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--- democap:preparecharacter [2022/03/25 15:04] – [Base Inverse Kinematics (IK) Pose] dragonlord
+++ democap:preparecharacter [2025/03/23 16:23] (current) – [Side Effects With Bending] dragonlord
@@ Line 82: / Line 82: @@
 Legs should be bend strongly as if the character is doing a low crouch. Extreme pose is okay here, especially for beast type legs. If you can not define a sane crouch pose here the motion capture is not going to achieve good results either.
+====== Looking Up-Down ======
+For beast type characters with long necks it is useful to define the up and down looking animation to get artistic control over how the head movement performed by the actor is mapped to the character. For this create an animation action with these 3 poses: looking down (left end of the animation), neutral looking ahead (middle of the animation) and looking up (right end of the animation). Using 50 frames in total is usually enough for this. It is recommended to use linear interpolation between the poses since DEMoCap maps the up-down looking angle to the animation frame time. In some situations though it might help to choose a different interpolation. It is also a good idea to set the channel to linear extrapolation. If constant extrapolation is used (the default) Blender has the tendency to smooth out the motion towards the border of the animation which can have negative effect. By using linear extrapolation this is prevented.
+The image below shows how this animation looks like for a typical long neck character.
+{{ :democap:look_up_down.png?direct |}}
+====== Shift Head Forward-Backward ======
+For all kinds of characters using a shift head forward-backward animation allows DEMoCap to capture actor head shifting forward-backward to apply it to the character. Since it is difficult for DEMoCap to predict how such a motion looks like for an actor it is required to create an animation for this if desired to be captured. For this create an animation action with these 3 poses: shift head forward (left end of the animation), neutral looking ahead (middle of the animation) and shift head backward (right end of the animation). Using 50 frames in total is usually enough for this. It is recommended to use linear interpolation between the poses since DEMoCap maps the up-down looking angle to the animation frame time. In some situations though it might help to choose a different interpolation. It is also a good idea to set the channel to linear extrapolation. If constant extrapolation is used (the default) Blender has the tendency to smooth out the motion towards the border of the animation which can have negative effect. By using linear extrapolation this is prevented.
+The image below shows how this animation looks like for a long neck character. The same applies to normal characters just with head/neck bone modified.
+{{ :democap:head_for_back.png?direct |}}
+===== Side Effects With Bending =====
+<WRAP float right>
+{{ :democap:look_up_down_modified.png?direct |}}
+</WRAP>
+Using shift head forward-backward animation and looking up-down animation together can yield results which might not be as you expect them to be. The reason is that when looking up your head will also do some shifting which DEMoCap will detect. As a result looking up will usually be a combination of the looking up-down animation and the shift head forward-backward animation. To counter this you have to subtract a certain amount of head shift forward-backward from the looking up-down animation to get exactly the result you want to. To do this you best use the [[democap:blender_democaptools#copy_bone_matrices|Blender DEMoCap Tools: Copy Bone Matrices]] and company operators.
+First make a copy of your look up-down animation and rename it to something like "look up-down modified" or similar. This animation is going to be the one to use if both looking up-down and shift head forward-backward is used. Usually it is enough to just modify the looking up pose but correctly the looking down pose would need a correction too, albeit a lesser one.
+  * Switch to your shift head forward-backward action.
+  * Select the frame where your character is shifting head forward by roughly 75%.
+  * Select all neck bones and the head bone to modify.
+  * Click ''Copy Bone Matrices'' to copy the pose.
+  * Select the frame in the middle where your character is in neutral pose.
+  * Click ''Copy Subtract''. You have now the difference stored in the copy buffer.
+  * Switch to your looking up-down action.
+  * Select the frame at the right end where your character is looking up.
+  * Click ''Paste Bone Matrices'' and make sure that in the operator panel ''Overlay'' and ''Negate'' are ticked.
+  * Press ''K'' to add rotation keyframes.
+The animation frame should now looking similar to the image on the right side.
+It looks a bit strange but if this animation frame is combined with shifting head forward (as happens if you look up) then the result will be the looking up pose you started out with.
+You have now the animation adjusted. Export the animations and in the motion transfer select this new animation as ''Neck Bend X Move''.
+How much of the head shifting to subtract depends on the actor. In general the rule of thumb is to subtract 75% of shift head forward from the looking up pose and 50% of shift head forward from the looking down pose. As mentioned the looking done pose is often not required to be modified but it can be done to optimize the results.
+<WRAP clear/>

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