Corrective Blendshapes

[Anonymous No.918480]

So after learning and studying rigging and skin weights, testing dozens of models and creating my own character, I found out this is not really enough.
Im using Maya and saw many of the most complex models out there use corrective blendshapes.
Is there any specific tutorial for these? Critical areas like knees, elbows, the waist area and similar poses.

I tried creating a blendshape, assign that one to a control (elbow) and activate when it reaches a certain angle. But that doesnt really work out at all.

>Is this necessary? How -should- it be done? Which is the correct way?

[Anonymous No.918492]

>>918480
>Is this necessary
Depends on the model and usage.
In low poly i've seen that you could just weight it properly and it will look passable.
If the model is going to move really fast or/and at a big distance from the camera, or other reasons you won't notice it, it'll bee overkill and unnecessary .
>Which is the correct way?
The one that gets the job done. The most common one seems to be bone-driven blendshapes.

[Anonymous No.918498]

>>918480
dont use correctives, use an underlying muscle system such as ZIVA (even used on multi platform multimillion selling hit SPIDERMAN)

[Anonymous No.918549]

Its a pretty standard approach at least in feature film rigging. I'm not sure the best way with vanilla software but you basically have the right idea. If you can find a pose system (like psd, rbf or sdk) to drive the shape that'll probably help a lot. I don't know how you're extracting the angle, but how you do that pose space reader is the key. Its also useful to control the blend in of the shape and be able to mix multiple angles/poses together.

[Anonymous No.918552]

>>918549
films do not use blendshape other than for the face, they use either in house muscle simulation systems, houdini muscle, or ZIVA (maya)

[Anonymous No.918556]

>>918480
>Which is the correct way
7/10 the problem is the topology. Edgeloops tend to collapse around itself. Using references and placing them around muscle groups will get the result that you're looking for. Corrective Blendshapes are more of a last resort if you want more accuracy.
https://www.youtube.com/watch?v=scGF8IlsCsI

[Anonymous No.918587]

How about gaming industry? Surely there they use corrective blendshapes and morphs? Or do game engines recognize muscle systems from maya?

[Anonymous No.918589]

>>918587
>Or do game engines recognize muscle systems from maya?
have you played SPIDERMAN?

[Anonymous No.918590]

>>918587
I think games use baked animations instead of live rigs.

[Anonymous No.918592]

>>918587
I use Unreal Engine after doing all the animations in Maya and yes, I bake all the animations into different fbx files.
Then theres the main skeleton file which has all the blendshapes.

[Anonymous No.918593]

>>918480

I am now two days in trying to figure out how I can make shape keyframes act like a regular action, so I can export that shit to Unity properly. Does anyone know?

[Anonymous No.918656]

>>918593
Dont drive it with a controller (directly key on the shape key itself) and it should export with no issues. If you already did that, heres a script: https://blender.stackexchange.com/questions/105914/broken-script-to-bake-keyframes-from-driver-controlled-shape-keys/106370#106370
>>918480
>is it necessary
No just paint your weights better lmao dont be lazy

[Anonymous No.918667]

How do I do this in blender so it works in godot?

[Anonymous No.919411]

>>918556
that topology didn't help the knees or elbows at all

[Anonymous No.919413]

>>918480
All standard rigging (like what you see in video games or some movies) is completely flawed from an anatomical perspective. Blendshapes are a way to polish a turd so to speak, you're fixing the mistakes that pop up when using a flawed approach.

There is no real rule for blendshapes other than "make it look good" and in order to make it look good you need to know how it should look in the first place and in order to know how it should look you need to have an in-depth knowledge of anatomy.

[Anonymous No.919430]

>>918480
You are making a rookie mistake that is to consider human bone structure same as rig.

Don't do that.

Human body has gliding objects, has stretching, bulging and all that bio shit that people simulate nowdays for big movie productions.

What you need to consider is topology and bone placement.

Like the image aboe, i can only imagine that You didn't do the knee joints breakaways, and indeed you probably moved the middle of the joint too close to the kneecap, away from the bending point.

Blendshapes arent supposed to fix Your mistake fully. They are just there for minor tweaks mostly.

[Anonymous No.919438]

>>919430
>You are making a rookie mistake that is to consider human bone structure same as rig.
>Don't do that.

Worst advice you will ever get in your life, OP.

[Anonymous No.919445]

>>919438
too bad there is no ID in this forum, because i would know which post i need to ignore.

[Anonymous No.919449]

>>918480
Import it to blender it have a better rig system and is free.

[Anonymous No.919457]

>>919449
>Blender
>better rigging system
top kek

[Anonymous No.920540]

>>918480
to fix the knee, just add an extra small bone at the knee point! bones are physical objects rolling off each other and literal point rotation will only force the leg mesh to intersect with itself. do this and with some balanced skinning, you will be able to bend the leg and dig the heel into the butt like real humans can do when sitting on the legs- no shape correction required! the hips are another issue for me- again, added a small route bone inside the hip as the thigh bone is shaped like a golf club thus its rotation is also offset! this more or less enabled me to do the splits and kick and draw the legs in with little need of correction. didn't feel the need to do this for elbows as they actually do bend closer to literal point rotation and are naturally limited in bend due to the muscle bulge. as for the waist, you want the route to be at the top of the hip so you can hip thrust without affecting the mostly bottom to top flow of the rest of the spine to the head! i use position and rotation and stretch-to constraints to do those!

[Anonymous No.920654]

>>920540
If I modify the unreal skeleton to include for example that extra knee bone. Could I still use animations built for the original skeletons or would I have to retarget the animations?

[Anonymous No.920808]

>>918667
Godot doesn't know about Blender.
Export from Blender to FBX, import FBX in Godot.

So first find out how to get your shapekeys and their strength keyframes into an FBX file.

[Anonymous No.920809]

>>920808
...actually, RTFM and use the format that they recommend in there, which is not FBX:
https://docs.godotengine.org/en/stable/tutorials/assets_pipeline/importing_scenes.html#godot-scene-importer

[Anonymous No.921491]

>>920654
i'm only playing in blender right now but i would do this for any softwhere- i didnt see a dramatic change in how my legs worked with the ik set up, as its the anckle target you use to grab and lift the leg about and didn't do anything bad- i added the extra bone after i had made my rig and troubleshooting how to stop the leg crushing. its not meant to be percievable as an actual extra bone so probably wont hurt unless bones are being counted so that that extra knee bone is percieved to be the shin bone or something like that (i can only guess)

[Anonymous No.921504]

corrective blend shapes are the solution which will work 100% of the time in all cases and look 100% perfect. Because you will need to make the perfect blendshape for every single use case. Every other solution is primarily designed to avoid that work, but will always have some limitation which can only be cured with, you guessed it, a blend shape.
In pic related I have this giant ass which loses a ton of volume. I have added an intermediate joint between the hip and the femur which bares some of the influence on the butt. It's reduced the reduction in volume by like 75%. If I wanted it better I could add more intermediary joints and I'll be experimenting with "flying joints" which will sit close to where the geometry actually is to save volume, but it will never work 100% and there are orientations where the solution doesnt work at all. It'll be a decision I make if I do blend shapes, blend shapes + some alternative, or some alternative + just accepting it'll look bad sometimes.

[Anonymous No.921591]

>>921504
Good stuff. Plus the drawback of blendshapes is you need to replicate them on additional meshes such as clothing for the character and depending on the complexity of those items that is going to be a bigger challenge.
Because of that I also chose the helper joint approach. There is 3 different extra bone systems working here to produce this result. You can see it isnt perfect either but it looks ok and does the job to preserve volume in various poses.
The upside is that I can get 90% of the transfer work done with 1 button by just copying skinweights over.

[Anonymous No.921594]

>>918480
Made a tutorial for something like this, different area same workflow tho. Maybe you can get something out of it: https://www.youtube.com/watch?v=djOQItZfno4

[Anonymous No.921595]

>>921591
https://www.youtube.com/watch?v=ViIvQWLm9rQ&ab_channel=Faux2D

zero blendshapes, bro

[Anonymous No.921598]

>>921595
no wonder it looks like shit.

[Anonymous No.921600]

>>921595
>daz
bro

[Anonymous No.921603]

>>921594
Thems really good shoulders. Thanks for sharing info :)

[Anonymous No.921615]

>>921594
I prefer this video here:
https://www.youtube.com/watch?v=vEhHRU7f_Mo

[Anonymous No.921623]

>>921598
ngmi
you hate to see it T _ T

[Anonymous No.921675]

>>921591
>>921594
So you made these WITHOUT corrective blendshapes? Why did you link to a video about doing corrective shapes?

[Anonymous No.921677]

>>921675
Maybe because that was OPs original question?

[Anonymous No.921678]

>>921615
The other one is more up to date with the blendshape generation tools. It uses a maya native command instead of some random script you need to download and it shows you a proper method to connect the blendshape to the rig instead of just lazily hand-keying the blendshape.

[Anonymous No.921690]

>>921504
your mom bares some influence of the butt

[Anonymous No.921696]

>>918587
corrective code driven joints is the most common solution
blendshapes are used mainly for expressions phonemes etc(i.e. all things facial)

[Anonymous No.921697]

>>921696
>Mainly for expression phonemes

Take so retarded it brought down further the overall IQ of this board by couple of points.

[Anonymous No.921752]

>>918480
Gonna be honest anon, stop being autistic about weight paint, there is no such thing as a perfect rig and if there was they are not paying enough, good enough is fine and weird body movements even happens in AAA games,if you want tip, if your joints look fugly, select the nearest bone and apply .2 in the weight paint, it will fix most things

[Anonymous No.921813]

>>921591
Looks a 100 times better than loli pop chainsaw which had every reason in the world to not make their character's ass collapse when she bends over.