ParticleGravity

With ParticleGravity, you can apply gravity to your particles. Unlike our familiar gravity, particle gravity works in any or all of the x, y and z directions, and you can also set negative values to them. When you connect the ParticleGravity node to your particle stream, an arrow appears in the Viewer, which you can then use to control the gravity. The bigger and longer the arrow, the stronger the gravity effect.

Inputs and Controls

Connection Type

Connection Name

Function

Input

particles

The particle system to which you intend to apply gravity.

Control (UI)

Knob (Scripting)

Default Value

Function

ParticleGravity Tab

display

display

unchanged

Adjust the display characteristics of the particles. These settings don’t affect the render output of the scene; these are for display purposes only in the 3D Viewer.

off - hides the particles.

wireframe - displays only the outlines of the particle.

solid - displays all particles with a solid color.

solid+wireframe - displays the particles as solid color with the particles outlines.

textured - displays only the surface texture.

textured+wireframe - displays the wireframe plus the surface texture.

unchanged - doesn't change the particles display mode. The Viewer can override this setting.

selectable

selectable

enabled

When enabled, you can select the particles in the Viewer by clicking on them.

render

render_mode

unchanged

Sets how the particles will render. This control is independent from the display selection, but has the same settings.

from xyz

from

N/A

Sets the point of origin for the vector on the x, y, and z axes.

to xyz

to

N/A

Sets the acceleration to be applied to all particles, depending on the direction and magnitude of the vector applied - the bigger and longer the arrow, the stronger the gravity effect.

The position of the vector has no effect and Gravity affects all particles equally, irrespective of mass.

Conditions Tab

probability

probability

1

Sets the probability that this node affects your particles. If you set this to zero, the node won’t affect any particles, and if the value is 1, the node will affect every particle.

min age

min_age

0

Limits the effect of this node to particles above this minimum age. The age of the particle is its lifetime normalized between 0 and 1.

max age

max_age

1

Limits the effect of this node to particles below this maximum age. The age of the particle is its lifetime normalized between 0 and 1.

random seed

seed

0

Sets the integer to change the results of generated randomness in your particles. You can achieve slightly different effects by changing this number.

channels

channels

all

Specifies which particle channels the effect of this node should be applied to. Channels a and b are arbitrary names for channels which are useful if you want different ParticleEmitter nodes or other particle force nodes to have an effect on separate channels.

Region Tab

region

region

none

Sets the region which you want to use to confine the particle effect to. For example, if you choose a sphere, only particles inside that sphere shaped region will be affected by particle effects.

none - all particles are affected as normal.

sphere, box, half-space, and cylinder - controls the region’s boundary shape.

invert region

region_invert

disabled

When enabled, particles outside the region are affected rather than those inside it.

file_menu

N/A

Select to import or export a channel file:

Import chan file - import a channel file and transform the region marker according to the transformation data in the channel file. Channel files contain a set of Cartesian coordinates for every frame of animation in a given shot. You can create and export them using Nuke or 3D tracking software, such as 3D-Equalizer, Maya, or Boujou.

Export chan file - export the translation parameters that you’ve applied to the region marker as a channel file. This is a useful method of sharing setups between artists.

snap_menu

N/A

Match selection position - the region marker is snapped to a new position depending on the points selected.

Match selection position, orientation - the region marker is snapped to a new position and orientation depending on the points selected.

Match selection position, orientation, size - the region marker is snapped to a new position, orientation, and size depending on the points selected.

transform order

xform_order

SRT

Sets the operation order for scale (S), rotation (R), and translation (T). The possible operation combinations are SRT, STR, RST, RTS, TSR, TRS.

rotation order

rot_order

ZXY

Sets the order of rotation. The possible axial combinations are ZXY, XYZ, XZY, YXZ, YZX, ZXY, ZYX.

translate

translate

0, 0, 0

Lets you translate the region marker along the x, y, and z axes. You can also adjust translate values by clicking and dragging the axis in the 3D Viewer.

rotate

rotate

0, 0, 0

Lets you rotate the region marker around the x, y, and z axes. You can adjust rotate values by holding down Ctrl/Cmd and dragging in the 3D Viewer.

scale

scaling

1, 1, 1

Lets you scale the region marker on the x, y, and z axes.

uniform scale

uniform_scale

1

Lets you scale the region marker simultaneously on the x, y, and z axes.

skew

skew

0, 0, 0

Lets you skew the region marker on the x, y, and z axes.

pivot

pivot

0, 0, 0

When you make changes to the region marker’s position, scaling, skewing, and rotation, these occur from the location of the object’s origin point or pivot. The pivot x, y, and z controls allow you to offset the pivot point and move it anywhere you like - you can even move it outside of the object. Subsequent transformations applied will then occur relative to the new pivot point location.

You can also hold down Ctrl/Cmd+Alt and drag the pivot point to a new location in the 3D Viewer.

Local Matrix

specify matrix

useMatrix

N/A

Enable this control to specify matrix values for the object you’re transforming as an alternative to setting transform, scale, skew and pivot values above.

matrix

matrix

N/A

The matrix displays values from the object’s transform, rotate, scale, skew, and pivot controls.

Check specify matrix and copy or drag-and-drop matrix values from another object to apply those values, for example, if you wanted to align objects in a scene.

Step-by-Step Guides

Applying Gravity to Particles

Video Tutorials

Example Nuke Scripts

Applying gravity to particles