solver transfer attribute, eg. colour accumulation

i always have to look this up on cgwiki...

the left stream is some sweat drops falling down a surface.. the right stream is the surface. 

It goes into a solver

The slight 0.0075 blend in the blendshape causes a slight fade of the attribute being transferred. Leaving it at zero will result in an absolute solver-accumulation of the value.

multiple colour sets on alembics, for Maya

This probably contradicts something I've written before, but you CAN export multiple colour sets in Houdini, for alembicking. The key is in the attribute creation. Make sure you use an explicit attribute create node, specify a float, of colour type. Oh and make sure it's on the vertices, because Maya. It will now show up along trusty ol' Cd in Maya's Color Set Manager.

set colour according to bounding box.

now that the old Point node is more or less dead and buried, we have to rely on wrangles or vops to set our colours in fancy ways.

To give an object a gradient of colour based on it's bounding box (eg. black-to-red, from -ve to +ve on the x axis) we can use the relbbox function.
In a wrangle, we can type

@Cd=set(relbbox(@P.x),0,0);

tadah!