"Nebula.System.update( delta )" affects particle position.

[MasatoMakino]

Expected Behavior

Reproduced particle position even if System.update(delta) changes in a variable frame rate environment.

Actual Behavior

When System.update(delta) changes, the particle position not reproduced.

Steps to Reproduce the Problem

1. get delta time from timestamp of requestAnimationFrame.
2. Nebula.System.update( delta );
3. If dropped frames, the position of the particles changes.

codepen

Here is the sample code.
Anyone can change the DELTA_COEFFICIENT value.

delta = 0.0167 (DEFAULT_SYSTEM_DELTA)

delta = 0.00551

Why

Nebula.Emitter.damping is not corrected by delta time.

integrate() function.

Velocity and Acceleration corrected by delta time.

In the sample code, if you change FIX_DAMPING = true, the particle positions will be reproduced.

Specifications

• Version: three-nebula v5.0.1 + three.js r108
• Platform: macOS 10.14.6
• Subsystem: Google Chrome 77.0.3865.90

[rohan-deshpande]

Hi! Thanks very much for this issue and the codepen, I'm looking into it, cc @manthrax

[rohan-deshpande]

Resolved by #149