Houdini Bridge

The Houdini World Creator Bridge enables you to import your terrain creations seamlessly into Houdini, either as a Houdini heightfield for further processing or as a displaced grid for rendering.

Installation

Launch Houdini and navigate to the Assets menu to open the Install Asset Library panel. Here, locate the .hdanc file you extracted from the downloaded bridge file.

Ensure that you are using a Python3-based Houdini installation. The default build type for Houdini 19.0 and above should be this.

Parameters

• XML File

  Locate the .xml file for the desired sync project. For WC 22 and above, this file is located by default at [User]\Documents\World Creator\Sync\

• World Scale

  Sets the scale factor for the terrain.

• Height Scale

  Set the scale factor for the terrain's height.

• Output Type

  Choose the output type between heightfield for processing or displaced grid for rendering.

• Import Splat Layers to Heightfield

  Imports the splat layers from your World Creator materials as individual heightfield layers which can be helpful if you want them as masks for further processing in Houdini (only available for heightfields).

• Material

  Specify the renderer for which the materials need to be created.

• Import Material Layers

  Switch between using individual terrain layers or a baked color map in the generated material.

• Reset Materials

  Allows you to protect any changes made to specific material layers from the synchronization process. Note that this only works if you keep the original names!

• Force UV Scaling

  This scales the UVs of the grid slightly so that all height map wrapping artifacts should be invisible. This is applied to all octane terrains by default since it has a bug that prevents wrapping from being disabled.

The wc_bridge node must always be unlocked to function properly. This is because it internally creates material nodes in a matnet which can be generated only when it is unlocked.

Workflow Example

This example demonstrates how to render a terrain in Houdini using Octane. The Canyon sample file provided with World Creator will be used. The same steps can be applied to any other World Creator project.

Sync from World Creator

Select the Synchronise button in the application bar located at the top of the main panel to export all relevant data from World Creator automatically.

The World Creator scene before the sync

Sync into Houdini

Create a WC Bridge node within a geometry network. To enable Octane, set the Output Type to Grid and the Material to Octane, and click the Synchronize button.

Synced terrain in Houdini

Since we had Import Layers activated we now have individual submaterials for all material layers from World Creator, which can be further modified inside Houdini.

Note that the Octane bridge supports a maximum of 12 layers.

Let's give our terrain a winter look by changing the top sediment layer to snow to make it more visually appealing. To achieve this, obtain the Sediment diffuse material and insert a Tool_MixTexture node between the color map and the output, with white Color RGB as the color. Undoubtedly, creating the snow effect in World Creator could lead to a more precise outcome, but for the purpose of this guide, we will use Houdini.

Synced terrain with altered splat maps in Houdini

The landscape should resemble this now.

Using the bridge offers the significant advantage of faster iteration between World Creator and Houdini. To demonstrate this, set the seed of the entire terrain within World Creator to 1 in order to create a distinct scene that conforms to our original terrain design.

In order to maintain the snow cover changes in our Houdini material, disable the Reset Materials parameters in the bridge parameters. The bridge subsequently scans the terrain materials for pre-existing layers, retaining any modifications made to them while reloading any pertinent new textures. The sole prerequisite for this to function correctly is that you preserve the original names of the diffuse materials.

Although we are currently using this feature for a relatively simple modification, it can be used with more complex materials such as tri-planar shaders while maintaining the same iteration speed between World Creator and Houdini.

Material changes applied to a freshly imported terrain with a different seed

Sync into Houdini - Heightfield

In addition to importing our World Creator terrain as a regular mesh for rendering, we can also import it as a heightfield. To do this, modify the Output Type to Heightfield and optionally enable Import Splat Layers to Heightfield.

This will allow us to load individual materials from World Creator as heightfield layers for use in simulations.

The terrain imported into Houdini as a heightfield with its splat layers as heightfield layers