Ribbon Type Data

RibbonSmoke.png

The Ribbon type data module indicates that the emitter should output trails - connecting particles to form ribbons. Particles are connected in the order of their birth. Therefore, the more erratic the initial velocity pattern of the particles, the more chaotic the ribbon.

The Ribbon type data module has the following properties:

Property Description

Trail

Sheets Per Trail The number of sheets, rotated around the length of the trail, to render for the trail.
Max Trail Count The number of live trails allowed.
Max Particle In Trail Count The maximum number of particles that the trail may contain at any one time.
Dead Trails On Deactivate If true, trails are marked dead when the ParticleSystem is deactivated. This means the trails will still render, but no new particles will be spawned, even if the ParticleSystem is re-activated.
Dead Trails On Source Loss If true, the trail is marked dead when the source of the trail is 'lost', i.e. the source particle dies.
Clip Source Segment If true, the trail will not be joined to the source position.
Enable Previous Tangent Recalculation If true, the previous tangent will be recalculated each time a new particle is spawned.
Tangent Recalculation Every Frame If true, all tangents are recalculated every frame to allow velocity/acceleration to be applied.
Spawn Initial Particle If true, the ribbon will spawn a particle when it first starts moving.
Render Axis The 'render' axis for the trail (what axis the trail is stretched out on). The following options are provided:
Option Description
Trails_CameraUp Traditional camera-facing trail.
Trails_SourceUp Use the up axis of the source for each spawned particle.
Trails_WorldUp Use the world up axis.

Spawn

Tangent Spawning Scalar The tangent scalar for spawning. Angles between tangent A and B are mapped to [0.0f .. 1.0f]. This is then multiplied by Tangent Spawning Scalar to give the number of particles to spawn.

Rendering

Render Geometry If true, the trail geometry will be rendered. This should typically be enabled as the trail is not visible otherwise.
Render Spawn Points If true, stars are rendered in the location of each spawned particle point along the trail. Used for debugging in Cascade.
Render Tangents If true, the tangent at each spawned particle point along the trail is rendered using a line. Used for debugging in Cascade.
Render Tessellation If true, the tessellated path between each spawned particle is rendered. Used for debugging in Cascade.
Tiling Distance The (estimated) covered distance to tile the 2nd UV set at. If 0.0, a second UV set will not be passed in.
Distance Tessellation Step Size The distance between tessellation points for the trail. This is used to determine how many tessellation points the trail has, and thus how smooth the trail is. The exact calculation is:
  TessellationPoints = TruncToInt((Distance Between Spawned Particles) / (DistanceTessellationStepSize))
Enable Tangent Diff Interp Scale

If this flag is enabled, the system will scale the number of interpolated vertices based on the difference in the tangents of neighboring particles. Each pair of neighboring particles will compute the following CheckTangent value:

If CheckTangent is < 0.5, then the DistanceTessellationStepSize will be scaled based on the result. 

This will map so that from parallel to orthogonal (0 to 90 degrees) will scale from 0 to 1. Anything greater than 90 degrees will clamp at a scale of 1.

Tangent Tessellation Scalar The tangent scalar for tessellation. Angles between tangent A and B are mapped to 0 to 1. This is then multiplied by TangentTessellationScalar to give the number of points to tessellate.
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