rigify reverses the bend of the knees in IK #79092

New Issue

anger · 2020-07-19T23:16:20+02:00

anger commented

2020-07-19 23:16:20 +02:00

WINDOWS10
Nvidia GTX1070
Blender Version
Broken: 2.80 --->2.83.2

Worked: 2.79

Short description of error
rigify reverses the bend of the knees in IK. the poles are reversed and I don't know where the rest of the problem comes from
Exact steps for others to reproduce the error
Rigging a human character, generating the rig, taking the bone torso and trying to kneel the human character.
![Blender_EsquarkASSET_BlenderPERSONNAGECARA_2020-07-19_23-01-19.png

WINDOWS10 Nvidia GTX1070 **Blender Version** Broken: 2.80 --->2.83.2 Worked: 2.79 **Short description of error** rigify reverses the bend of the knees in IK. the poles are reversed and I don't know where the rest of the problem comes from **Exact steps for others to reproduce the error** Rigging a human character, generating the rig, taking the bone torso and trying to kneel the human character. ![Blender_[EsquarkASSET_BlenderPERSONNAGECARA_2020-07-19_23-01-19.png](https://archive.blender.org/developer/F8707458/Blender__EsquarkASSET_BlenderPERSONNAGECARA_2020-07-19_23-01-19.png)

anger commented

2020-07-19 23:16:20 +02:00

Added subscriber: @jemian

Joseph Brandenburg commented

2020-07-19 23:57:01 +02:00

Added subscriber: @Josephbburg

Joseph Brandenburg commented

2020-07-19 23:57:01 +02:00

This is not a bug, please see the manual for instructions on the proper positioning of bones: https://docs.blender.org/manual/en/latest/addons/rigging/rigify/bone_positioning.html#bone-positioning-guide

anger commented

2020-07-20 02:19:25 +02:00

It's not a bug? All the bones of the leg have a roll of 54 when generated, while on the metarig it's 0 and you say it's good.

anger commented

2020-07-20 02:23:52 +02:00

I never had a problem placing the metarig until the 2.8 arrived.

Joseph Brandenburg commented

2020-07-20 02:27:55 +02:00

The bending angle of Rigify limbs is no longer determined by the metarig's bone roll.
From the manual I linked above:

From version 0.5 and above there is no more need of manual bone rolls alignment, the generate function will take care of that for you evaluating it from bend axis; just insert a slight bend in your limb and it’s done! If you need more control on the orientation follow the guidelines described in Advanced Usage.

Please read the manual and follow its instructions closely. The unexpected behavior should not occur any longer.
.
Pro tip: Create a Plane object and line it up in the plane you want your bones IK to operate in. Then place the 3D cursor on the plane using Geometry orientation (with the 3D cursor tool). Now, with the Transform Orientation and Pivot Point both set to "3D Cursor" (, and . pie menus, respectively), scale the bones to 0 along the y axis of the 3D cursor. now they are correctly aligned, and any bend in the leg will now be correctly oriented.

Anyways, this isn't a help forum. That should be enough to get you going in the right direction... but please close this report as it is not a bug.

The bending angle of Rigify limbs is no longer determined by the metarig's bone roll. From the manual I linked above: > From version 0.5 and above there is no more need of manual bone rolls alignment, the generate function will take care of that for you evaluating it from bend axis; just insert a slight bend in your limb and it’s done! If you need more control on the orientation follow the guidelines described in Advanced Usage. Please **read the manual** and follow its instructions closely. The unexpected behavior should not occur any longer. . Pro tip: Create a Plane object and line it up in the plane you want your bones IK to operate in. Then place the 3D cursor on the plane using Geometry orientation (with the 3D cursor tool). Now, with the Transform Orientation and Pivot Point both set to "3D Cursor" (`,` and `.` pie menus, respectively), scale the bones to 0 along the y axis of the 3D cursor. now they are correctly aligned, and any bend in the leg will now be correctly oriented. Anyways, this isn't a help forum. That should be enough to get you going in the right direction... but please close this report as it is not a bug.

anger commented

2020-07-20 05:38:41 +02:00

yes well I do exactly as on the manual but it's been several times that I have this error while the metarig does not. Yet I barely move the bones exactly according to the manual. I will investigate more precisely when the error occurs.

anger commented

2020-07-20 05:58:36 +02:00

Ok I've got it. If there's a little y-rotation of bones thigh.L or thigh.R. the generation makes a bug and we find all the leg bones with a 54 roll.

anger commented

2020-07-20 06:08:57 +02:00

maybe we don't call it a bug but for me it's a very tricky setting and it's really hard to avoid it.

Ivan Cappiello commented

2020-10-05 10:30:43 +02:00

Added subscriber: @icappiello

Ivan Cappiello commented

2020-10-05 10:30:43 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Ivan Cappiello closed this issue

2020-10-05 10:30:43 +02:00

Ivan Cappiello self-assigned this 2020-10-05 10:30:43 +02:00

Ivan Cappiello commented

2020-10-05 10:30:43 +02:00

Usually these are wrong placement issues. All IKs require an active angle to let rigify detect where the limb is supposed to bend. This means that you should point knees and elbow to a direction. More rotations are implied more errors are produced. In the linked video the real problem is that the leg is straight. This means that rigify (and any other ik system based on bone position/orientation) can't detect automatically where it should point.
The manual makes pretty clear what's the requirement:

Rigify Manual

For the leg you can follow a similar process. Start by aligning the leg bones creating a straight line from the hips to the ankle, then place the foot and the toe accordingly. Remember to add a slight bend to the knee. This can be easily done by going in the side view, entering armature Edit Mode and sliding the bone junction between thigh and shin slightly toward the world’s Y axis.

If having an aligned leg it's not an option for you, in limb settings you can define manual alignment (usually x manual) then orient roll on the shin bone as the thigh bone manually (in edit mode first click on shin, then shift-click on thigh, then align to active bone through shift+N shortcut).
Remember that the knee bend is mandatory to make it work in both cases since even manual mode needs to know if it has to bend on positive or negative x.

I am closing this as invalid unless further issues pop up.

Usually these are wrong placement issues. All IKs require an active angle to let rigify detect where the limb is supposed to bend. This means that you should point knees and elbow to a direction. More rotations are implied more errors are produced. In the linked video the real problem is that the leg is straight. This means that rigify (and any other ik system based on bone position/orientation) can't detect automatically where it should point. The manual makes pretty clear what's the requirement: [Rigify Manual ](https://docs.blender.org/manual/en/latest/addons/rigging/rigify/bone_positioning.html#limbs-bones) > For the leg you can follow a similar process. **Start by aligning the leg bones creating a straight line from the hips to the ankle**, then place the foot and the toe accordingly. **Remember to add a slight bend to the knee**. This can be easily done by going in the side view, entering armature Edit Mode and sliding the bone junction between thigh and shin slightly toward the world’s Y axis. If having an aligned leg it's not an option for you, in limb settings you can define manual alignment (usually x manual) then orient roll on the shin bone as the thigh bone manually (in edit mode first click on shin, then shift-click on thigh, then align to active bone through shift+N shortcut). Remember that the knee bend is mandatory to make it work in both cases since even manual mode needs to know if it has to bend on positive or negative x. I am closing this as invalid unless further issues pop up.

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rigify reverses the bend of the knees in IK #79092