How to Handle Separate Vertex and Normal Indices in OpenGL Using an Index Buffer?

OpenGL Index Buffer Challenges

In this scenario, the provided custom file format contains separate indices for vertices and normals, which poses a challenge when using OpenGL, as it expects a single set of indices. To resolve this issue, it is necessary to create an OpenGL vertex for each unique pairing of vertex index and normal index.

Solution Using Data Structures

Consider the following approach:

1. Create a map to store the (vertex index, normal index) pairs as keys, and unique combined indices as values.
2. Initialize a combined vertices array and an index list.
3. Iterate over each triangle in the input file.
4. For each corner of the triangle, read the vertex index and normal index.
5. Check if the (vertex index, normal index) pair exists in the map.
6. If it does, retrieve the combined index from the map.
7. If it doesn't, assign a new combined index, add the pair to the map, and add the combined vertex (comprising both vertex and normal coordinates) to the combined vertices array.
8. Add the combined index to the combined index list.

Vertex Duplication Handling

As mentioned in the problem, there may be duplicate vertices. To handle this, you can use a set or a hash table to store unique vertices. When you encounter a new vertex that is not in the set, add it to the set and the combined vertices array.

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