nxSpeed

nxSpeed changes the speed of your NeXus particles, speeding them up or slowing them down. It works as a stack of layers, so you can combine several speed operations and blend them together.

Add it from Add ▸ INSYDIUM NeXus ▸ nxSpeed. It arrives as an empty. Add one or more speed layers, set each to an operation, then blend them. All of its settings live in Properties ▸ Physics.

A stream of particles picking up speed as an Incremental layer adds to their speed each frame, breaking over Suzanne.

Object Properties

The nxSpeed Object Properties panel with an Incremental layer

The nxSpeed panel in Properties ▸ Physics, on the Object Properties tab, showing an Incremental layer.

Enabled

Turns nxSpeed on or off. Disable it to switch off its effect without deleting it.

Layers

The stack of speed layers. Use the + button to add a layer, choosing its operation from the menu that appears, and the - button to remove the selected one. Each layer has an enable toggle on the right of its row, so you can switch a layer on or off without removing it.

Layers are processed from the top of the stack down, each blending with the result of the layers above it. Select a layer to show its settings underneath.

Layer Settings

These settings apply to the layer selected in the Layers list. The top block is shared by every layer. The controls below it change with the Layer Type.

Layer Type

Sets the operation this layer performs. A new nxSpeed starts with an Incremental layer. The layer types are Incremental, Absolute, Exponential, Use Spline and Range, each described below.

Blend

Sets how this layer combines with the layers above it. Set as Normal, by default. The other options are Add, Subtract, Multiply, Difference, Screen, Overlay, Min and Max.

Strength

Sets how strongly this layer contributes to the blend. Defaults to 100%.

Incremental

The default operation. It adds the Speed Value to each particle’s speed every frame, so the particles build up (or lose) speed for as long as they are affected.

Speed Value

The amount added to a particle’s speed each frame. Defaults to 1.5m. Keep it low, since the speed can build up quickly. Use a negative value to slow the particles down.

0.5m

The Speed Value is 0.5m, on the left, and 3m, on the right. A small value speeds the stream up gently, so it travels a short way. A large value accelerates it hard, throwing the particles much further.

Variation

Adds a random amount to the speed change, so the particles do not all speed up at the same rate. Defaults to 0%.

Absolute

Sets each particle’s speed directly to the Speed Value, rather than building it up. It uses the same Speed Value and Variation controls as Incremental, but the value becomes the particle’s new speed instead of an amount added each frame.

Exponential

Multiplies each particle’s speed every frame, for an accelerating or decelerating change.

The nxSpeed panel with an Exponential layer

An Exponential layer, with its single Acceleration control above the shared speed clamps.

Acceleration

The factor that multiplies the speed each frame. Defaults to 5. A positive value accelerates the particles, building up speed exponentially. A negative value decelerates them, slowing them to a halt.

Use Spline

Drives each particle’s speed from a curve, mapping the curve up to a maximum speed.

The nxSpeed panel with a Use Spline layer

A Use Spline layer, driving the speed from the Speed Spline curve up to Speed Max.

Speed Spline

The curve that shapes the speed over the particle’s life.

Speed Max

The speed the top of the curve maps to. Defaults to 3m.

Variation

Adds a random amount to the speed, so the particles do not all follow the curve identically. Defaults to 0%.

Range

Transitions each particle’s speed from a Speed Start to a Speed End over a time window.

The nxSpeed panel with a Range layer

A Range layer set to Particle Age, transitioning from Speed Start to Speed End over the time window, with an Ease curve shaping the change.

Speed Time

Sets what the transition is timed against. Set as Particle Age, by default. The other options are On Birth and Frame Time.

On Birth: measured from the particle’s birth. Only the Speed End and its Variation are used, so the Speed Start, the timing controls, Clamp Mode, Ease and the speed clamps below are all hidden.
Particle Age: measured by how old each particle is.
Frame Time: measured in scene frames.

Speed Start

The speed the particle transitions from, with its own Variation for a per-particle spread.

Speed End

The speed the particle transitions to, with its own Variation for a per-particle spread.

Start Time / End Time

The window over which the transition happens.

Time Variation

Adds a random spread to the transition timing, so the particles do not all change at the same moment. Defaults to 0%.

Clamp Mode

Sets how the ease curve behaves outside the time window. Set as Clamp, by default. The other options are Clamp In Range, Repeat and Continue.

Ease

A curve that eases the transition between Speed Start and Speed End.

Speed Clamps

Incremental, Absolute, Exponential and Range layers each end with a pair of speed clamps, so a speed change cannot push a particle beyond a set range.

Clamp Min

Stops a particle’s speed falling below a floor. Off by default. Enable it, then set the floor in Particle Speed Min, with its own Variation.

Clamp Max

Stops a particle’s speed rising above a ceiling. Off by default. Enable it, then set the ceiling in Particle Speed Max, with its own Variation.

Groups Affected

Use the Groups Affected tab to restrict nxSpeed to particles in specific nxGroup groups, rather than affecting every particle.

Mapping

Use the Mapping tab to drive nxSpeed’s settings from particle data instead of fixed values, so a particle’s own attributes can change the speed it feels. See Mapping for how this works.

Falloff

Use the Falloff tab to limit where nxSpeed acts. Add one or more nxFalloff objects to the list and blend them, so the speed change only affects particles inside the falloff region.