Implicit Surfaces

TL:DR Mathematical Shapes that can be animated, great for Colliders and Volume Domains as long as the shapes are simple-ish.

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implicit_surfaces.mp4

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Implicit surfaces do not fully support non-uniform scaling be mindful of it before using them SOP Implicit Surface Doctor can be used to try to fix it but it can adjust the shape own parameters.

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What is it?

SOP Main Nodes

SOP Implicit Surface: Creates Implicit Surfaces
SOP Implicit Surface Convert: Convert Implicit to VDB or Polygon
SOP Implicit Surface Operation: Boolean Operations

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To see the result of the Operation you need to preview it with a SOP Implicit Convert Output the the result to VDB or Mesh

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SOP Implicit Surface Slice: Inspect the Surface
SOP Implicit Surface Velocity: Computes @v and @w
SOP Implicit Surface Doctor: Fixes Non-uniform transforms

Implicit Surface Attributes

Stored as Point Attributes @surface - Float - Signed Distance, Negative Number: Inside the Surface, Positive Number: Outsside the Surface @grad - Vector - Direction Vector, similar to Volume Gradient, Similar to “Normals”. Useful for pushing points in/out. @shape - String - Shape name

VEX Usage

https://www.sidefx.com/docs/houdini/vex/functions/implicitsurface.html

https://www.sidefx.com/docs/houdini/vex/functions/implicitsurfacevel.html

Main Workflow

Reference Houdini Documentation

https://www.sidefx.com/docs/houdini/model/implicitsurfacesworkflow.html

https://www.sidefx.com/docs/houdini/model/implicitsurfacestechnical.html