Controlling flip particles scale with point sop

[cgvfx]

Hi Everyone,

                     I did a flip sim and cached it in bgeo.NOw i want to render those particles,but the problem is in my shot camera is moving,from far particles scale seems to be ok but when it comes closer to the camera,particles looking very big,how do i control the scale of the partilces, i want to animate the scale or any other option is there.I m rendering the particles through volume shader.

 

Thanks

[pbarua]

Shelf tool puts down a pointwrangle after import_whitewater.

In wrangle you have:

// Post-simulation tweaks
@pscale *= 1;
@v *= 1;

change @pscale value how you like.

[cgvfx]

Hi Pradeep,

                     Thanks for a quick response.So, i can tweak the radius with wrangle but if i just want to animate the radius,i dont want the particles to actually die.Particles size should gradually decrease while coming closer to the camera.Is there any way i can animate or a small expression will do.

 

Sry! for the dual post.

 

Thanks

[pbarua]

Add a spare parameter then channel reference it in wrangle.

Something like this:

// Post-simulation tweaks
@pscale *= ch("scalemult"); //where scalemult is spare parameter 
@v *= 1;

where scalemult is spare parameter.

You can animate this parameter.

[old school]

Common technique is to use a UV Texture SOP in camera mode. Reference your camera and voila, you now have uvw 3D co-ordinates wrt your chosen camera. You can access the uvw components with $MAPU, $MAPV and $MAPW in SOP parameter expressions, in any wringer as @uv.x @uv.y and @uv.z and in VOPs, place a Bind SOP to fetch vector type named "uv".

 

The third component is the distance of each given point from the camera's position point of view. That is what you can use to modulate your pscale attribute.

[cgvfx]

Thanks Pradeep and Grand Master,its working fine.