From cf0863567daffb26c3bae4de0041cb4ebaf4f0bb Mon Sep 17 00:00:00 2001
From: Vidya Narayanan <vidyan@cmu.edu>
Date: Tue, 17 Nov 2020 15:14:30 -0500
Subject: [PATCH] guide edits for IK, todo video
---
docs/guide/animate.md | 9 ++++++---
docs/guide/rig.md | 11 ++++++++---
2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/docs/guide/animate.md b/docs/guide/animate.md
index 61b7faa..a975d80 100644
--- a/docs/guide/animate.md
+++ b/docs/guide/animate.md
@@ -30,9 +30,12 @@ Check `Draw Splines` to visualize the spline along which objects are animated.
`Add Frames` inserts 90 empty frames into the timeline. `Crop End` deletes frames from the selected location to the end of the timeline.
-### Posing
-Once you have [rigged](../rig) an object with a skeleton, it can now be posed by selecting a joint and changing its pose i.e., rotating the joint.
-Once you've implemented **inverse kinematics** and **skinning**, as you change the pose, the mesh will deform.
+### Posing
+Once you have [rigged](../rig) an object with a skeleton, it can now be posed by selecting a joint and changing its pose i.e., rotating the joint. This is called Forward Kinematics.
+Joint poses can also be indirectly changed by using the IK (Inverse Kinematics) handles to provide target positions.
+Note that IK handles need to be explicitly enabled using the checkbox.
+
+Once you've implemented **forward kinematics**, **inverse kinematics** and **skinning**, as you change the pose, the mesh will deform.
Different poses can be set as keyframes to animate the object.
<video src="{{ site.baseurl }}/guide/animate-mode/guide-posing-rig.mp4" controls preload muted loop style="max-width: 100%; margin: 0 auto;"></video>
diff --git a/docs/guide/rig.md b/docs/guide/rig.md
index c57a0fa..8ed8e24 100644
--- a/docs/guide/rig.md
+++ b/docs/guide/rig.md
@@ -30,15 +30,20 @@ Each joint has an associated `Radius` which controls the part of the mesh influ
Note that rigging only uses extents of the bone for skeleton setup, joint pose does not influence the skeleton. Once rigging is done, the object can be posed by changing joint rotations in the [animate](../animate) mode.
+
+## Inverse Kinematics
+Instead of computing the positions of the bones from the joint poses (forward kinematics), in inverse kinematics, joint positions are computed from target positions.
+To associate a target position with a joint, select `Add IK` and edit the target position. Multiple target positions can be associated with the same joint but targets need to be explicitly enabled using the checkbox.
+In the [animate](../animate) mode, once inverse kinematics is implemented, joint rotation(pose) is updated based on the enabled IK handles.
+
+[TODO IK video]()
+
<!--
### Toggling Linear Blend Skinning with Threshold
You can press `u` or `U` to toggle between linear blend skinning with or without threshold.
-### Inverse Kinematics
-
-Multiple targets can be specified for IK purposes. To specify an additional target, just select a new joint and right click. To clear all targets, press `i` or `I`.
-->
--
GitLab