Double Joints or Add a Bone between two Bones
In order to do that first we select the bone we want to rotate and press Shift + P, to clear the parent in Edit mode, and we move the joints to create a small separation between them.
This small fix will also help you in creating the inverse kinematics. The example depicts an imaginary leg, to make easier to identfy the different parts of the model, but you could repeat this in arms and other type of joints.
Model with better rotation on the joint
With inverse kinematics, the program calculates the position of the joints based in a given position and rotation relative to the start of the chain. How can we do this in blender? To explain it we will use the "leg" model we used before.
First we will select the feet joint in edit mode and press CTRL + E to extrude a new joint we will rename it feetIK, reapeat the shame to create a point in the knee to act as pole target. Then press SHIFT + P to clear parent of both joints. Move the KneeIK away from the model to where you want the leg to bend to.
Then got to pose mode and select the shin bone, go to the right panel bone constraint menu and select Inverse Kinematics. Select as the target the armature, and then pick the bone you want to control the IK, in this case the FeetIK.
Choose the armature as the pole target (where chain of bones will try to bend to), select the bone you want it to go, in this case the kneeIK.
Change the pole angle if the model rotates in a different angle. And change the chain length, if you have souble joints select 3, if not select 2.
Select the the feet bone in pose mode, and in bone Constraint properties select Copy rotation. Select the armature as the target and the feetIK as the bone.
If the Inverse kinematics is bends the wrong way or is going stray without bending that means that you joint needs to be closer, to the bending point. Go to edit mode and move the joint then check the inverse kinematics.
Final Inverse kinematics on the model
Custom Bone Shapes
In the last segment we saw how to create a bone to create the inverse kinematics but seeing a lot bones with the same shape can be confusing. But we can change the shape to make it easier to identify.
Once we have the meshes selected, go to the bones you cretaed before select the want you want to change the mesh of, and go to display properties, custom shape. There select the mesh you want to change it for.
Sometimes the mesh doesnt look right when you change it, but you can edit in on the original mesh an it will change on the bones too. Remember to apply the changes from the object menu anytime you change something. You can only view the custom shapes on pose mode.
Default Bone Display & Color Coding
To further edit your bones, you can change the shape you view them, just go to the menu on the right panel called Object Data Properties, it has running man as an icon, and click viewport display. There you can check in front to always see the bones in front of your model. and change their shape, by default they are octahedral.
You can also change the color of the shapes you made to substitute the bones, select the bone and on the Object data properties, bone groups, create a new group and change the defaul colour. It's recomendable if you have symmetric bone select diffrent color for the left and right side.
In blender you can save different poses, to access them inmediatly. In order to do that, put the bones in the pose you want to save, select the bones. Go to object Data Properties, pose library, there create a new pose library. Important check the shield on the right side the name, because if you don't change it even if you save the scene you will lose the pogress you made in the pose library.
I recommend to save the base rig in a initial pose, so that you dont lose the original rig.
Pose Library fo the leg
This are a small collection of tricks that I recopilated after having to animate some models that were needed in GLTF. It was a bit difficult since Blender is not friendly with people that learned maya or 3d max, or any kind of industry software.
Thought they are making advances in making it easier to learn this software, making it able to put the industry controls, for example. It still needs work.
Some controls change when you change to industry standards, that's why this guide it's for those that learned softwares like Maya but want or have to use blender, learn how the controls and where the basic things to work are.