spline force

 

 

This node will try to keep particles close to spline and make them move along by applying various forces. Depending on the parameters particles can follow the spline curve more or less strictly.

It accepts particles, positions of voxel grid as input.

 

[Inputs]

 

Particle Stream - This pin requires a particle stream to be connected. Connection is usually not required if any of the attributes is connected.

 

 

Enabled - Enable or disable node evaluation.

 

#Input (Position) - Calculate force at user defined position. Position can be retrieved from particles, voxels or any arbitraty point.

 

#Input (Grid) - Calculate force over the entire voxel grid. This operation is faster than applying force on a voxel-by-voxel basis.

 

Note: If Input (Position) is connected then the particle will not be moved by the force automatically. This is useful if user wants to do additional calculations by using the Force output value and does not want particle to be affected immediately.

 

#Spline Index - This input enables procedural spline selection for each particle. If there are multiple splines, particles are assigned to the closest spline. To assign splines randomly, use the Random node with a range from zero to the number of splines minus one. This option is available only for Particle and Position inputs.

 

Splines

Splines - Select NodeWorks splines you want particles to follow.

 

Shapes - Select 3ds max splines you want particles to follow. When multiple splines are used the closes spline to the particle will take control. Double click on object name to remove it from the list or use Remove button. You can select multiple objects.

 

Animated Shapes/Splines - Enable this option if splines are animated in any way. Keeping this option disabled results in faster computations.

 

Spline Lock - Enable this option to ensure particles follow the first spline curve they are assigned to. Without this, particles may switch splines based on proximity. This option is available only for Particle input.

 

Samples - In order to achieve faster calculations each spline is pre-sampled with user defined number of samples. Keep this number high if spline has many sharp curves as this will result is smoother and more accurate results.

 

 

Grid Properties

This rollout becomes available when voxel grid is connected to the Grid input.

 

Use CUDA ??? Enabling this option allows spline force calculations to be performed on the voxel grid using an NVIDIA GPU*, significantly accelerating computation. Depending on the scene complexity and hardware configuration, GPU-based processing can be up to six times faster compared to CPU execution. However, large voxel grids may exceed the available GPU memory, preventing force calculations from being processed on the GPU. In such cases, the system will skip computations.

Mode - There are two methods how to apply spline force to the voxel grid. In Force mode velocities will be added to the voxel grid. Velocity Blend mode will blend calculated velocities will be mixed with velocities inside the voxel grid.

 

Blend % - Amount of velocity blending. Value of 100% means that grid velocities will be completely replaced with calculated velocities.

 

Use Smoke - Enable this option is you want force to be computed only in voxels with smoke present.

 

Use Fire - Enable this option is you want force to be computed only in voxels with fire present.

 

Use Temperature - Enable this option is you want force to be computed only in voxels with temperature present.

 

Entire Grid - Enabling this option overrides all three previous options. Force will be calculated for all grid voxels regardless of the voxel content.

 

* CUDA Compute Capability 6.x (NVIDIA`s Pascal architecture) is a minimum.

 

 

PBD Liquid Properties

This rollout becomes available when PhysX simulation is connected to the PhysX input.

When the Spline Force node is used with PBD Liquids, its computation is exclusively executed on the GPU. This behavior is inherent to the system, as PBD Liquids rely entirely on GPU processing for simulation. Since all calculations related to PBD Liquids occur on the graphics card, the Spline Force node follows the same execution path to maintain computational efficiency and synchronization within the simulation framework.

 

PBD Phases List ??? The Spline Force node can be applied selectively to specific liquid phases. If no phase is specified, the force will affect all liquid phases by default.

 

Mode - There are two methods how to apply spline force to the voxel grid. In Force mode velocities will be added to the voxel grid. Velocity Blend mode will blend calculated velocities will be mixed with velocities inside the voxel grid.

 

Blend % - Amount of velocity blending. Value of 100% means that grid velocities will be completely replaced with calculated velocities.

 

Velocity Damping % - Reduces liquid particle velocity, helping them follow the spline more effectively under strong forces.

 

 

General Properties

Type - Choose the force application based on distance from the spline. The "Constant" option maintains a consistent force regardless of distance. "Falloff" dictates the distance range where force influence gradually diminishes. The "Range??? type defines the specific range within which force is active, excluding any particles or voxels outside this range from its effect.

 

Range Start - Distance at which the forces strength will fade until the distance reach the Falloff End.

 

Range End - Distance after which the forces do not exist and particles move freely.

 

Direction - Force along the spline that forces particles to follow the spline direction.

 

Direction Var % - Directional force variation.

 

Attraction - Force towards the spline. This value should be higher on shapes with lots of sharp turns and low on straight ones.

 

Attraction Var % - Attraction force variation.

 

Rotation - Force around the spline that forces particle to orbit the shape.

 

Rotation Var % - Rotational force variation.

 

Seed - Random number generator seed. Change this value to get different pattern.

 

 

[Outputs]

 

Force - For each input particle, position of voxel this pin will output the resulting force.

 

Relative Pos - Relative position along the spline where the force was calculated.

 

Influence - Output the spline influence based on the Falloff settings.