Hey,

I am trying to setup this ghostly echo effect. I used the trail sop to get delayed geo of the faces but I want to create and an attribute on the faces so that I can fade them in the render , so the most recent face will have opacity value of 1 and it will fade away.

With particles there is age but how can one do this with geo. I tried using the sop solver but it treats all the faces as one geo. Then I tried recreating the trails in the sop solver by offsetting the anim and merging with the previous frame but I still got stuck on the fading attribute.

Any suggestions .

Thanks

- store frame attribute on your geo:
f@frame = @Frame;

- append Trail SOP, each duplicate will have the frame attrib value according to the frame or subframe it was copied from

- compute the age based on the difference from current frame:
f@age = @Frame - f@frame;

The age attrib will be in frames starting with 0 at current frame, you can divide it by $FPS if you need it im seconds

Amazing, so simple and elegant. Thank you.