Houdini 11 How to

  • SDFs as volume primitives can live in .bgeo files. They show up in the viewport as sort of inverted because the default fog makes the outside areas opaque. However, you can use the Primitive SOP to set their visualization to Iso Surface.

  • .sim stores a bunch of simulation objects and their attached data. .simdata only stores the data attached to some simulation object.

  • You can create SDFs in .sim format and save them as .simdata. It is a mostly DOP specific format, but the File SOP will read .sim and .simdata.

  • The Isooffset SOP only saves .simdata files. The File DOP saves .sim files. The File Data DOP saves .simdata files. The Explicit Cache option on the DOP Network saves .sim files. The Dynamics output driver saves .sim files.

  • Isooffset reads .simdata, not .sim. The File SOP will read .sim and .simdata.

  • There is the Dynamics ROP to create .sim.

  • The File SOP can be used directly to read an SDF from within a .sim being referenced by a DOP Import SOP. If you specify a .sim, it unlocks the object mask and data path to read from.

  • To turn an SDF into a .sim, Volume Sample it in an Isooffset SOP and use the write mode. This will create a .simdata, suitable for use by the RBD Collision cache.