by Dušan Cvetković
Dušan Cvetković
Published February 1, 2021

Rhino 7 introduces powerful new SubD modeling components in Grasshopper. SubD modeling combines the smooth surfaces of subdivision surfaces with the control of polygonal meshes. In this complete guide, we will explore how to leverage Grasshopper's SubD components to create, edit, and convert SubD geometry.

An Overview of SubD Grasshopper Components

SubD Grasshopper components are located in the Surfaces tab under the SubD panel. The key components are:

  • SubD From Mesh - Converts a mesh into a SubD surface
  • Mesh From SubD - Converts a SubD into a mesh
  • SubD From Edges - Extracts edges and edge information from a SubD
  • SubD Control Polygon - Displays the control polygon of a SubD
  • SubD Fuse - Joins and boolean operations on SubD objects

By combining these tools, you gain precise control over creating, manipulating, and converting SubD geometry.

Converting a Mesh into a Smooth SubD Surface

A common workflow is converting a polygonal mesh into a smooth SubD surface. The SubD From Mesh component makes this easy.

To demonstrate, we'll start with a mesh consisting of multiple surface pieces. First, we need to weld the mesh faces together into a single closed polysurface.

The SubD From Mesh component has inputs for setting edge creases, corner sharpness, and mesh interpolation. Setting the crease to 2 will crease the naked edges in the original mesh. Setting corners to 2 will sharpen corners.

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The result is a high-quality SubD surface matching the shape of our original mesh. By controlling creases and corners, we maintain crisp edges in the SubD model.

Analyzing and Extracting SubD Edge Information

The SubD From Edges component extracts edge curves and data from a SubD model. The T output contains textual information identifying each edge type and attribute.

We can use this data to filter and select specific edges. For example, to find all crease edges we can:

  • Search edge data for the word "crease"
  • Use the found pattern to filter the edge curves
  • Extract only the crease edge curves

This component gives us precise control over selecting and working with edges based on their SubD properties.

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Converting a SubD Back into a Mesh

The Mesh From SubD component converts a SubD surface back into a polygonal mesh. The density input controls how many subdivisions are used in the mesh.

Higher densities result in smoother meshes and better approximation of the smooth SubD shape. This can be useful for converting SubD geometry into a mesh for manufacturing or analysis.

Visualizing the SubD Control Polygon

The SubD Control Polygon component displays the low-poly control cage of a SubD surface. This control cage forms the basis of the SubD shape.

Visualizing the control polygon helps understand the underlying structure of a SubD model. It also facilitates editing the control cage to manipulate the shape.

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Combining SubD Objects with SubD Fuse

The SubD Fuse component joins multiple SubD objects into one combined SubD result. This is useful for assembling SubD geometry from separate pieces.

SubD Fuse performs boolean union, intersection, difference, and combining operations. If the SubDs don't initially touch, they can first be converted to meshes before fusing.

By leveraging these SubD Grasshopper components, complex models can be built up from smaller SubD building blocks.

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Key Takeaways

SubD Grasshopper components open up efficient workflows for controlled SubD modeling:

  • Convert meshes into smooth SubD surfaces with crease control
  • Analyze and extract SubD edge information for advanced editing
  • Convert SubD geometry back into polygonal meshes
  • Visualize and edit the SubD control cage
  • Combine SubD objects together with boolean operations

SubD modeling combines freeform modeling with precision control - making it ideal for product design, manufacturing, and more. By harnessing Grasshopper's SubD tools you gain immense flexibility and power over creating, editing, and converting SubD geometry.

More Resources

To dive deeper into SubD modeling in Grasshopper, you can check out the extended tutorial on our Patreon page.

Start leveraging SubD components in Grasshopper today to take your designs to the next level! Let us know if you have any other questions.

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About the Author

Dušan Cvetković is a professional architect from Serbia with international experience in the industry. Collaborated with numerous clients all around the world in the field of architecture design, 3D modeling and software education. He's been teaching Rhinoceros3D to thousands of architects through How to Rhino community and various social media channels.