Relation Constraint Boxes
Videos
Comet's PoseReader relation box
Rigging for correction joints
Category - OpenMobu
A relation constraint box is based on Comet's PoseReader plugin for Autodesk Maya. The idea is to calculate the activation factor when a given transform's rotation is within specified cone limits.
This can be very useful for rigging, especially when working with correction joints where activation is linked to a joint's specific orientation. For example, it can be used to correct the shoulder's movement when the arm is raised upward.
A test scene is provided to demonstrate a rig setup on the left shoulder of a skeleton.
PoseTransform Box
You can create poses for an object that internally store the transformation matrix of that object. The relation box can then be used to calculate the final transform at runtime by blending between the stored transforms in the poses.
It supports up to 6 poses, which can be defined in the relation box properties (accessible in the property view of the selected relation box).
Category - OpenMobu
Sample scene - relationBox_PoseTransform.fbx
Look Rotation Box
Calculate a rotation to look at a given target point. This is similar to an Aim constraint, but in this case, it's presented in the form of a relation box.
Category - OpenMobu
Sample scene - relationBox_LookRotation.fbx
RayIntersect Box
Calculate the intersection point between a ray and a mesh.
Category - OpenMobu
Sample scene - relationBox_RayIntersect.fbx
Quaternion math boxes
Boxes Category - Quaternion
List of boxes:
Axis Rotation - make a quaternion of rotation of a given angle around given axis
Euler To Quaternion - convert euler angles into quaternion rotation. The node has property Rotation Order for the given euler angles.
Interpolate - interpolate between two quaternions
Invert - invert the quaternion
Look Rotation - It's similar to the functionality of an "aim constraint" where an object rotates to look at a target point, ensuring that its "up" orientation is correctly maintained.
Mult - multiply two quaternions
Normalize - make a unit quaternion
Quaternion To Euler - convert from quaternion rotation into euler angles. The node has property Rotation Order for the given euler angles.
RotateBy - rotate a given 3d vector by quaternion rotation
Sample scene - relationBox_QuaternionMath.fbx
RBF Box
Radial Basis Function (RBF) is a method for interpolating values in multidimensional space. In 3D graphics and skeleton rigging, RBFs are used to smoothly blend corrective deformations or poses based on joint rotations, ensuring natural and continuous skin deformation across a range of movements.
RBFs are particularly efficient for multidimensional interpolation, which is perfect for rigging systems that need to handle multiple influencing joints. For example, if the orientation of a joint depends on multiple axes (like bending and twisting), RBFs handle the blending of these orientations smoothly.
Category - OpenMobu
Boxes:
RBFVector - interpolate in 3 dimentional space
RBFVector 4 - interpolate in 4 dimentional space
In the @openmobu.txt configuration file, there is a property called Box RBF with a setting for number of connectors, where you can define how many input values you would like to interpolate. By default, it is set to 6 input values.
Box Properties:
Function Type - Gaussian, Multiquadratic, Inverse Multiquadratic. defines the way of weight distribution.
Height
The height parameter controls the amplitude or influence strength of the RBF at the center of the radial function. It determines how strongly the RBF affects the interpolation at the point where the distance from the center is zero.
In simple terms, height defines the peak value of the function. A higher height means the RBF has a stronger influence in its immediate vicinity.
Sigma
The sigma parameter controls the spread or width of the RBF. It determines how quickly the influence of the RBF decays as you move away from the center.
A smaller sigma value makes the RBF more concentrated around its center, meaning the influence drops off sharply as you move away. A larger sigma value creates a more gradual influence over a wider area.
Rotation Multiply - apply the multiplier to scale down targets
Sample scene - relationBox_RBF.fbx
Sphere Coords Box
Convert Euler rotation into spherical coordinates. This way, we can avoid the gimbal lock effect in rotations and establish relationships based on polar coordinates on the surface of a sphere. This approach could be a great fit for rigging correction joints.
Category - OpenMobu
Sample scene - relationBox_SphereCoords.fbx
Sample scene - relationBox_SphereCoords_ExtractRotationXZ.fbx
Spring Box
spring dynamics, secondary motion
A box for relation constraint 
Spring box math based on fundamental formule F = -kx
Sample scene - relationBox_Spring.fbx
Sample scene - relationBox_SpringAndCamera.fbx
Stiff
stiffness of the springs (the higher the value, the more rigid) Hardness is the reaction and the effect of the spring from which she draws a point in the original position.
0.1
Damp
the size of fading fluctuations spring (the more, the less hesitation commit spring) The essence of this parameter under a big question, in practice, it gives some the wrong result, so sometimes fading fluctuations can be regarded as a constant value of 0.10 for example.
0.0
Length
the length of the spring (should be set to 0) A value of zero reference position is the point of going, otherwise the spring will be busy trying to position a specified distance from moving
0.0
Mass
the mass. The more weight the more difficult it is to move the spring with a space or vice versa to return it to its original position.
1.0
Friction
force of resistance that allows “stifle” the dynamics of the spring and return it to its original position. The higher the number the less the effect of spring ”
0.1
EvalSteps
number of spring evaluation substeps per second
30.0
RealTime
checkbox to specify spring evaluation time. When checkbox is on, spring uses system time and play in realtime. When it’s off, spring uses player control local time from time slider (this is for plotting and animation playback).
on (1.0)
Zero Frame
frame on which we reset our simulation (for non realtime evaluation). This is when we rewind our animation to the very begining and want to start simulation from that “zero” point
0 (frame 0)
Pos
input position
Result
output position
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