pscale change not visible in render

[haggi]

If I create a simple particle system and add an attribute called pscale I can modify the size of the points in rendering.

Now if I modify this attribute in a pop network, the value is not visible in rendering until I go to a new frame.

If I add this attribute at the geometry level, the modification of the pscale value is immedialty visible in a rendering.

So I suppose there is some caching behaviour for the current frame. Is there a way to do a re-evaluation of the current particle system

without goin to the next frame every time so that I can see my modification?

[SpencerL]

If I create a simple particle system and add an attribute called pscale I can modify the size of the points in rendering.

Now if I modify this attribute in a pop network, the value is not visible in rendering until I go to a new frame.

If I add this attribute at the geometry level, the modification of the pscale value is immedialty visible in a rendering.

So I suppose there is some caching behaviour for the current frame. Is there a way to do a re-evaluation of the current particle system

without goin to the next frame every time so that I can see my modification?

Because its a simulation, if you make any changes in your pop network you will need to rewind back to frame 1 in order to see their effect.

[haggi]

Because its a simulation, if you make any changes in your pop network you will need to rewind back to frame 1 in order to see their effect.

You are right, in maya it is the same... stupid me.

[old school]

To force re-evaluation of a particle system when you change a value not at the start frame, you can RMB on the brain and choose Reset All Simulations or select the specific sim from the list below that option.

Btw you should notice the brain go "red" when you have invalidated the sim by tweaking a value.

As an aside you figured out you can post-massage any attribute on any geometry. Modifying pscale with a Point SOP > Particle folder > Scale parameter is very common. You also have access to $AGE, $LIFE and other particle point attributes.

Some common functions:

$PSCALE * 0.5

Cuts the scale down in half

fit($PSCALE, 0, 1, 0.2, 0.8)

remaps the pscale attribute to a new fit range.

smooth($AGE, 0, 2) * $PSCALE

will scale up the instance geometry from 0 to $PSCALE according to the age of each particle.

(smooth($AGE, 0, 2) - smooth($AGE, 4, 6)) * $PSCLAE

will ease in the scale between age 0 to 2 then scale them back down to 0 from age 4 to 6.

$PSCALE * fit(length($VX, $VY, $VZ), 0, 10, 0, 1.25)

will increase the psacle as the particles move faster.