VEX-Snippets

Basic 3D Graphics Functions (Intersection / Nearest Distance / Projection)

Intersection Functions

I was trying to explore how intersections work in 3D graphics, so I made a collection of basic functions designed to find intersections in 3D space. These functions cover various intersection scenarios, including:

• Line-Line
• Segment-Segment
• Segment-Curve
• Line-Plane
• Plane-Plane
• Segment-Triangle
• Triangle-Triangle
• Segment-Planar Quad
• Segment-Bilinear Patch (both planar and non-planar quad)

Based on this research I developed the which improves precision of boolean fracturing as well as the node.

Nearest Distance (Geometric Tools)

This collection of functions is designed to find the nearest distances between various geometric entities.
Based on functions from Geometric Tools:

• dist_point_segment
• dist_segment_segment
• dist_line_line
• dist_line_segment
• dist_line_triangle
• dist_pt_triangle
• dist_segment_triangle
• dist_triangle_triangle

Projection

Projection simply involves finding the minimal distance. This can be achieved using Near Distance Functions (Geometric Tools Functions).

However, I found another implementations that might also be useful. These functions project a point onto: line, segment, plane, triangle, planar and non-planar quad.

, and

• Snippets for .
• Finding the (determine if a point is inside or outside 2D/3D geometry).
• direction between two primitives.
• :
  • primedges() – Get edges of a primitive.
  • pointedges() – Get edges connected to a point.
  • isedgeinprim() – Check if an edge belongs to a specific primitive.
  • edgeprims() – Find primitives that share an edge.
  • nearedgestopoint() – Find the nearest edge to a point.

• – Resamples a curve (similar to the Resample SOP but as a function).
• - Resample a curve while keeping certain points fixed (pinned).
• - Finds polyline connectivity based on constraint points, assigning different classes to segments at the Detail level.
• Finding points along a curve between UV coordinates.
• Finding nearby vertices based on UV coordinates.
• Finding a primitive line by two points.

HIPs

Solvecurve() / Solveik()

• demonstrating the use of solvecurve() and solveik() functions in VEX.
  
  
  

Nodes

Edge Preservation

Houdini’s basic nodes don't always preserve edge groups well during geometry operations. This collection of nodes is designed to handle geometry while maintaining edge groups.

These nodes were developed during the creation of my custom Boolean fracture system, which can be found in the repo.

• : More accurate edge group transfer compared to Transfer Groups.
  
• : Fuses points while keeping edge groups intact.
  
• : Remeshes geometry while transferring and preserving edge groups.
  
• : Copies edge groups, with an option to copy by ID.
  

Intersection and Shattering

These nodes were created to better understand intersection operations in Houdini.

• A custom version of the Intersection Analysis node, which can be slightly faster than the original. Like the original node, it can store @sourceprim, @sourceinput, and @sourceprimuv attributes. Additionally, it can split lines based on the primitives they belong to and store information about which edges points are associated with.
  
  

• : A basic version of a Boolean shatter node using Surface Mode. This node is a work in progress, and I'm continuing to improve it. It was developed as part of my exploration into creating something similar to a Boolean Shatter operation.

Handling Pieces

• : This node is essential for processing multiple pieces. It separates pieces from each other using their piece attribute, allowing you to iterate through them simultaneously. This is useful for tasks like generating captures between identical pieces, transferring attributes, or fusing by pieces. It is much faster than using a foreach loop or piece groups. This method is based on the "Point Deform" node.
  
  

• - generate bound for pieces

• - make Match Size for pieces

Useful for simulations

• : Removes jittering from animated points over time, especially useful for handling jittery simulations like cloth.
  
  

• Fuse Generate / Fuse Extract: A pair of nodes for fusing points and extracting values from the fused points.

  • : Fuses points and generates attributes for use with the Fuse Extract node.
  • : Extracts attributes from fused geometry and applies them to unfused geometry. These nodes are useful for simulations where geometry needs to be fused, such as simulating cloth or wires. After the simulation, the animated attributes are transferred back to the original unfused geometry.
    

Deformation and Skeleton Export

• : Converts rigid body animations into skeletal animations, allowing export in FBX format. This is useful for transferring RBD simulations into skeletal animations for game engines.

• : Converts deforming geometry into skeletal animations, exportable in FBX format. Ideal for simulations such as cloth or soft bodies, with support for tearing cloth from Vellum. It can handle multiple pieces and offers four capture methods.

• : Converts wire simulations from Vellum into skeletal animations for export in FBX format. Useful for wires, hair, string, and similar simulations. This node supports both intact and broken wires and works with multiple separate wires. Offers three capture methods.

• : Converts point capture data to bone capture data (@pCaptPts and @pCaptWeights to @boneCapture). This node allows to generate capture data between geometry and a skeleton using Point Deform, then convert it to bone capture deformation. Result will be work with the Bone Deform node.
  
  

• : Deforms geometry based on a spline, capable of handling multiple pieces. It uses primitive UVW and point deformation and has an OpenCL implementation for better performance.
  
  

Additional Nodes

• : Transfers UVs from one geometry to another. It's similar to the Labs UV Transfer node but much, much faster.
  
  
  
  

• : This node enhances Voronoi fracturing by using curves or planes as guides. It was developed during the search for a more precise solution to fracture geometry. While Voronoi fractures are accurate and stable, they often lack flexibility. This node makes the Voronoi fracture process more controllable.
  
  
  

• : A node for visualizing half-edges (hedges). It can generate visualizer markers to display hedge numbers.