any pose. Save this version of Kila as Kila_Skinned.mb.

Figure 14.47. Kila, fully weighted