ArcRotateCamera - Inertia dependend on FPS

Hello,

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);
                this._viewMatrix.invertToRef(this._cameraTransformMatrix);
                BABYLON.Vector3.TransformNormalToRef(this._localDirection, this._cameraTransformMatrix, this._transformedDirection);
                this.target.addInPlace(this._transformedDirection);
            }

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

The

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

Kevin