int [] primfind(<geometry>geometry, vector min, vector max)
Find all the primitives whose bounding boxes overlap the given box.
int [] primfind(<geometry>geometry, string group, vector min, vector max)
Find all primitives in a group whose bounding boxes overlap the given box.
<geometry>
При запуске в контексте ноды (например, Wrangle SOP) этот аргумент может быть целым числом, представляющим номер входа (начиная с 0), с которого функция будет читать атрибуты.
В качестве альтернативы аргумент может быть строкой, указывающей на файл геометрии (например, *.bgeo) для чтения. При запуске внутри Houdini может быть ссылкой op:/путь/до/sop.
min, max
These vectors define the minimum and maximum corners of the bounding box to search.
group
If given, only match primitives in this group.
An empty group string will include all primitives.
The string supports Ad-hoc patterns like 0-10 and @Cd.x>0.
Returns
An array of primitive numbers.
Note
These functions are intended to be used as an optimization to finding primitives
in a particular area for processing. For instance, to find all the curves
from one input intersecting polygons on another input, we may naively iterate
over all polygons for each curve to determine their intersection. To speed this
process, we may find which primitives may intersect a particular curve using
these functions, and iterate solely over the potentially intersecting
primitives. This significantly improves performance since primfind uses an
underlying tree structure to speed up search.
Examples
Remove primitives that may be intersecting the unit box centered at the origin:
int[] prims = primfind(geometry, {-0.5, -0.5, -0.5}, {0.5, 0.5, 0.5}); foreach ( int prim; prims ) { removeprim("primitives.bgeo", prim, 1); }
Alternatively, we can use a query bounding box from an auxiliary source:
vector min, max; getbbox("bbox.bgeo", min, max); int[] prims = primfind(geometry, min, max); foreach ( int prim; prims ) { removeprim("primitives.bgeo", prim, 1); }
To see the performance benefit of primfind, compare it to the following equivalent
implementation of the function above:
float tol = 1e-5; vector min, max; getbbox("bbox.bgeo",min,max); int n = nprimitives(0); for ( int prim = 0; prim < n; ++prim ) { int[] verts = primvertices("primitives.bgeo", prim); // compute primitive bounding box and store it in prim_min and prim_max vector vert_pos = point("primitives.bgeo", "P", vertexpoint("primitives.bgeo", verts[0])); vector prim_min = vert_pos, prim_max = vert_pos; for ( int v = 1; v < len(verts); ++v ) { vert_pos = point("primitives.bgeo", "P", vertexpoint("primitives.bgeo", verts[v])); prim_min = min(prim_min, vert_pos); prim_max = max(prim_max, vert_pos); } // bounding box intersection test if ( prim_max.x - min.x < -tol ) continue; if ( prim_max.y - min.y < -tol ) continue; if ( prim_max.z - min.z < -tol ) continue; if ( prim_min.x - max.x > tol ) continue; if ( prim_min.y - max.y > tol ) continue; if ( prim_min.z - max.z > tol ) continue; removeprim("primitives.bgeo", prim, 1); }
| See also | |
| intersect | |
| prim |
|
| search |