Want to add offset for an object following other object's movements.

Dibyendu Saha

Hello, I want to make an object follow the position, rotation, and scale of another object or face mesh with a damping transformation effect.
I have imported my model, assigned it as a follower object, and created a face mesh (default), assigned it as the target object. I have used the script below to do the effect.

// -----JS CODE-----
// @input SceneObject follower
// @input SceneObject target

//@ui {"widget":"separator"}

// @input bool followPosition = true
//@ui {"widget":"group_start", "label":"Position Smoothing Properties", "showIf" : "followPosition"}
// @input float maxPosSpeed = 50 {"label":"Max Speed"}
// @input float posDamping = 5 {"label":"Damping"}
//@input int posMode = 0 {"widget":"combobox", "values":[{"label":"World Space", "value":0}, {"label":"Local Space", "value":1}], "label":"Mode"}
//@ui {"widget":"group_end"}

//@ui {"widget":"separator"}

// @input bool followRotation = true
//@ui {"widget":"group_start", "label":"Rotation Smoothing Properties", "showIf" : "followRotation"}
// @input float maxRotSpeed = 50 {"label":"Max Speed"}
// @input float rotDamping = 5 {"label":"Damping"}
//@input int rotMode = 0 {"widget":"combobox", "values":[{"label":"World Space", "value":0}, {"label":"Local Space", "value":1}], "label":"Mode"}
//@ui {"widget":"group_end"}

//@ui {"widget":"separator"}

// @input bool followScale = true
//@ui {"widget":"group_start", "label":"Scale Smoothing Properties", "showIf" : "followScale"}
// @input float maxScaleSpeed = 50 {"label":"Max Speed"}
// @input float scaleDamping = 5 {"label":"Damping"}
//@input int scaleMode = 0 {"widget":"combobox", "values":[{"label":"World Space", "value":0}, {"label":"Local Space", "value":1}], "label":"Mode"}
//@ui {"widget":"group_end"}

var followerTrans;
var targetTrans;
var dampRotVec4;
var isInit = false;
var positionVelocity = vec3.zero();
var rotationVelocity = vec4.zero();
var scaleVelocity = vec3.zero();
var dampPos;
var dampScale;
var deltaTime = getDeltaTime();

function initialize() {
isInit = validateInputs();
if (!isInit) {
return;
}
followerTrans = script.follower.getTransform();
targetTrans = script.target.getTransform();

dampRotVec4 = new vec4(script.rotDamping, script.rotDamping, script.rotDamping, script.rotDamping);
dampPos = script.posDamping;
dampScale = script.scaleDamping;

}

function onUpdate() {
if (!isInit) {
return;
}
deltaTime = getDeltaTime();
smoothPosition();
smoothRotation();
smoothScale();
}

function smoothPosition() {
if (!script.followPosition) {
return;
}

positionVelocity = positionVelocity.clampLength(script.maxPosSpeed);

var followerPosition = (script.posMode == 0) ? followerTrans.getWorldPosition() : followerTrans.getLocalPosition();
var targetPosition = (script.posMode == 0) ? targetTrans.getWorldPosition() : targetTrans.getLocalPosition();
var dir = followerPosition.sub(targetPosition)
var dampedVelocity = positionVelocity.sub(dir).uniformScale(dampPos * dampPos * deltaTime);
var dampedDelta = 1 + (dampPos * deltaTime);
var dampedDeltaVec = new vec3(dampedDelta, dampedDelta, dampedDelta);
positionVelocity = dampedVelocity.div(dampedDeltaVec.mult(dampedDeltaVec));
var finalPos = followerPosition.add(positionVelocity.uniformScale(deltaTime));



if (script.posMode == 0) {
    followerTrans.setLocalPosition(finalPos);
} else {
    followerTrans.setLocalPosition(finalPos);
}

}

function smoothRotation() {
if (!script.followRotation) {
return;
}

rotationVelocity = rotationVelocity.clampLength(script.maxRotSpeed);

var followerVector = (script.rotMode == 0) ? quat2Vec4(followerTrans.getWorldRotation()) : quat2Vec4(followerTrans.getLocalRotation());
var targetVector = (script.rotMode == 0) ? quat2Vec4(targetTrans.getWorldRotation()) : quat2Vec4(targetTrans.getLocalRotation());
if (deltaTime <= 0) {
    return;
}
var deltaTimeVec4 = new vec4(deltaTime, deltaTime, deltaTime, deltaTime);

var dot = followerVector.dot(targetVector);

if (dot < 0) {
    targetVector = targetVector.uniformScale(-1);
}

var dampedDelta = dampRotVec4.mult(dampRotVec4).mult(deltaTimeVec4);
var dampedVelocity = rotationVelocity.sub(followerVector.sub(targetVector)).mult(dampedDelta);
var dampedDelta = vec4.one().add(dampRotVec4.mult(deltaTimeVec4));
var multDampedDelta = dampedDelta.mult(dampedDelta);
rotationVelocity = dampedVelocity.div(multDampedDelta);
var finalRot = followerVector.add(rotationVelocity.mult(deltaTimeVec4)).normalize();

if (script.rotMode == 0) {
    followerTrans.setWorldRotation(new quat(finalRot.w, finalRot.x, finalRot.y, finalRot.z));
} else {
    followerTrans.setLocalRotation(new quat(finalRot.w, finalRot.x, finalRot.y, finalRot.z));
}

}

function smoothScale() {
if (!script.followScale) {
return;
}

scaleVelocity = scaleVelocity.clampLength(script.maxScaleSpeed);

var followScale = (script.scaleMode == 0) ? followerTrans.getWorldScale() : followerTrans.getLocalScale();
var targetScale = (script.scaleMode == 0) ? targetTrans.getWorldScale() : targetTrans.getLocalScale();

var dir = followScale.sub(targetScale);
var dampedVelocity = scaleVelocity.sub(dir).uniformScale(dampScale * dampScale * deltaTime);
var dampedDelta = 1 + (dampScale * deltaTime);
var dampedDeltaVec = new vec3(dampedDelta, dampedDelta, dampedDelta);
scaleVelocity = dampedVelocity.div(dampedDeltaVec.mult(dampedDeltaVec));
var finalScale = followScale.add(scaleVelocity.uniformScale(deltaTime));

if (script.scaleMode == 0) {
    followerTrans.setWorldScale(finalScale);
} else {
    followerTrans.setLocalScale(finalScale);
}

}

function quat2Vec4(q) {
return new vec4(q.x, q.y, q.z, q.w)
}

function validateInputs() {
if (!script.follower) {
print("ERROR: Please set a scene object that you want to follow the target.");
return false;
}
if (!script.target) {
print("ERROR: Please set a scene object as a target.");
return false;
}

return true;

}

initialize();

var updateEvent = script.createEvent("UpdateEvent");
updateEvent.bind(onUpdate);

The problem is that the follower object is moving and getting stuck to the target object. I want it to stay in its position and just follow the movement of the target object. Can anyone modify the script to achieve the result?
Please help..

Bakari Mustafa

You can control the smooth damping behavior by adjusting the values of the input parameters maxPosSpeed, posDamping, maxRotSpeed, rotDamping, maxScaleSpeed, and scaleDamping. The posMode, rotMode, and scaleMode input parameters allow you to specify whether the smooth damping should be applied in world space or local space.

Dibyendu Saha

I don't want to control the damping. My problem is that the follower object is moving and getting stuck to the target object. I want it to stay in its position and just follow the movement of the target object. Can anyone modify the script to achieve the result?

Bakari Mustafa

Sure! Here's one way you can modify the script to make the follower object follow the movement of the target object without getting stuck to it:

function smoothPosition() {
    if (!script.followPosition) {
        return;
    }

    var followerPosition = (script.posMode == 0) ? followerTrans.getWorldPosition() : followerTrans.getLocalPosition();
    var targetPosition = (script.posMode == 0) ? targetTrans.getWorldPosition() : targetTrans.getLocalPosition();
    var finalPos = targetPosition;

    if (script.posMode == 0) {
        followerTrans.setWorldPosition(finalPos);
    } else {
        followerTrans.setLocalPosition(finalPos);
    }
}

This code simply sets the position of the follower object to the position of the target object, without using any velocities or damping. This way the follower object will always be in the same position as the target object, without getting stuck to it.

You will also have to remove the following lines of code in the onUpdate() function:

positionVelocity = positionVelocity.clampLength(script.maxPosSpeed);
var dir = followerPosition.sub(targetPosition)
var dampedVelocity = positionVelocity.sub(dir).uniformScale(dampPos * dampPos * deltaTime);
var dampedDelta = 1 + (dampPos * deltaTime);
var dampedDeltaVec = new vec3(dampedDelta, dampedDelta, dampedDelta);
positionVelocity = dampedVelocity.div(dampedDeltaVec.mult(dampedDeltaVec));

And remove the following line in the smoothPosition function:

var finalPos = followerPosition.add(positionVelocity.uniformScale(deltaTime));

This should give you the desired result of having the follower object follow the movement of the target object without getting stuck to it.