public int getSortId() {
        int hash = 17;
        hash = hash * 23 + def.getSortId();
        hash = hash * 23 + paramDefines.hashCode();
        return hash;
    }
Compute the sort ID. Similar to {@link Object#hashCode()} but used
for sorting geometries for rendering.

@return the sort ID for this technique instance.
jme3-core/src/main/java/com/jme3/material/Technique.java