#SL Mesh Deformer Discussion

There is some discussion going on in the JIRA thread STORM-1716. Everyone should be able to see the item. I am not sure who can and cannot comment on it. The comments over the last week or two are on the current Deformer, which I call 0.4.

Problem with Default Sit Pose

User Error

One of the Deformer problems Karl described as User Error. That term is going to mean different things to different people. I think Kitsune Shan best described the problem saying, “Anyway, I see why Qarl says that about “user error”. Most people here use Blender, they trend to just select the mesh and the skeleton, so the weights are copied, but NOT correctly applied. Handmade weights are always necessary if you want to do a good job. And the other factor is that people keep paying more attention in how the default mesh deforms than using a custom one. Tests can be done using a very high poly density mesh, so changes, spikes and vertex problems are more visible. Using the default avatar shape isn’t too bad as “test” but remember, no one will use the default mesh to make clothes.

I tend to believe and agree that significant number of people are using Blender and the weights copy without spending time adjusting the weights. Not all, but a significant number. If you use the system sit pose that swings the right foot to the left, you can see most skits have the same odd bump in the skirt center. This very common in any skirt made with simple weight copy. I think this simple build process is a good part of what is being called User Error.

I disagree that people are not going to use the default avatar and even more so with the idea they should use a custom avatar. I think using any shape other than the default avatar is another part of the User Error. Remember. The Deformer calculates offsets from your designed mesh attachment to the default shape. It then applies those offsets to your mesh from the current shape your avatar is wearing. I know that can be confusing. Take away from that statement that if you use a base shape other than the default one for your design and feed it to the Deformer, you will likely get odd results.

I discuss the default shape and avatar in: Second Life Mesh Clothes Blender 2.6 Setup 2012 Tutorial. Scroll down the page to see the index of what is discussed on which page.

The default shape is the one you get when you start to create a new shape from scratch in the Appearance Editor (Gear Icon – New Shape). The default shape uses a set of default slider positions with the SL Avatar mesh. Karl has based his Deformer on that shape and those settings. Using any other shape and then basing the deformation on the default just isn’t going to work well.

I suspect that is a common user mistake, error.

Real Bug

There is a real bug in this version of the Deformer. BUG-157 – Interaction between graphic shader setting and deformation enabled mesh. You see this bug when wearing deform-enabled mesh created to the base avatar. It fits said avatar as intended when the shaders (Skinning) option is enabled. But when the shaders (Skinning) option is disabled worn mesh shrinks in size rendering the mesh inside the avatars body. (The enabled/disabled seems reversed here… I’ll have test it to see which is right.)

I ran into this problem earlier without realizing what was happening. Karl says this problem has a simple fix that has to do with some switching in the render pipeline based on shaders. So, I expect it to get cleared up easily if not quickly.

2 thoughts on “#SL Mesh Deformer Discussion

  1. Yeah, I been saying for almost a year now that creators have to tweak the weights. I know that it can be a huge pain in the butt, but it must be done to get good results. I’ve not made much clothing, but I did make my own mesh avatar. Basically, I must’ve redid the weights on my mesh avatar about 20 or more times. Once you have a good set of weights, you can drop those weights onto many of your clothing items with minimal reweighting. You can’t just use the default weights and think that is going to work on everything, especially uniquely stretching outfits.

    It’s also probably a good idea to add some verts in areas that will stretch the most. This will also help with the textures stretching too much in those areas. If I were LL, I would give a suggested total vert counts for clothing, as so many people have no idea what is reasonable.

    Although I was totally against Standard Sizing, I do like that Karl added in the ability to use a custom shape. I said from the beginning of the Standard Sizing fight, that the real solution was adding custom shapes. This could make it possible for most clothing to fit most sizes, even custom mesh avatars, as long as the custom shape is not imbedded in the mesh clothing.

    What would be super cool to see happen, would be for Blender to automatically reshape mesh clothing to whatever shape avatar you are using. I could very much see people asking for custom fit clothing, but I don’t see this as a viable option unless it is super easy for a creator to do quickly.

  2. Adding my agreement to the necessity to learn weight painting and make manual tweaks, or weight completely from scratch. Not only does copying the weights from the default avatar not usually give the most satisfactory results, but the Blender files most of us have aren’t actually 100% accurate when it comes to the weights on the avatar in world. (I use the fine ones provided by Gaia Clary on the Machinimatrix site.) These inaccuracies only get exaggerated further doing a bone weight copy.

    This is actually not too difficult to see if one imports the vanilla avatar from the one of these files in world in certain poses. For example, a person might put the avatar into a simple sitting pose, with the knees raised and level to the hips, and take a look at the buttocks. You can see that one of the buttocks is strangely flattened, while the other stays rounded. It’s probably only a single vertex that’s not weighted quite right, but it makes a noticeable difference.

    So further refinements to the files we use as a base might also help reduce cases of user error, although that’s not a substitute for doing the hard work yourself.

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