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The Trail op takes an input op and makes a trail of each point of the input op over the past several frames, and connects the trails in different ways. It will generate trails of any input geometry, whether it is a cube translating, a deforming surface, or particles. This is useful for multi-frame ghosting effects and temporal modeling.
The particles thrown off the end-most points receive a higher velocity than those close to the root of the L-system (enable Points display in Viewport Display):
Temporal modeling with the Trail op: the corners of a translated and rotated cube are used as a source for the Trail op with a Trail Length of 50 frames connected by Columns.
How to construct the trail geometry.
Number of frames in trail.
Number of frames to skip in trail.
Number of frames to cache in RAM.
Resets the cache memory buffer.
Evaluate Within Frame Range
Clamp evaluation between
$FEND, otherwise may
evaluate before start frame.
How to create the output mesh.
Closes the rows in the output mesh.
When computing velocity the resulting velocity will be scaled by this
constant. Note there is an internal scale of
$FPS to convert the
measured change over a frame into a change over a second.
This is the method that is used to approximate the velocity from the point positions.
You can choose between Backward Difference, Central Difference and Forward Difference. Generally, Central Difference gives more accurate results.
When computing velocity, you can optionally also approximate acceleration by enabling this option.
The calculated accelerations will only be non-zero if Velocity Approximation is set to Central Difference.
The computed acceleration will be stored in this attribute.
Compute Angular Velocity
The difference in orientation of successive frames will be used to
compute an angular velocity,
w, for the points.
N attribute is needed to compute angular velocity. Without
N, the angular velocities are all zero.
Match by Attribute
Points on successive frames will be identified by using the provided integer attribute rather than the point number.
Attribute to Match
The name of the integer or string point attribute to use for matching successive frames.
The following examples include this node.
This example shows how a piece of cloth that is pinned on four corners. These corners are constrained to the animated geometry.
This cloth example demonstrates the Friction parameter on the Physical properties of a cloth object.
This is an example that shows how you can specify the warped and weft directions on a triangulated cloth planel using uv coordinates.
Because the uv directions are aligned with the xy directions of the grid, the result looks nearly identical to a quad grid, even though the mesh is triangulated.
The little blue and yellow lines visualize the directions of the cloth fabric. This is enabled in the Visualization tab of both cloth objects.
This example shows a pieces of cloth with different properties colliding with spheres. By adjusting the stiffness, bend, and surfacemassdensity values, we can give the cloth a variety of different behaviours.
This example demonstraits a paneling workflow to create a open-ended rectangular prism which keeps its shape.
This example demonstraits a paneling workflow and use of the seamangle primitive attribute to create a cloth ruffle attached to a static object.
This example shows how to create a basic constraint network with point anchors.
This scene shows how to create FLIP fluids based on the velocity of geometry by generating new particles from points scattered on the original geometry based on the velocity vectors. It also shows how to set up the original geometry to act as a collision object for the fluid.
This example simulates grass being pushed down by an RBD object. Fur Objects are used to represent the blades of grass and Wire Objects are used to simulate the motion. When a single Fur Object is used to represent the grass, neighbouring blades of grass will have similar motion. Additional objects with different stiffness values can be used to make the motion less uniform. When "Complex Mode" is enabled, two objects are used to represent the grass. The stiffness of each set of curves can be controlled by adjusting the "Angular Spring Constant" and "Linear Spring Constant" parameters on the corresponding Wire Objects.
This example demonstrates the how the shatter, RBD Fractured Object, and Debris shelf tools can be used to create debris emanating from fractured pieces of geometry.
First, the Shatter tool (from the Model tool shelf) is used on the glass to define the fractures. Then the RBD Fracture tool is used on the glass to create RBD objects out of the fractured pieces. Then the Debris tool is used on the RBD fractured objects to create debris.
This example demonstrates the use of the RBD State node to inherit velocity from movement and collision with other objects in a glued RBD fracture simulation.
This solid object has a strong volume-preserving force (e.g. flesh). The effect of the volume-preserving force is clearly visible when the object hits the ground plane.
The Copy SOP is used to copy geometry to particles using the Particle SOP as a template. In the example, the Scale parameter of the Copy SOP is used to create the specific effect. The Copy SOP may also be used to control different attributes of the copied geometry beyond mere scale.
Play the animation to see the effects.