I must have missed a step, ‘cause my I3d file doesn’t animate.

First I set up an animated SOP system the end node of which is a MErge that combines all metaball systems into one. The SOP network has animated parameters. It animates from frame 1-192.

In SHOP I created VEX_Metacloud SHOP
In ROP created Image3D ROP
Set the frame range from 1-192
Set resolution to 128 128 128
Render As: Use meta/particle geometry
set Object and SOP correctly

Renered the i3d file

Created Vex 3D_Texture_Fog SHOP and and assigned it to read the i3d file. Created a non-rendering IsosurfaceSOP to preview the i3d file.

But the i3d is static, or appears to be.
When I scrub the timeline the isosurfaceSOP and rendered 3d fog do not animate as the source metaball surface does. It workls but for one frame.

The project is like this. The metaballSOP network is used to animate human embryo cells hoining and dividing. The i3d file is the volume swirls generator inside the metaballs.

Obviously I missed a step. So what do I need to do tog et to animate i3d.
DaveR

This has gotta be one of the more common mistakes that users make in Houdini.
My 2nd error is that I forgot that i3d is frame based format, for some reason I equeated with 3d version of Quicktime. I thought that 4d infor was stuffed into i3d file. Obviously not so