xpLimit

xpLimit can limit the movement of particles by preventing them from moving in one or more planes.

General tab

Untitled

xpLimit General tab menu.

Enabled

Checking this box activates xpLimit.

Mode

Set at Independent, by default.

You can change this to Action-Controlled.

Independent Mode

In this mode, particles will be affected if they come into the field of effect of the modifier.

Action-Controlled Mode

When in the Action-Controlled Mode setting, the modifier will only act on a particle when told to do so by an action.

Limit Positions

Check this box to enable position limiting.

Use Emitter Space

If unchecked, the axes on which movement is limited will be the global, 3D world, axes.

If it is enabled, the emitter axis is used instead.

You will only see a difference if the emitter is rotated so its axes are not aligned with the world axes.

Axis Limit

This is the limit, in percentage terms, of movement on the three axes.

A value of zero means no limit, whereas a value of 100% results in no movement at all on that axis.

The three components (X, Y, and Z axes) of the Axis Limit parameter can be mapped individually.

In this animation, there are no limits set on the Axis Limit parameters.

In this scene, there is 100% Axis Limit on the X axis.

Here, there is 100% Axis Limit on the Y axis.

Finally, 100% Axis Limit set on the Z axis.

X-Axis Restriction, Y-Axis Restriction, Z-Axis Restriction

Each parameter is set at None, by default.

The alternative settings are: X+ (or Y+ or Z+), and X- (or Y- or Z-).

X+ (Y+, Z+)

Movement is restricted to the positive axis.

This can be combined with the Axis Limit setting to reduce movement along the other axes.

Animation to demonstrate X-Axis Restriction set on X+.

Here, Y-Axis Restriction is set on Y+.

X- (Y-, Z-)

Movement is restricted to the negative axis.

This can be combined with the Axis Limit setting to reduce movement along the other axes.

This scene shows X-Axis Restriction on X-, directly comparing with the above.

Similarly, in comparison to the scene above, here is Y-Axis Restriction on Y-.

No Banking

When particles turn to move in a different direction, the bank component of their rotation is often changed automatically.

This looks natural for such things as birds but, if you watch a school of fish, they do not appear to bank on turning.

If you would prefer that the particles emulate that behaviour and don’t bank when turning, you can use this modifier with No Banking enabled.

No Banking is disabled here.

No Banking is enabled in this animation.

Scale tab

In this tab you can apply limits to the particle’s scale.

Untitled

xpLimit Scale tab menu.

Limit Scale

Check this box to enable scale limiting.

Limit Upper Scale

To limit the maximum scale of the particle, Check this box.

Upper Limit

If Limit Upper Scale is enabled, this is the maximum scale of the particle.

With Limit Upper Scale enabled, in this scene, xpScale is changing the scale of the xpGenerator generated pyramid objects as they move through 3D space. xpLimit is keyframed to reduce the upper limit of the Y axis scale.

Limit Lower Scale

To limit the minimum scale of the particle, check this box.

Lower Limit

If Limit Lower Scale is enabled, this is the minimum scale of the particle.

Rotations tab

In this tab you can limit the rotation applied to a particle.

Untitled

xpLimit Rotations tab menu.

Limit Rotations

Check this box to enable rotation limiting.

Limit H Positive

When enabled, particle positive rotation around the H-axis will be limited to the value in Positive Limit.

Positive Limit

The limiting value to use when Limit H Positive is enabled.

Limit H Negative, Negative Limit

As for Limit H Positive and Positive Limit, but for negative rotation around the H-axis.

Limit P Positive, Positive Limit, Limit P Negative, Negative Limit, Limit B Positive, Positive Limit, Limit B Negative, Negative Limit

As for rotation around the H-axis, for the P and B axes.

Other Data tab

You can use this tab to limit the value of several particle data parameters to within upper and/or lower limits.

Untitled

xpLimit Other Data tab menu.

Limit Other Data

Check this box to enable the limiting of other particle data.

Parameter to Limit

Set to Speed, by default, you can choose the data item to limit.

The other options are: Radius, Mass, Temperature, Smoke, Fuel, Fire and User Value.

In this final animation, with Parameter to Limit, set to Speed, Clip Higher Values is enabled and Value keyframed to slow the speed of the particles.

Clip Lower Values

If enabled, the selected parameter will be clamped to no lower than the value in the Value parameter.

Value

The lower limit value to use.

Clip Higher Values

If enabled, the selected parameter will be clamped to no higher than the value in the Value parameter.

Value

The upper limit value to use.

Groups Affected tab

Groups

To specify the group, drag and drop the desired Group object into this field.

This setting is useful if you want to ensure that the spawned particles are, or are not, affected by xpLimit.

Mapping tab

The modifier’s settings can be mapped to particle data.

Use the dedicated manual page, below, for instructions on how this works.

Data Mapping

Fields tab

You can use the Fields options to control where xpLimit operates.