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stelovcgi
07-07-2005, 03:37 PM
Hi,
Can anybody help me with a good way to make corrective blendshapes please?

I'm struggling and I've tried several different techniques to no avail - so please if anyone could help me with a walkthrough technique I would be SO grateful.

I really wanted to use something like this technique from Morganism in a previous thread ....


" I'm not sure about the best way, but I've tried it a couple different ways. I think the easiest way is to bend the elbow, (for example) and then duplicate that mesh with the bent elbow twice. On one of the duplicates you move points around until everything looks peachy. So you've got your character with the rig and everything, a mesh that has an unchanged bent joint, and a mesh that has a corrected shape. So you take those two meshes and add them to your skinned character as a blend shape (make sure the blendshape comes before the skin cluster). Then you put the corrective shape to 1, which will double transform your arm, and so to fix that you set that other mesh to -1. That will subtract the arm bend and leave you with just the verts you changed for the corrective shape. Then you bend the arm back to the bind pose on your skinned character, duplicate the mesh, and that gives you your corrective shape. You can delete everything else. ".....


......this seems ideal but I can't get it to work - even on a simple poly-cylinder experiment. When I add the blendshapes, the corrective one doesn't cause a double transform, and setting the second mesh blend slider to -1 doesn't subtract the 'bend'. I just get a mess.
Are my settings wrong? ( blendnode above skin cluster in 'all inputs' on the character and blendshapes added separately at default settings). I did download BSpiritCorrectiveShape.mel, but I am bewildered as to how it works?

appreciate your help, sorry if this is all basic stuff - I'm pretty slow......

Kriz
07-07-2005, 06:45 PM
Have you tried to use influence objects. I find those easier to use than blendshapes for elbows and such.

michaelcomet
07-07-2005, 07:55 PM
Your best bet is to do the sculpt in the base pose so there is only one shape and no subtraction needed.

Or else use my free Pose Space Deformer plugin avilable on my website...

-comet

FiendishVegan
07-07-2005, 08:45 PM
Okay lets say we're trying to fix a bent elbow area

1. duplicate the bent arm twice

2. Sculpt the fixes you want on one but not the other

3. Select the negative shape first, then the corrective shape, and add them to the rigged arm as blendshapes using a parallel blender.

4. Set the negative shape to -1 and the corrective to 1.

5. Set the rigged arm back to a straight(not bent) neutral pose.

6. Duplicate this new mesh.

7. Delete the blenshape node from the rigged arm and delete first two corrective shapes.

8. add the new straightened shape to the rig as a blendshape.


Hope that helps you...good luck.

stelovcgi
07-07-2005, 09:37 PM
Thankyou SO much, really quick replies. The Parallel blend technique was exactly what I was looking for - but thanks to Kriz and Michaelcomet for your advice too! so kind...

grrinc
07-07-2005, 11:03 PM
Okay lets say we're trying to fix a bent elbow area

1. duplicate the bent arm twice

2. Sculpt the fixes you want on one but not the other

3. Select the negative shape first, then the corrective shape, and add them to the rigged arm as blendshapes using a parallel blender.

4. Set the negative shape to -1 and the corrective to 1.

5. Set the rigged arm back to a straight(not bent) neutral pose.

6. Duplicate this new mesh.

7. Delete the blenshape node from the rigged arm and delete first two corrective shapes.

8. add the new straightened shape to the rig as a blendshape.


Hope that helps you...good luck.

Could I ask what are the benefits of doing this way?? I am a noob to the rigging side of things and this seems such a long winded way of doing each Blendshape. I kinda liked Mike Comets answer!! ( by the way Mike, I have dabbled with your free pose deformer and i liked it very much - the trouble is cMuscle has distracted me!! i will be purchasing very soon when the missus gives me the nod ). Many thanks.

michaelcomet
07-07-2005, 11:14 PM
Thanks for the comments.

Yeah I'd kind of agree, this seems to be more of the "do by hand approach". Although sometimes I guess there may be times when you want to get a clean blendshape out and just use a blendshape node... I've been using my PSD in production for a while now and I know other studios have used it as well.

-comet

M.E.L.
07-08-2005, 01:19 AM
Or else use my free Pose Space Deformer plugin avilable on my website...

-comet

quoted for agreement. your best bet is right there :)

-s

FiendishVegan
07-08-2005, 02:11 AM
The method I described earlier is the best way I've found to subtract out negative blendshapes. Creating corrective blendshapes in the base pose seems like modeling half blind in my opinion. The benefit of subtracting is you can sculpt on a posed shape and see (more or less) exactly what your final results will be as you model the shape.

And while I'd love to take credit for this technique, I picked it up from Paul Thuriot.

michaelcomet
07-08-2005, 02:42 PM
I think we all agree sculpting in base pose "blind" as you say is definitely not good.

My point was only that the PSD plugin lets you sculpt normally like you are talking about, but also has the benefit of setting up the angle or translation triggers and blending of the shapes as well with the complete deformer and utility nodes. That's all.

-comet

M.E.L.
07-08-2005, 06:04 PM
As Michael has stated, for the sake of simplicity and ease of use the PSD solution is your best bet. You gotta remember that with 'corrective shaping' you are going to constantly be fighting against additive shapes, struggling with the skinCluster and the worst issue being exploding verts when multiple shapes are being driven off a joints rotation. Pile this on with the risk of getting into serious gimbal lock on ball & socket joints when driving corrective shapes and the PSD solution really begins to shine.

PSD's are just a much cleaner, organized and nicer approach to what you are looking to achieve. Save yourself the headaches, go get Michael's tool :thumbsup:

-s

brook kievit
07-08-2005, 07:00 PM
you can also try http://www.b-ling.com/ its very fast. more accurate then the pos neg trick.

stelovcgi
07-08-2005, 07:01 PM
O.K., you swung me round to your way of thinking.

Having read M.E.L.'s comments and the full descriptions of what the PSD plugin does, I'm totally won over ( although slightly bemused that Alias haven't integrated something like this into Maya themselves ).

Just out of interest ... are there any drawbacks to using PSD? it seems ideal; I'm suprised it isn't more famous - or maybe everybody knew except me.

Thankyou all again,

Stephen

M.E.L.
07-08-2005, 11:00 PM
O.K., you swung me round to your way of thinking.

Having read M.E.L.'s comments and the full descriptions of what the PSD plugin does, I'm totally won over ( although slightly bemused that Alias haven't integrated something like this into Maya themselves ).

Just out of interest ... are there any drawbacks to using PSD? it seems ideal; I'm suprised it isn't more famous - or maybe everybody knew except me.

Thankyou all again,

Stephen




Only drawbacks are that it can be a bit computationally intensive when first creating the poses and stuff on heavy meshes. After that it's pretty straightforward and simple, Michael has even included the ability to 'prune' out any unaffected verts to speed up computation during playblasts etc.

-s

michaelcomet
07-09-2005, 12:09 AM
Actually you can also prune/edit membership ahead of time as well, which greatly speeds up calc of the target when setting it up. ie: if you are setting a PSD for the lower arm only, editing membership on that FIRST will greatly speed up the processing calc since it will only look at points in the membership when creatign the internal data target.

M.E.L.
07-09-2005, 12:56 AM
Well.... that sure felt like a swift boot upside the head!

Thanks Michael, I didn't know you could edit out the unaffected verts beforehand!

-s

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