Brask

I remember that… No luck finding anything on the net so far, but in the mailing list archives I did find:
http://www.sidefx.com/community/interact/mailarchive/index.php?view=IDX&exactsubject=houdini%20contest&perpage=20&revdate=off [sidefx.com]
and:
http://www.sidefx.com/community/interact/mailarchive/index.php?view=IDX&exactsubject=SIG%2097&perpage=20&revdate=off [sidefx.com]

- Brask

The vm_surface attribute is added by the shader SOP. It contains the black magic to describe the shader to apply to each primitive.

The primitive meta weight option allows you to change the weight of metaballs. Put down a metaball sop, append a primitive with this option on, and you will see that you can change the weight with it.

- Brask

In Houdini the shading of polygons is determined by the point connectivity. If the vertices of two polygons share a point, they will shade smoothly. This is also used elsewhere, for example in the Subdivision and in the Triangle Strip methods.

This can be demonstrated with:
Box
Primitive.
Got to Attributes, change it to Add Color, set the fields to
1 $PR==0 1
You know have a purple cube with one white face on primitive 0.
Add a tristrip. You now have totally different colours as Houdini merged some of the side polygons with the white one. To avoid this, we have to tell Houdini that the primitives should not be connected in the tristrip.
Do this by, after the primitive, adding PrimitiveSplit. Set the attribute to Cd. Note that you now have unique points along the edge where the colours change.
Add a tristrip to this - it will match your original.

You can also use this to split the points where materials change by using vm_surface as the attribute name.

- Brask