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For future reference should I use a T pose, or an A pose for any of my current/future models? Because A poses are hard for modeling/rigging arms, especially the hands. But I've seen countless other movie studios and game developers using A poses and they seem fine, how do they do it?

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The main reason to prefer a T-pose is exactly what you've experienced: the arms are more or less aligned with world axes. For some styles of modelling, that can be easier. (But for a lot of styles of modelling, it doesn't matter whatsoever. If you sculpt and retopo, you're not modelling by extruding loops out in various axes. And even if you're box modelling, working at an angle to world axes becomes less trouble the more tools you learn and use.)

The main reason to prefer an A-pose is that any reasonable deformation to the model is closer to the rest model. Closing your arms is a 90 degree rotation from a T-pose, but only like 45 degrees from A pose. So your edges don't deform as much in A, your UV doesn't stretch as much, etc. In the extreme case of this, we could be imagining organic models where we wanted to allow plus or minus 180 degrees rotation, using volume preservation (quaternion skinning). You get terrifically ugly interpolation through the 180 degree mark, so you want that mark to be the least likely deformation you're going to see, and you choose your rest pose on that basis. (90 degrees, plus or minus, is also a place where you can see some problems with some rigging techniques, so if you can avoid that by pose choice, you do it.)

There are other elements to choosing poses. In Blender, the biggest is how IK behaves, where it is far simpler to pose a model with realistically bent joints if you want to use IK on those joints. You can work around that, but it's not as convenient.

You can go further with the A pose. You can rest model the legs spread, duck feet, knees more bent, clavicles aimed slightly toward the sky... All of that places your rest pose more squarely in the middle of likely deformations. The reason to avoid doing all that is because you might find it difficult at that point to understand your character and their proportions.

Note that there are plenty of modelling techniques that will let you change rest poses. At the absolute minimum, you can apply an armature modifier! Hands are often modeled separately, then rotated and joined to arms.

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  • $\begingroup$ I see so to sum up, start with T-pose when modeling, then use A-pose to pose the model when I rig it with armature to see if the joints are acting properly. Am I correct or did I miss read it? Also any other tips? $\endgroup$
    – Stephen
    Nov 3, 2021 at 14:44
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    $\begingroup$ I would only add that as a compromise, most rig generators for Blender tend to use a modified T-pose where the limbs are bent slightly to accommodate IK requirements, and many 3rd party apps to generate characters do the same thing. See rigify as a built-in example. $\endgroup$ Nov 3, 2021 at 14:46
  • $\begingroup$ If I may also give my 2 cents: If you are animating a fairly unflexible character, I would advice to rig it in a pose where every limb is halfway in between highest and lowest angle possible. Don't rig in t-pose, when the character cannot stretch its arms that far, try to use minimum stretch (deformation of faces). $\endgroup$ Nov 3, 2021 at 14:58
  • $\begingroup$ @Stephen Just doing a straight conversion to A pose, after all other modelling, doesn't really help-- the issues are built into the mesh. But if you want to convert a T to an A, you can, just do some modelling clean-up afterwards. There are potential okay things to do that are that simple, like creating a UV map from an A pose on a T posed model to minimize distortion in the armpits. $\endgroup$
    – Nathan
    Nov 3, 2021 at 16:13
  • $\begingroup$ Speaking of armpits I'm using a t pose on my model how do I fix the gap and weird mesh around the chest and shoulders? Without using drivers because i don't know python. $\endgroup$
    – Stephen
    Nov 4, 2021 at 18:45

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