metaimport

int  metaimport(int handle, string attrib, vector P, <type>&value)

<type>[] metaimport(string file, string attribute, vector P)

Rather than iterating over all the values, this form imports the values from all metaballs simultaneously. As with the scalar form, you can use the keywords…

• meta:density
• meta:prim
• meta:transform

…to import non-attribute information from the metaballs.

Once you get a handle to a metaball using metastart and metanext, you can query attributes of the metaball with metaimport.

There are three “special” attributes you can query:

float meta:density : The density of the current metaball

float meta:prim : The primitive number of the current metaball

matrix meta:transform : The transform associated with the current metaball. Applying the inverse of this transform will transform a point into the “space” of the metaball.

For example, the metaweight function can be expressed in the following way:

float
metaweight(string file; vector P)
{
int        handle;
float    density, tmp;

density = 0;
handle = metastart(file, P);
while (metanext(handle))
{
if (metaimport(handle, "meta:density", P, tmp))
density += tmp;
}
return density;
}

The attributes evaluated are un-premultiplied by the weight of the metaball at the position and must be multiplied for blending. For example, to evaluate a vector attribute (say color) on metaballs, the following function could be used:

vector
meta_attribute(string file, attrib_name; vector P)
{
int        handle;
vector    result, tmp;
float    density;

handle = metastart(file, P);
result = 0;
while (metanext(handle))
{
if (metaimport(handle, "meta:density", P, density))
{
if (metaimport(handle, attrib_name, P, tmp))
result += density * tmp;
}
return result;
}

In the i3d context, there is a default metaball geometry (specified by the -g option on the command line to the i3dgen program). If the filename is an empty string, the default geometry will be used.