griefith/test
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Fix #130969: OBJ import shading artifacts when file contains zero-area faces

Browse Source 
When OBJ file contains vertex normals, this can in some cases confuse
the custom loop normals code inside Blender. Since it does not simply
just use custom normals, but rather projects them into "lnor space".
But that "lnor space" calculation can go haywire sometimes, when
degenerate faces are present in the input.

Mark zero-area faces as "sharp" before doing custom normals. This will
make them not try to share the "smooth fan" lnor space with other faces,
and things will look correct.

Previously, OBJ importer was (wrongly) always setting all faces
as "sharp", which avoided this problem, but caused other issues.

Pull Request: https://projects.blender.org/blender/blender/pulls/131041
This commit is contained in:
Aras Pranckevicius
2024-11-27 22:03:15 +01:00
committed by Aras Pranckevicius
parent 1105f2573e
commit 3d7359a38f
1 changed files with 22 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
View File

@@ -205,18 +205,16 @@ void MeshFromGeometry::create_faces(Mesh *mesh, bool use_vertex_groups)
dverts = mesh->deform_verts_for_write();
}
Span<float3> positions = mesh->vert_positions();
MutableSpan<int> face_offsets = mesh->face_offsets_for_write();
MutableSpan<int> corner_verts = mesh->corner_verts_for_write();
bke::MutableAttributeAccessor attributes = mesh->attributes_for_write();
bke::SpanAttributeWriter<int> material_indices =
attributes.lookup_or_add_for_write_only_span<int>("material_index", bke::AttrDomain::Face);
const bool do_sharp = !has_normals();
bke::SpanAttributeWriter<bool> sharp_faces;
if (do_sharp) {
sharp_faces = attributes.lookup_or_add_for_write_span<bool>("sharp_face",
bke::AttrDomain::Face);
}
const bool set_face_sharpness = !has_normals();
bke::SpanAttributeWriter<bool> sharp_faces = attributes.lookup_or_add_for_write_span<bool>(
"sharp_face", bke::AttrDomain::Face);
int corner_index = 0;
@@ -229,9 +227,12 @@ void MeshFromGeometry::create_faces(Mesh *mesh, bool use_vertex_groups)
}
face_offsets[face_idx] = corner_index;
if (do_sharp) {
if (set_face_sharpness) {
/* If we have no vertex normals, set face sharpness flag based on
* whether smooth shading is off. */
sharp_faces.span[face_idx] = !curr_face.shaded_smooth;
}
material_indices.span[face_idx] = curr_face.material_index;
/* Importing obj files without any materials would result in negative indices, which is not
* supported. */
@@ -257,12 +258,23 @@ void MeshFromGeometry::create_faces(Mesh *mesh, bool use_vertex_groups)
corner_index++;
}
if (!set_face_sharpness) {
/* If we do have vertex normals, we do not want to set face sharpness.
* Exception is, if degenerate faces (zero area, with co-colocated
* vertices) are present in the input data; this confuses custom
* corner normals calculation in Blender. Set such faces as sharp,
* they will be not shared across smooth vertex face fans. */
const float area = bke::mesh::face_area_calc(
positions, corner_verts.slice(face_offsets[face_idx], curr_face.corner_count_));
if (area < 1.0e-12f) {
sharp_faces.span[face_idx] = true;
}
}
}
material_indices.finish();
if (do_sharp) {
sharp_faces.finish();
}
sharp_faces.finish();
}
void MeshFromGeometry::create_vertex_groups(Object *obj)