I have been trying to make a generic model class in c++ that can use any underlying data type, defined by it's BGFX layout. To do this I have been using assimp to import the model data. Unfortunately I have been finding that the indices and the vertices appear to be mismatched, and I've tracked the problem down to the function that processes the indices and vertices. This issue persists even when I am only importing the positions and there is no offset between them, and so I am unsure as to where I am going wrong when importing. The mesh class I am importing the data to copies data based on a void* pointer to the source, an offset in bytes to copy into within the mesh buffer, and the size of the data to copy in bytes.
The problematic function:
void ProcessVerticesAndIndices(const aiMesh* mesh, SGModel::Mesh& meshtmp)
{
using namespace bgfx;
using namespace SGModel;
//Preallocate memory
meshtmp.reserveVerticesData(mesh->mNumVertices * meshtmp.layout().getSize(1));
meshtmp.reserveIndicesData(mesh->mNumFaces * TRIANGULATED_VERTEX_COUNT * sizeof(Indice));
size_t vertex_size = meshtmp.layout().getSize(1);
for (size_t i = 0; i < mesh->mNumVertices; ++i)
{
//Process vertices
if (mesh->HasPositions())
{
//Type sizes are the size of the primitive type of the attribute (e.g. sizeof(float), sizeof(int32_t) etc)
uint8_t pos_type_size = GetBGFXAttributeTypeSize(GetBGFXAttributeType(Attrib::Position));
meshtmp.copyVertices(&mesh->mVertices[i].x, i * vertex_size, pos_type_size);
meshtmp.copyVertices(&mesh->mVertices[i].y, i * vertex_size + pos_type_size, pos_type_size);
meshtmp.copyVertices(&mesh->mVertices[i].z, i * vertex_size + 2 * pos_type_size, pos_type_size);
}
}
size_t indices_index = 0;
for(size_t i = 0; i < mesh->mNumFaces; ++i)
{
auto face = mesh->mFaces[i];
for (size_t j = 0; j < face.mNumIndices; ++j)
{
meshtmp.copyIndices(&face.mIndices[j], indices_index * sizeof(Indice), sizeof(Indice));
indices_index++;
}
}
}
The console print of the cube vertices, and indices:
VERTICES (in buffer order):
Index: 0
POS: 4 4 4
Index: 1
POS: -4 4 4
Index: 2
POS: -4 -4 4
Index: 3
POS: 4 -4 4
Index: 4
POS: 4 -4 -4
Index: 5
POS: 4 -4 4
Index: 6
POS: -4 -4 4
Index: 7
POS: -4 -4 -4
Index: 8
POS: -4 -4 -4
Index: 9
POS: -4 -4 4
Index: 10
POS: -4 4 4
Index: 11
POS: -4 4 -4
Index: 12
POS: -4 4 -4
Index: 13
POS: 4 4 -4
Index: 14
POS: 4 -4 -4
Index: 15
POS: -4 -4 -4
Index: 16
POS: 4 4 -4
Index: 17
POS: 4 4 4
Index: 18
POS: 4 -4 4
Index: 19
POS: 4 -4 -4
Index: 20
POS: -4 4 -4
Index: 21
POS: -4 4 4
Index: 22
POS: 4 4 4
Index: 23
POS: 4 4 -4
INDICES (in buffer order):
0
1
2
0
2
3
4
5
6
4
6
7
8
9
10
8
10
11
12
13
14
12
14
15
16
17
18
16
18
19
20
21
22
20
22
23
The render output (should be a black cube):
