How to use VEX in the Gas field wrangle node to write that the surface tension (FLIP simulation) is zero if the position of the particles in Y is zero?

Hi,

If you bind the first input to Geometry, you can do it like this:

animatrix_
Hi,

If you bind the first input to Geometry, you can do it like this:

int pts [ ] = pcfind ( 0, "P", @P, 10, 1 );
vector p = point ( 0, "P", pts [ 0 ] );

float tolerance = 0.01;
if ( abs ( @P.y ) < tolerance )
    @surfacepressure = 0;

since "surfacepressure" is a float field instead of attribute, only last 3 lines are all it takes
no need to deal with particles at all or bind anything to Geometry a Gas Field Wrangle binds to fields by name automatically
however tolerance should be high enough to include voxel center positions of at least first few voxel layers from the ground to get noticeable effect

or if you want some falloff you can do this

The binding is to check for particle point positions which is what OP was asking.

I know surfacepressure is a field, that's why I am using a Gas Field Wrangle.

don't det me wrong, sampling the closest particle attributes to the current voxel may still be handy when basing surfacetension on different particle attributes, or alternatively rasterizing them to field first and sampling that

all I'm saying is that there is no need to care about particle positions in this case, since the surface tension is at voxel level and voxels have roughly the same position as average position of particles within that voxel
so I just assume that OP's description using particles just stems from assuming that it's particle based

animatrix_, tamte – many thanks for your help!