Cameras: cameraDirection will now properly decrease when gravity is applied #14508
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Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s). |
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| if (this.inertia === 0) { | ||
| this._updatePosition(relativeInertia, scaleFactor); | ||
| this.cameraDirection.scaleInPlace(0); | ||
| } else { | ||
| this.cameraDirection.scaleInPlace(relativeInertia); | ||
| this._updatePosition(relativeInertia, scaleFactor); | ||
| } |
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that's technically the only change that was needed to go back to the way things were before
Recently an issue was found where the FreeCamera was not slowing down when gravity was active. This PR modifies the
_collideWithWorldfunction to fix that issue.Forum Link: https://forum.babylonjs.com/t/bug-free-camera-never-stop/45546/4
Proof for using deltaTime ratio as scaling factor for gravity:
Given the following variables:
r = initial offset
n = inertia
a = relative inertia (with respect to frame deltaTime ratio; currentDeltaTime/standardDeltaTime) = n^t
s = scale factor
t = deltaTime ratio = currentDeltaTime/standardDeltaTime
g = gravity
x = scaling ratio to apply to gravity
Working from our previous proof for relative inertia and scale factor (#14482), we know that a frames worth of work looks something like:
sra = rn^t + ... + rn
When working with gravity applied, the equation will look more like:
sra + xg = (rn^t + g) + ... + (rn + g)
xin this scenario is some ratio to multiply gravity by so that the same amount of gravity is applied to each frame as though it was 60 FPS. Next, let's reorganize things:sra + xg = rn^t + ... + rn + (g + ... + g) = rn^t + ... + rn + t*g
We know that there are t terms for our geometric sum so that means if we are adding gravity to each, we have
tnumber ofgvalues. Therefore, we havetgat the end. By our first line, we know thatsra = rn^t + ... + rnso we can use substitution to make things cleaner:sra + xg = sra + tg
If we subtract
srafrom each side, we get:xg = tg
x = t
Therefore, since gravity is just a constant and is unaffected by inertia, we can just multiply it by
t(our deltaTime ratio).