bifrost accelrator direction (use object's transform)

We need to create a relationship between the emitter’s rotation

and its Acceleration Direction vector.To do this, we'll use a pointMatrixMult node.This node allows us to multiply a point by a matrix.Rename it "water_spray_redirect_MULT".First, we'll feed the emitter shape node's "worldMatrix" attributeinto this node's "In Matrix" attribute.The worldMatrix attribute represents the 4 x 4 transformation matrixof the emitter's translation and rotation in World Space.As the emitter moves along with the gun, this vector changes accordingly.Next, we need to multiply this vector by the emitter’s spray direction attribute,which is in its own local space.Remember that our starting direction vector in world space was -1, 0.577, 0.However, relative to the emitting cylinder object, it's simply spraying straight out the top.Thus, we'll set In Point to 0, 1, 0.We'll also need to turn on Vector Multiply to specify that we want a vector productrather than the scalar product.Now you can feed the output of this into the water_spray_emitter_GEOShape's"Bifrost Accelerator Direction" attribute.

caching bifrost foam

FROM CGTALK

I think I figured it out. 

This is the process:

1. get liquid looking how you'd like
2. cache liquid (default cache control: 1)

3. select container -> add foam

4. get foam looking how you'd like

5. check 'Enable' in Foam Cache tab -> Cache Control set to 2
6. run timeline for length of cache

7. Change Cache Control to 3

Voila! The problem before was that I went to the BiFrost menu bar and tried to recache everything - and Maya was asking if I wanted to replace or rename existing cache - neither of which I wanted to do.

bifrost foam particle size

mel script to set render size of foam particles in Maya Bifrost
set display to points..

setAttr foamShape1.renderParticleSize .01;