Pyro spread using custom velocity and the strange behaviour when I increase Acceleration Strength

[pixel_wizard]

Hello

Im starting to learn how to create my own custom velocity in pyro. I have this desired effect where the smoke is spreading outward from the center. I set up vector attributes on pyro source points, convert them using volume from attributes and set the Vel source to 'pull' the source volume. at first everything works fine and dandy and I have a the smoke being advected outwards from the center.

[pixel_wizard]

However when I go to increase the Acceleration strength in the pull opperation I ends up pulling it predominantly in +x +y cordinates. I cant figure out for the life of me why this is happening. I want to use the Acceration and Decelaration to adjust the effect but it seems to give me this strange result

Edited October 3, 2023 by pixel_wizard

[pixel_wizard]

For convenience ive attached my working file below

CustomVelocity.hipnc

[Librarian]

@pixel_wizard If you play with this Ex ...Just adapt to yours Ex. Maybe it gonna Help to understand. Velocity filed and P'scale (try to change diff rules in rasterize) .
 

Pscale.hiplc

[pixel_wizard]

Thank you! ill have a dig around setup

[Atom]

If you read the help card, you'll find that the PULL mode mixes Acceleration, Deceleration, and Direction to achieve its goal. By default, Direction is disabled. My guess, supplying a null vector which produces the direction anomaly you're experiencing. Try enabling Direction and setting all three values to the same number. This produces the expected uniform expansion.