> simulations

Nexus

simulations/nexus·v1.5.1

IN:3 OUT:3

SUMMARY

Nexus simulates the geometry on its first input using the constraint stream on its second, built by the Constraints operator and edited by Constraint Property. It solves stretch, bend, struts, glue, pins, attachments, pressure, shape matching and hair rods together with grain and fluid particles from a Particle Source, and outputs the simulated geometry, the constraints and the target geometry.

Self collision, a ground plane, a bounding box, a mesh or field collider, wind, drag, friction and a grabber act on every point, and adaptive substeps follow the fastest moments. The simulation runs as a feedback loop (Initialize, Start, Play) with a Target Feedback Loop POP for forces downstream, and its three outputs wire into Nexus Postprocess for welded seams, stress coloring, smoothing and guides.

PARAMETERS

PAGENexus

Target Feedback Loop POP	Targetpop	A reference to a POP node downstream in the network whose data is retrieved one frame later. P, PartVel and PartForce are read back.
Time Scale	Timescale	Speed multiplier on the time step. 0 freezes and 2 doubles.
Time Step	Timestep	The time step per frame in seconds, 1 divided by the cook rate (read-only). Time Scale multiplies it.
Substeps	Substeps	Number of solver substeps per 1/60 second. More substeps are more stable.
Iterations	Iterations	Number of constraint passes per substep.
Particle Substeps	Particlesubsteps	Sets the substeps of the grains and fluid, rounded to a divisor of Substeps. The constraints keep every substep. Fluids need at least 2.
Particle Iterations	Particleiterations	Sets the constraint iterations of the grains and fluid on each of their substeps. Fluids need at least 2.
Adaptive Substeps	Adaptivesubsteps	When on, the substep count follows the simulation between Min and Max Substeps. When off, the fixed Substeps are used.
Adapt Constraints	Adaptiveconstraints	When on, every point can raise the substep count, including cloth, hair and soft bodies. When off, only grains and fluid set it.
Min Substeps	Minsubsteps	Sets the fewest substeps per 1/60 second, more below 60 FPS. With Adapt Constraints on, set it to what cloth, hair and soft bodies need at rest.
Max Substeps	Maxsubsteps	Sets the most substeps per 1/60 second, more below 60 FPS, for the fastest moments.
CFL Condition	Cflcondition	Sets how far the fastest point may move per substep, in its own radii. Lower values run more substeps and tunnel less, higher values are cheaper.
Current Substeps	Currentsubsteps	Shows the number of substeps the solver runs this frame (read-only).
Initialize	Initializepulse	Initializes the POP from its input and parameters.
Start	Startpulse	Start the simulation from the initialized state.
Play	Play	Pause or play the feedback loop.
Step	Steppulse	Advance the simulation by one frame while paused.

PAGECollisions

Enable Self Collision	Enableselfcollision	Enable collisions of the surfaces with each other, and of grains and fluid with the meshes.
Collision Passes	Selfcollisionpasses	Number of self-collision solves per substep.
Stiffness	Selfstiffness	Fraction of each self-collision correction that is applied, from 0 to 1.
Enable Ground Collision	Enablegroundcollision	Collide with an infinite ground plane.
Display Ground	Displayground	Display the ground plane.
[+]Ground Position	Groundposition	A point on the ground plane.
[+]Ground Direction	Grounddirection	Normal of the ground plane. 0 1 0 is a level floor.
Ground Collision Margin	Groundmargin	Distance the points keep from the ground.
Enable Bounding Box Collision	Enablebboxcollision	Keep the points inside the bounding box.
Display Bounding Box	Displaybbox	Enable drawing the bounding box.
[+]Bounding Box Center	Bboxcenter	Center of the bounding box, in collider space.
[+]Bounding Box Size	Bboxsize	Size of the bounding box, in collider space.
Lower Bounds	Bboxlowerbounds	Enable the lower walls of the bounding box in each axis.
Upper Bounds	Bboxupperbounds	Enable the upper walls of the bounding box per axis.
Bounding Box Collision Margin	Bboxmargin	Distance the points keep from the box walls.
[+]Collision Type	Collisiontype	Selects the collider: none, a POP mesh (ray traced, Windows only) or a field used as an SDF volume.
Display Geometry	Displaygeo	Enable drawing the collider, as the mesh or the field's zero surface.
Collision Passes	Geocollisionpasses	Number of collider solves per substep. More passes hold fast moving geometry.
Collision POP	Collisionpop	The collider, either a mesh POP or an SDF field volume.
[+]Dist Attribute (SDF)	Distattr	For a field collider, the signed distance attribute of the Collision POP, negative inside.
Solid	Solid	When on, points inside the collider are pushed out. When off, the collider is hollow.
Keep Inside	Keepinside	When on, the collider is hollow and every outside point is pulled back in. When off, only escaping points are caught.
Project	Project	Place every point on the collider surface instead of colliding.
Collision Offset	Collisionoffset	Distance the points keep from the collider surface.
Collision Damping	Collisiondamping	Velocity lost on contact. 0 bounces and 1 stops.
[+]Transform Order	Xord	Sets the transform order of the collider and the bounding box.
[+]Rotate Order	Rord	Sets the order of the rotations of the collider and the bounding box.
[+]Translate	T	Translate the collider and the bounding box in the three axes.
[+]Rotate	R	Rotate the collider and the bounding box around the X, Y and Z axes. Angles are given in degrees.
[+]Scale	S	Scale factor for each axis of the collider and the bounding box.
[+]Pivot	P	The pivot point for the rotate and scale of the collider and the bounding box.
Uniform Scale	Scale	Specifies a uniform scale factor for the collider and the bounding box.
[+]Display Color	Displaycolor	Sets the color of the displayed guides.

PAGEForces

[+]Gravity	Gravity	The gravity vector in units per second squared.
Gravity Multiplier	Gravitymultiplier	Multiplies the Gravity vector.
[+]Wind Direction	Winddirection	The direction the wind blows in. Its length does not matter.
Wind Speed	Windspeed	The wind acceleration along Wind Direction, in units per second squared.
Velocity Damping	Velocitydamping	Amount of damping applied to the velocity. 0 applies no damping.
Normal Drag	Normaldrag	Air drag across the surface where the geometry carries no DragNormal. The velocity along the normal decays at this rate per second.
Tangent Drag	Tangentdrag	Air drag along the surface where the geometry carries no DragTangent.
Static Threshold	Staticthreshold	Sets the static friction coefficient. Contacts below it grip.
Dynamic Scale	Dynamicscale	Sets the kinetic friction coefficient that slows sliding contacts.
Enable Self	Enableself	Enable friction on the self-collision contacts.
Enable External	Enableexternal	Enable friction on the bounding box, the Collision POP and fields. The ground always uses its own friction.
Ground Static Scale	Groundstaticscale	Sets the static friction of the ground plane. 0 is frictionless.
Ground Dynamic Scale	Grounddynamicscale	Sets the kinetic friction of the ground plane.
Enable Grabber	Enablegrabber	Enable the grabber: grab and drag the simulated points inside a sphere.
Grab	Grab	While on, the points inside the grabber when it turned on follow Position.
[+]Position	Grabposition	Sets the position of the grabber in world space.
[+]Radius	Grabradius	Sets the radius of the grabber sphere on each axis.
Strength	Grabstrength	Determines how firmly the grabbed points follow. 1 holds them like pins, lower values let the simulation pull them.
Transition Range	Transitionrange	Width of the falloff at the edge of the grabber sphere.
Transition Align	Transitionalign	Moves the falloff inside (-0.5) or outside (0.5) the sphere edge.
[+]Transition Type	Transitiontype	Determines the interpolation curve of the falloff.
Display Grabber	Displaygrabber	Display the grabber sphere in the viewport.
Visualize Grabbed Points	Visgrabbedpoints	Color the points the grabber holds (or would take) red.

PAGEAdvanced

[+]Integration Order	Integrationorder	Sets the integration order of the position update.
Enable Max Acceleration	Enablemaxacc	Limit the acceleration to Max Acceleration.
Max Acceleration	Maxacceleration	Sets the maximum acceleration magnitude.
Limit Acceleration in Velocity Update	Limitaccel	When on, the acceleration limit applies to the velocity update instead of the position step.
Fallback to First Order Integration on Collision	Fallbackcollision	Use first order integration on collision, which is more stable.
Relaxation	Relaxation	Scales each constraint step. 1 is exact, below 1 is softer, above 1 is stiffer but jittery.
Self Step Clamp	Selfclampscale	Limits the move per substep to this fraction of the contact diameter, which prevents tunneling.
Rest Exclude Scale	Restexcludescale	Skips self-collision pairs that are closer at rest than this multiple of the contact distance.
Search Scale	Searchscale	Sets the neighbor search range as a multiple of the contact distance, used for the particle contacts and attraction.
Max Neighbors	Maxneighbors	Maximum number of neighbors each particle considers per substep. Fewer is faster, too few lets particles overlap.
Repulsion Weight	Repulsionweight	Sets the strength of the particle contacts. 1 resolves the overlap in each iteration.
Attraction Weight	Attractionweight	Sets the strength of the pull between grains that are slightly apart, for clumping materials like wet sand. Does not apply to fluid.
Kernel Radius Scale	Kernelradiusscale	Sets the radius of the fluid kernel in particle radii. Larger values give a smoother fluid and bigger drops but are slower.
Viscosity	Fluidviscosity	Determines how much each fluid particle's velocity moves toward its neighbors' every substep. 0.01 is like water, 1 is nearly rigid.
Surface Tension	Surfacetension	Cohesion between fluid particles of the same phase. Forms drops and a surface skin.
Adhesion	Adhesion	Sets how strongly the fluid clings to solid particles, the ground, the bounding box and colliders.
Relaxation Epsilon	Relaxationepsilon	Softens the fluid density constraint. Higher values are softer and more stable.
Unilateral Density	Unilateraldensity	When on, the fluid density only pushes particles apart, which prevents clumping. When off, Anti-Clumping applies.
Anti-Clumping	Anticlumping	When Unilateral Density is off, keeps fluid particles from clumping into strings and clusters. 0 turns it off.

PAGECommon

Free Extra GPU Memory

Freeextragpumem

Free memory that has accumulated when output memory has grown and shrunk.

INPUTS

Input 0 POP - Geometry

Input 1 POP - Constraints

Input 2 POP - Target Geometry

OUTPUTS

Output 0 POP - Geometry

Output 1 POP - Constraints

Output 2 POP - Target Geometry