Purpose

SDF Collider turns a mesh or analytic primitive into a signed distance field. Solvers sample its distance to push points out of obstacles or keep them inside a domain. The output also includes a transform set for the collider’s fitted pose.

Use

Place SDF Collider in the Geometry view, under Solvers. For a first obstacle, choose Analytic Primitive, select Sphere and start with Radius at 0.5 and Resolution at 48. Place it where the receiving solver’s particles will reach it.

On the receiving solver’s Resources page, add a Connections row, select its sdf input in Type and choose this collider’s field resource. Select the xform output in a separate xforms row when the receiver uses moving-collider transforms. Check the row Status after selecting each resource.

Inputs and outputs

Geometry Input reads the incoming mesh. Analytic Primitive uses the shape controls without a mesh; Blend Geometry + Primitive combines them. The outputs are field0, the collision field, and xform, the fitted transforms.

Input SDF appears in the Source menu, but the current public declaration has no SDF input port. Use the mesh or primitive modes for this node’s documented connection workflow.

Controls

• Primitive chooses Box, Sphere, Cylinder, Capsule, Plane, Torus or Rounded Box. Center, Size, Rotation and the relevant radius controls place and shape it.
• Domain Mode chooses solid inside or free inside. Invert Sign reverses the sign; use it deliberately, since it changes which side the solver treats as solid.
• Dilate, Erode and Offset move the collision boundary. Smooth and Blend Width modify the field and the geometry/primitive blend.
• Resolution sets the cubic field density. Padding adds room around the mesh bounds. Max Triangles caps mesh capacity; begin with a simple mesh before increasing it.
• Geometry Pose chooses Fit Rigid Pose or AABB Only. Surface Slip ranges from no slip at 0 to full slip at 1 for consumers that use it.
• Rebuild Field refreshes the field. Structural edits follow Auto-Rebuild or wait for Rebuild. Show Preview and its density and length controls change the field display.

Notes

Animated mesh input can update the field, including changing point counts. Do not assume animation only changes a transform or that a deforming mesh costs the same as an analytic primitive.

Thin features need enough field resolution to survive sampling. For mesh input, use a closed surface with a clear inside and outside; the Hybrid and Winding number sign methods depend on that distinction.

Ports

Inputs

• geometry points

Outputs

• field0 sdf collider
• xform transforms
• preview lines
• preview_cd lines

Parameters

SDF Collider

Auto-Rebuild on Build Params (Autorebuild) Toggle op('sdf_collider').par.Autorebuild

Default:

On

Options:

Off, On

Rebuild (Rebuildnow) Pulse op('sdf_collider').par.Rebuildnow

Default:

None

Simulate (Simulate) Toggle op('sdf_collider').par.Simulate

Default:

On

Options:

Off, On

Reset (Resetsolver) Pulse op('sdf_collider').par.Resetsolver

Default:

None

Preview

Show Preview (Previewshow) Toggle op('sdf_collider').par.Previewshow

Default:

On

Options:

Off, On

Preview Density (Previewdensity) Int op('sdf_collider').par.Previewdensity

Default:

12

Range:

2 to 48

Preview Length (cells) (Previewlength) Float op('sdf_collider').par.Previewlength

Default:

0.6

Range:

0 to 2

Outputs

SDF Collider Resource (Hdrsdfout) Str op('sdf_collider').par.Hdrsdfout

Read only.

Default:

"" (Empty String)

Collider Output Resource (Resourcename) Str op('sdf_collider').par.Resourcename

Default:

collider

Source

SDF Source (Hdrsource) Str op('sdf_collider').par.Hdrsource

Read only.

Default:

"" (Empty String)

Source (Source) Menu op('sdf_collider').par.Source

Default:

0

Options:

Geometry Input, Analytic Primitive, Input SDF, Blend Geometry + Primitive

Geometry Pose (Posefit) Menu op('sdf_collider').par.Posefit

Default:

0

Options:

Fit Rigid Pose, AABB Only

Primitive (Primitive) Menu op('sdf_collider').par.Primitive

Default:

0

Options:

Box, Sphere, Cylinder, Capsule, Plane, Torus, Rounded Box

Center (Centerx) Float op('sdf_collider').par.Centerx

Default:

0

Range:

-1000 to 1000

Center Y (Centery) Float op('sdf_collider').par.Centery

Default:

0

Range:

-1000 to 1000

Center Z (Centerz) Float op('sdf_collider').par.Centerz

Default:

0

Range:

-1000 to 1000

Size (Sizex) Float op('sdf_collider').par.Sizex

Default:

1

Range:

0.0001 to 1000

Size Y (Sizey) Float op('sdf_collider').par.Sizey

Default:

1

Range:

0.0001 to 1000

Size Z (Sizez) Float op('sdf_collider').par.Sizez

Default:

1

Range:

0.0001 to 1000

Rotation (deg) (Rotationx) Float op('sdf_collider').par.Rotationx

Default:

0

Range:

-360 to 360

Rotation (deg) Y (Rotationy) Float op('sdf_collider').par.Rotationy

Default:

0

Range:

-360 to 360

Rotation (deg) Z (Rotationz) Float op('sdf_collider').par.Rotationz

Default:

0

Range:

-360 to 360

Radius (Radius) Float op('sdf_collider').par.Radius

Default:

0.5

Range:

0.0001 to 1000

Minor Radius (Radius2) Float op('sdf_collider').par.Radius2

Default:

0.125

Range:

0.0001 to 1000

Height (Height) Float op('sdf_collider').par.Height

Default:

1

Range:

0.0001 to 1000

Round Radius (Round) Float op('sdf_collider').par.Round

Default:

0

Range:

0 to 1000

Domain

Domain / Sign (Hdrdomain) Str op('sdf_collider').par.Hdrdomain

Read only.

Default:

"" (Empty String)

Domain Mode (Domainmode) Menu op('sdf_collider').par.Domainmode

Default:

0

Options:

Collider (solid inside), Domain (free inside)

Invert Sign (Invert) Toggle op('sdf_collider').par.Invert

Default:

Off

Options:

Off, On

Dilate (Dilate) Float op('sdf_collider').par.Dilate

Default:

0

Range:

0 to 1000

Erode (Erode) Float op('sdf_collider').par.Erode

Default:

0

Range:

0 to 1000

Offset (Offset) Float op('sdf_collider').par.Offset

Default:

0

Range:

-1000 to 1000

Smooth (Smooth) Float op('sdf_collider').par.Smooth

Default:

0

Range:

0 to 1000

Blend Width (Blend) Float op('sdf_collider').par.Blend

Default:

0

Range:

0 to 1000

Surface Slip (0=no-slip 1=full-slip) (Surfaceslip) Float op('sdf_collider').par.Surfaceslip

Default:

0

Range:

0 to 1

Field

Field Build (Hdrfield) Str op('sdf_collider').par.Hdrfield

Read only.

Default:

"" (Empty String)

Resolution (N^3) (Resolution) Int op('sdf_collider').par.Resolution

Default:

48

Range:

8 to 128

Padding (frac of bbox diag) (Padding) Float op('sdf_collider').par.Padding

Default:

0.1

Range:

0 to 1

Max Triangles (ceiling) (Maxtriangles) Int op('sdf_collider').par.Maxtriangles

Default:

200000

Range:

1000 to 2000000

Sign Method (Method) Menu op('sdf_collider').par.Method

Default:

0

Options:

Hybrid (ray + winding), Winding number

Triangle AABB Margin (Boxmargin) Float op('sdf_collider').par.Boxmargin

Default:

0.00001

Range:

0 to 1

Rebuild Field (Rebuild) Pulse op('sdf_collider').par.Rebuild

Default:

None