gistfile1.cpp

    void Terrain::generateIndices() {
        // we calculate the amount of levels and make the index buffers
        int level_max = log2(patch_size - 1);
        
        indexCount = new GLuint[level_max + 1];
        indexBuffer = new GLuint[level_max + 1];
        

        for(int l = 0; l < level_max; ++l)
        {
            // make a container for the indices, calculate the
            // patch size for this level, and init the index counter
            int patch_size_level = pow(2,level_max - l) + 1;
            int current_index = 0;
            indexCount[l] = (2*patch_size_level+1) * (patch_size_level - 1);            
            GLuint* indices = new GLuint[indexCount[l]];            
            
            for(int i = 0; i < patch_size - 1; i += pow(2,l)){
                if((int)(i/pow(2,l)) % 2 == 0) {
                    // dir ---->
                    for(int j = 0; j < patch_size; j += pow(2,l)) {
                        indices[current_index] = (i * patch_size) + j;
                        ++current_index;
                        indices[current_index] = ((i + pow(2,l)) * patch_size) + j;
                        ++current_index;
                    }
                    indices[current_index] = (i + pow(2,l) + 1) * patch_size - 1; //make degenerate triangle
                    ++current_index;
                }
                else {
                    // dir <----
                    for(int j = 0; j < patch_size; j += pow(2,l)) {
                        indices[current_index] = (i + 1) * patch_size - 1 - j;
                        ++current_index;
                        indices[current_index] = (i + 1 + pow(2, l)) * patch_size - 1 - j;
                        ++current_index;
                    }
                    indices[current_index] = (i + pow(2,l)) * patch_size; //make degenerate triangle
                    ++current_index;
                }
            }
                        
            // save the indexbuffer
            glGenBuffers(1, &indexBuffer[l]);
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer[l]);
            glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GL_UNSIGNED_INT) * indexCount[l], indices, GL_STATIC_DRAW);
          
            delete[] indices;
        }
        
    }