How Can I Overcome OpenGL\'s Single Index Buffer Limitation When Using Separate Vertex and Normal Indices?

Overcoming Index Buffer Limitations for OpenGL Meshes

In your scenario, where you have a custom file format with vertices, vertex indices, and normals with separate indices, you encounter a challenge that does not align with OpenGL's vertex model, which utilizes a single index buffer.

The solution lies in creating an OpenGL vertex for each unique combination of vertex index and normal index. Utilizing data structures like a STL map can simplify this process.

Considering your arrays inVertices and inNormals, where vertices are stored in inVertices[vertexIdx] and normals in inNormals[normalIdx], the following pseudo code outlines the approach:

nextCombinedIdx = 0
indexMap = empty
foreach triangle in input file:
   foreach corner of triangle:
      read vertexIdx and normalIdx
      if indexMap.contains((vertexIdx, normalIdx)):
         combinedIdx = indexMap.get((vertexIdx, normalIdx))
      else:
         combinedIdx = nextCombinedIdx
         indexMap.add((vertexIdx, normalIdx), combinedIdx)
         nextCombinedIdx = nextCombinedIdx + 1
         combinedVertices.add(inVertices[vertexIdx], inNormals[normalIdx])
      combinedIndices.add(combinedIdx)

This process ensures that each triangle corner is represented by a unique OpenGL vertex, combining both vertex and normal information. By employing a data structure like a map, you can efficiently map vertex-normal pairs to their corresponding OpenGL indices.

The above is the detailed content of How Can I Overcome OpenGL\'s Single Index Buffer Limitation When Using Separate Vertex and Normal Indices?. For more information, please follow other related articles on the PHP Chinese website!