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Voxel model for animation/games: Questions about joints / blendshapes / neutral pose


Gian-Reto
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So after years of concentrating on hardsurface / vehicle sculpting to get around the need for rigging, I finally decided it would be time for me to try again and create an organic character for animation.

 

I have done that 3 years ago and friends rigged the character, but the result was not so convincing. We all did a lot of newbie mistakes. I took a break from organic characters for some time because of that also.

 

This time I want to get a better deforming mesh, and a better rig, so I decided before I dive into creating the high poly details for my current project, I would step back and think about how the mesh would deform during animation, so that I didn't had to go back and rework my detail mesh after I found the errors later during rigging.

 

While I know about the importance of a good edge flow, and there is plenty of information about that floating around the internet. When starting to research into how to create advanced rigs, several questions came up, as well as questions raised myself when starting to get into the high poly details.

 

 

Be aware that I intend to use Blender for rigging, and animating the model. While I hear that Maya has a pretty good animation workflow, I wasn't to fussed about my general productivity in Maya when I gave it a spin for some months last year. I also would only be able to afford Maya LT, which seems to be more limited.

So for now, I'd like to go with the free alternative that seems pretty usable after "trying the grass on the other side" :)

 

 

1) Clothing Joint details: in other words, the folds of clothing around joints... should they be completly omited so that you don't get problems when the polygons around the joint stretch or compress during movement of the bones?

 

If (and I am not sure here I need this layer of detailing in my use case) I want the clothing to fold and wrinkle during compression, can a blendshape do this? Or is the Blendshape better for lower frequency changes like general flattening of the lower leg muscle during compression of the knee? Is the only way to achieve that what is known as "stress map" (wrinkle map?)? What is the best way to generate such a "stress map" (altough I am not sure that I could use it, have to see if somebody got it work with UE4)?

 

When designing realistic models for "lower detail use cases" (for example where the camera is not getting close to the character), do you generally just try to get a more or less convincing shape fitting quite tightly around the joint so that you don't have to worry too much about the change in shape the clothing goes through during deformation?

Do you even artificially "round" the gaps between the body and the arms, or the legs so you don't get normal map errors when the geometry there gets stretched during animations?

 

 

2) Shoulder joint / T-Pose vs neutral pose: I get that the T-Pose is no longer the one Pose to rule them all even for rigging. And given that my character wouldn't lift her arm over the 90° angle very often (should wield pistols and a knife, no swords or similar weapons that would need that movement), I guess I would want to go for a pose closer to a 45° angle in the arms for ease of sculpting and the least amount of stretching during normal movement. As the character wears a body armour, there is even some space to hide additional "shirt geometry" to limit the amount of stretching/compression needed under the arms.

 

Now, this character should be quite athletic, even though it wears armour over most of its joints, and the body armour will limit the movement of the shoulder in the up direction. So I would want to have the ability to raise the arms over 90° even though this will not be needed often.

 

What is the best way to tackle this without going with a t-pose and creating problems with lower arm positions? As said, I made some bad expieriences with sculpting in a t-pose, and what I read around the internet I am not the only one with such problems.

I have seen people use more complex dual joint setups for knee and elbow to get more convincing bending (Altough I am not sure this is a good idea if the rig should be used in games), is a similar setup advisable for the shoulder (as the arm itself actually does not raise over 90°, its the shoulder that does)?

 

Do most people bring their models into a neutral pose (with all joints bent halfways) before finishing the sculpt to reduce the amount of texture stretching?

 

 

3) Blend shapes: I get that to really get convincing deformations, blend shapes are a must. Now I am not that keen on changing the vertices of my exported 3D coat models around in Blender... I am pretty sure now with support for "custom normals" (how blender calls the vertex normals), that shouldn't be so much of a problem as before, but still, the thought makes me uncomfortable.

 

I guess resculpting in 3D Coat is no option though, as you would want to reuse the normal map and all.

 

How do people create their blend shapes if the model has been created and exported from 3D Coat? Just pull the vertices around in your 3D Package of choice?

 

 

4) Armour with semi rigid parts: The Body armour planned and partially sculpted for the character should be "semi rigid"... basically rigid cloth (like a kevlar vest) with additional armour plates attached. Now, because of that, I get plates that should be completly rigid, and attached cloth that should be rigid at where it attaches to the plate, and deform more the farther away from the plate.

 

What is the best setup for that? Plate as one mesh, the rigid "kevlar" part as another, and the rest of the character as the third? Only keep the plate separate, combine the plate and the kevlar cloth, or combine everything into a single mesh as weight painting alone could do the trick here given a good enough edge flow?

I have though about combining plate and kevlar parts of the body armour into one mesh, but keeping the body armour separate from the rest of the body so I can hide additional body geometry below the body armour that can help with stretching, while keeping the body armour looking more rigid as it would stretch less (as described above)... is that a good idea, or completly stupid?

 

 

Thanks in advance for any help... I am pretty lost on the whole rigging topic. And yes, I am pretty sure I am trying to run before I even can crawl here, and that I will fall flat on my face with this most probably.

 

Just trying to land a little bit softer, thats all ;)

Edited by Gian-Reto
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Many of your motions can be generated with morphing to accommodate closeups but save work where possible, Edge flow around shoulders, elbows,knees and hips should minimize stretching. 

 

Thanks for your quick response!

 

 

From googling I guess Morph Target = Blend Shape, correct?

 

Then I would guess the best way to create the Morph Targets would be to create a mesh from the voxel sculpt, and then deform this in the sculpt room, or an external application, correct? Or is there an efficient way to use the voxel or retopo room to create the morph targets?

 

I guess I should use morph targets to minimize problems arising from joints reaching their extreme positions... Question remaining there is what is the best way to keep the normal map "clean" in the areas that will be stretched so that there are no folds or similar things baked into the normal map during the retopo that will look off during posing later?

Do I just need to leave enough space between the body and arms or the legs (and thus maybe raise arms and legs a little bit) so that this can be achieved easier?

 

If you say edge flow should minimize stretching, do you mean INSTEAD of rearranging the joint to a mid position for retopo, or IN ADDITION to that?

How common is the practice actually to not use a normal t-pose anymore for retopo and baking to avoid issues during animation nowadays?

Edited by Gian-Reto
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You can minimize stretching by using loops that are close together where stretching is likely and wide apart where compressing occurs. In an elbow for instance, the loops above and below the joint would be closest on the 'backside' or bone side of the elbow and furthest apart on the 'front' of the elbow where the compression occurs. There is a 3DC to Lightwave morph target tutorial somewhere.

 

As for keeping the normal map "clean",  I would do what looks good and deal with issues like morphing in the App you use for animation.

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You can minimize stretching by using loops that are close together where stretching is likely and wide apart where compressing occurs. In an elbow for instance, the loops above and below the joint would be closest on the 'backside' or bone side of the elbow and furthest apart on the 'front' of the elbow where the compression occurs. There is a 3DC to Lightwave morph target tutorial somewhere.

 

As for keeping the normal map "clean",  I would do what looks good and deal with issues like morphing in the App you use for animation.

 

Ok.... I think I am mostly worried about texture stretching that occurs on the stretched side, but maybe I am too worried about that. What does seem to be a bigger problem though is getting a nice "neutral"  form that deforms well in all directions and has no normal map details like folds that interfere.

 

Let me visualize what I am worried about (see attachment)

 

Examples for areas of the body I am worried about. If I leave the model in its current pose, I will have a hard time preventing folds in this area, even if I resist the urge to add folds from the clothing. Even if I fill these folds with edge loops, These Polygons get quite rounded normal map values baked into them.

 

What happens with the normals from the normal map, when I will have to move the vertices a lot for the morph targets that should eridicate the folds for the stretched position in these areas?

Wouldn't it be better to go for the pose with the least amount of folding (which, in case of the knee, could mean a straight position), as adding folds with a morph target later is easier than erasing the normals from a fold in a morph target?

 

 

EDIT: Ah, just found a very interesting discussion on the UE4 Forum: https://forums.unrealengine.com/showthread.php?95514-Wrinkle-Maps-Tension-Maps-How-do-you-set-them-up-%28workflow-requirements%29

I guess having multiple normal maps that could be blended in depending on stretching or compression of a joint would tremendously help making the whole thing look more realistic.... general consensus seems that this should be calculated offline though... vertex colors maybe?

post-6386-0-99787200-1453963732_thumb.pn

Edited by Gian-Reto
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As a note to anyone coming to this Thread in the future looking for an answer to similar questions:

 

I have started to do an experimental rig with a test model I baked out in 3D Coat. I guess I should have done that from the start...

 

Seems I did worry too much about the normalmap being a problem. It seems to adjust just fine to the stretched and squashed geometry.

The folds in skin and clothing pose a problem as expected and should be avoided.

Edited by Gian-Reto
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Building your own rig? It has been awhile since I done any rigging learning. Your thread though is sparking my interest again. 

 

I found that getting the armatures rotation axis in relationship to each other is one of the fundamentals and mucho problems if not setup correctly. 

My 4 sec animation... LOL from over 2 years ago... Wow, been than long since I touched it... 

I baked a model from 3DC as you have done.

 
I have not bought this training video, was made the Blender 2.5xx  but according to the site is ok for the 2.7xx series of Blender. I listened to a few free tutorials by Lee and he does well in explaining stuff... He also has released the rigged model free without having to buy the video...

 

Edited by digman
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I am putting this information here for others, as they also might want to delve into the rigging and animation abyss.

David Ward... 

Johnny Blender 3 - Pt 13 - Building the Rig/Armature

He is a good teacher. 

For the complete series watch Part 13 to Part 22. Done with an older version of Blender but nearly all applies.

https://www.youtube.com/playlist?list=PL2ACD3BDD66D4DC4E

 

Edited by digman
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