Jump to content

ArcRotateCamera - Inertia dependend on FPS


Recommended Posts


I don't know if this is something that could be merged into github but we had some projects (and therefore customers) that

were highly loaded with objects, thus a bit slow in rendering.

The camera inertia was then to long lasting to control the camera if you know what I mean.

This is what I've changed to handle this:

// Inertia
            var engineDelta = Math.min(this.getEngine().deltaTime,100), inertiaFactor = Math.min(1,16.66666 / engineDelta);

            if (this.inertialAlphaOffset !== 0 || this.inertialBetaOffset !== 0 || this.inertialRadiusOffset !== 0) {
                this.alpha += (this.beta <= 0 ? -this.inertialAlphaOffset : this.inertialAlphaOffset) / inertiaFactor;
                this.beta += this.inertialBetaOffset     / inertiaFactor;
                this.radius -= this.inertialRadiusOffset / inertiaFactor;
                this.inertialAlphaOffset  *= this.inertia * inertiaFactor;
                this.inertialBetaOffset   *= this.inertia * inertiaFactor;
                this.inertialRadiusOffset *= this.inertia * inertiaFactor;

                if (Math.abs(this.inertialAlphaOffset) < BABYLON.Engine.Epsilon)
                    this.inertialAlphaOffset = 0;
                if (Math.abs(this.inertialBetaOffset) < BABYLON.Engine.Epsilon)
                    this.inertialBetaOffset = 0;
                if (Math.abs(this.inertialRadiusOffset) < BABYLON.Engine.Epsilon)
                    this.inertialRadiusOffset = 0;
            // Panning inertia
            if (this.inertialPanningX !== 0 || this.inertialPanningY !== 0) {
                if (!this._localDirection) {
                    this._localDirection = BABYLON.Vector3.Zero();
                    this._transformedDirection = BABYLON.Vector3.Zero();
                this.inertialPanningX *= this.inertia * inertiaFactor;
                this.inertialPanningY *= this.inertia * inertiaFactor;

                if (Math.abs(this.inertialPanningX) < BABYLON.Engine.Epsilon)
                    this.inertialPanningX = 0;
                if (Math.abs(this.inertialPanningY) < BABYLON.Engine.Epsilon)
                    this.inertialPanningY = 0;
                this._localDirection.copyFromFloats(this.inertialPanningX / inertiaFactor, this.inertialPanningY / inertiaFactor, 0);
                BABYLON.Vector3.TransformNormalToRef(this._localDirection, this._cameraTransformMatrix, this._transformedDirection);

It rotates by the given inertia amount depending on the time that proceeded during the renderings.


var engineDelta = Math.min(this.getEngine().deltaTime,100)

is to avoid big camera jumps on frames that last longer than 100ms. In our project the render loop doesn't run continuesly.


If someone likes to test this and/or push it into babylon I would be glad to have contributed a small thing :-)

If not it's also completely okay as it's only needed in our project(s)! ;-)


Best regards


Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...