Method

This node generates trails of lines or points along the path of individual particles to create trail-like effects. This is done by sampling the particle position at regular time intervals and storing the samples as control points in a path buffer. The size of the path buffer is finite so only a limited number of control points per particle may be stored, which in turn limits the visual length of the generated trail. The rate at which samples are taken is controlled by the Control Point Time Spacing parameter. There is also a threshold applied to the distance in 3D space between samples which is controlled using the Distance Threshold parameter. By increasing these thresholds new control points are added less regularly, allowing the trail to become longer. Control points slowly die over time, fading out the end of the trail. This is controlled by the Trail Decay parameter. The Particle Use Amount parameter is used to limit the number of particles that generate trails.

Particles can be sorted in back to front rendering order if Sort Particles is enabled, allowing transparent particles to render and blend together correctly. The Blend Mode parameter is used to control the blend mode between individual particles and also between the particles and the rest of the scene. The Particle Alpha parameter can be used to control the transparency of individual particles, scaling the alpha value already on the particle’s colour channel. Lines may be rendered as thin single pixel lines, or thickened and rendered as quads with softened edges, or the trail may be rendered as individual control points, determined by the Primitive Types parameter. When rendered as thick lines the line thickness may be controlled by the Line Thickness parameter.

Example
This image is taken from the “tornado.dfx” sample project.

Attributes

Name Description
Particle Alpha Change the alpha value for the particles.
Blend Mode Edit the blend mode used for the particles. See Blend Modes for details.
Primitive Types Change the shape that trails behind the particle.
  • Lines, single pixel lines trail the particles.
  • Thick Lines, particles with variable thickness follow the particles.
  • Thick Lines (Simplified), Uses simplified thick lines to generate to particle lines.
  • Extruded Geometry, Extrudes a geometric shape along the particle lines.
Line Thickness Edit the thickness of the line rendered. Only functions if Use Thick Lines is turned on.
Line Softness Change the thickness of the gradient along the edge of the line.
Luminance How bright the drawn trail is.
Luminance Randomness How much rnadomness there is in the brightness of the drawn trail.
Sort Key Value Biases the depth-based render order, to force the particle system to be drawn before or after other objects in the scene.
Depth Bias Offsets particles in depth so they are closer or further away from the camera, changing the point at which they intersect with the rest of the scene.
Cast Shadows Control whether shadows are cast.
Sort Particles Toggle whether the particles are sorted by depth from camera from back to front before rendering, enabling transparent particles to be rendered correctly.

Trail Properties

Name Description
Control Point Time Spacing The minimum time allowed between control point samples.
Trail Fade Mode Select how the trail fading is calculated.
  • Time, Trail fades based on the timeline.
  • Length, Trail fades on the length of the trail.
  • Age, Trail fades based on the age of each particle.
Trail Decay The rate of decay for control point samples. Only functions with Time set in Trail Fade Mode.
Trail Fade Length Set the length at which the particles fade off at. Only functions with Length set in Trail Fade Mode.
Trail Fade Age Set the age at which the particles fade at. Only functions with Age set in Trail Fade Mode.
Trail Fade Range How aggressively the particles fade away.
Num Trail Vertices Change the number of vertices generated to form the trail.
Particle Use Amount Percentage of particles that can be used by the node.
Num Radial Segments Change the number of sides to the extruded geometry. Extruded Geometry must be selected in the Primitive Types attribute.

Inputs

Name Description Typical Node Input
Material Input a material to be used by the trail when in Extruded Geometry mode. Materials
Rendered Emitters Specify which emitters are rendered using this renderer. By default, all emitters connected to the same particle root as the renderer are rendered. Primitive Emitter
Transform Modifier Links all transform properties to the input node. Null
Target Node Always faces the x-axis towards the inputs anchor point. Null
Local Transform Override Override the transformation values of the node, relative to its parent. Null

Outputs

In general, this node does not create usable outputs, but in Extruded Geometry mode this node generates geometry which can be Deformed or used as an input source for other effects.