int osd_lookupface(<geometry>geometry, int patch_id, float patch_u, float patch_v, int &face_id, float &face_u, float &face_v)
If you don’t specify a texture attribute, the function uses intrinsic polygon interpolants.
int osd_lookupface(<geometry>geometry, int patch_id, float patch_u, float patch_v, int &face_id, float &face_u, float &face_v, string attribute)
If you specify a texture attribute, the function uses the UVs in that attribute to translate the patch coordinates onto the Houdini geometry.
Each polygon in a piece of geometry will generate one or more Catmull-Clark subdivision patches. A quadrilateral will generate a single patch, while a pentagon will generate five patches. This function helps map between the subdivision patch id and the Houdini polygon (face). The reverse function to map from face to patch is osd_lookuppatch.
<geometry>
When running in the context of a node (such as a wrangle SOP), this argument can be an integer representing the input number (starting at 0) to read the geometry from.
Alternatively, the argument can be a string specifying a geometry file (for example, a .bgeo) to read from. When running inside Houdini, this can be an op:/path/to/sop reference.
patch_id
The ID number of the OSD patch.
patch_u, patch_v
The coordinates in the subdivision patch to map onto a Houdini primitive. These values should be in the range 0 to 1.
&face_id
The function overwrites this variable with the Houdini primitive number of the corresponding face.
&face_u, &face_v
The function overwrites these variables with the corresponding U/V coordinates on the Houdini face. The output coordinates will have values in the range 0 to 1.
Returns
1 on success or 0 on an error.
Examples ¶
void scatterOnLimitSurface(string file, texmap; int geo_handle; int npts) { int npatches = osd_patchcount(file); for (int i = 0; i < npts; ++i) { int patch_id = nrandom() * npatches; float patch_s = nrandom(); float patch_t = nrandom(); int face_id; float face_u, face_v; if (osd_lookupface(file, patch_id, patch_s, patch_t, face_id, face_u, face_v, "uv")) { vector clr = texture(texmap, face_u, face_v); vector P; osd_limitsurface(file, "P", patch_id, patch_s, patch_t, P); int ptnum = addpoint(geo_handle, P); // add a scattered point. if (ptnum >= 0) { addpointattrib(geo_handle, "Cd", clr); addpointattrib(geo_handle, "face_id", face_id); } } } }
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