Image 3D Files

1. At the Output level in the network editor, use the tab menu to create a 3D Texture Generator output driver.

2. At the SHOP level in the network editor, use the tab menu to create a VEX Fluffy Clouds shader. This is an image3d shader that will be used to fill in the data in the new .i3d file.

3. Assign the new shader to the SHOP parameter in the parameter editor of the output driver.

4. Render the .i3d file.

   The file should be generated on disk in the directory where you started Houdini and will be called “cloud.i3d”. To visualize the I3D file as an isosurface, you can load it in using the Isosurface node.

Once you have generated an i3d file, you can render it using the Mantra: Image3D Volume Procedural.

The following are ways of creating I3D files:

• The i3dgen program.

  A stand alone tool which runs VEX to create a .i3d file.

• The 3D Texture Generator output driver.

  An interface into i3dgen from within Houdini. This facilitates using VOPs to generate I3D files.

• The geo2i3d output driver.

  Uses a VOP network to convert a volume primitive into an I3D file.

• Mantra supports direct rendering of I3D files as volumes.

  • Mantra: Image3D Procedural

  • Mantra: Image3D Volume Procedural

• There are some old-style Image3D shaders available.

  • VEX Fluffy Clouds

  • VEX Meta Cloud

  • VEX 3D Texture Fog

  • VEX Image3D SHOP

• In VOPs, 3d textures can be accessed using the texture3d vex function. It allows 3d textures to be used in compositing, SOPs, particle simulations, as well as other places where VEX is used.

Compositing I3D files can be done easily in VOPs. For example, you can add two textures together by using the texture3d VOP to read the values and sum the results. The composited result can be used to generate a new I3D file in an image3d SHOP. It can also be used to adjust the velocity of a particle in a POP.