[Plib-devel] Automatic normals in the OBJ loader.

[<jeb...@fr...>]

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	Hi,

	I need to write an application that will load objects from .obj
files with no normal information included in the file. It would be
nice if PLIB could test for this case and generate some reasonable
normals automatically.

	I have implemented this function and it works on the files I have
tested (without breaking those files that *include* normal
information of course). In the function add_mesh (ssgLoadOBJ.cxx,
line 310 for version 1.8.4), I added the following code:

// Create the normals
if (num_vert_normal == 0) {
  memset (vert_normal, 0, sizeof (vert_normal));
  for (i = 0; i < num_face; ++i) {
    sgVec3 v1, v2, faceNormal;
    sgSubVec3 (v1, vert[face[i].vlist[1]], vert[face[i].vlist[0]]);
    sgSubVec3 (v2, vert[face[i].vlist[2]], vert[face[i].vlist[0]]);
    sgVectorProductVec3 (faceNormal, v1, v2);
    sgAddVec3 (vert_normal[face[i].vlist[0]], faceNormal);
    sgAddVec3 (vert_normal[face[i].vlist[1]], faceNormal);
    sgAddVec3 (vert_normal[face[i].vlist[2]], faceNormal);
    face[i].nlist[0] = face[i].vlist[0];
    face[i].nlist[1] = face[i].vlist[1];
    face[i].nlist[2] = face[i].vlist[2];
  }
  num_vert_normal = num_vert;
  for (i = 0; i < num_vert_normal; ++i)
    sgNormalizeVec3 (vert_normal[i]);
}

	Of course, the resulting normals aren't perfect, but they're still
a lot better than what happens when there is no normal information
at all.

		Jerome
- --
+------------------------- Jerome M. BERGER ---------------------+
|    mailto:jeb...@fr...      | ICQ:    238062172            |
|    http://jeberger.free.fr/     | Jabber: jeb...@ja...   |
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