Is there a way to quickly estimate how much geometry the marching cubes algorithm will produce? As in a ballpark estimate of num verts + num faces or STL file sizes?
I'm trying to implement a pre-triangulation check that tells the user to lower the resolution (i.e. use lower number of samples, spanning larger regions of space), or reduce the domain size before inadvertently trying to generate a multi-GB-large STL-file mesh of an implicit surface that no slicing software could cope with anyway.
In the worst case, I could probably just generate a whole bunch of STL's with different settings to find out these values.
It is not difficult to modify a Marching Cubes code so that it only counts the number of vertices and the number of triangles. I think that option that you propose can be useful. You only have to identify in which part of the code the vertices (and normals and colors) and the indices of the triangles are stored. In the case of the Marching Cubes 33 code for the C language that we programmed (marching_cubes_33_c_library_v4, MC33_libraries), the vertices are stored in the MC33_storePointNormal function. Instead of calling MC33_storePointNormal, the vertex counter is simply increased by 1. And in this specific case, the code that stores the indices of the triangles is eliminated, only the counter increment of the number of triangles is left.
I made a function that counts the number of vertices and triangles and calculates the amount of memory occupied by the surface:
This function calls the MC33_findCase_count function instead of calling the MC33_findCase function. You just need to copy the code for both functions at the end of the source/marching_cubes_33.c file and place the declaration of the memory_of_isosurface function in the include/marching_cubes_33.h file.
I benchmarked the function that only counts, and the execution time decrease is between 12 and 32%.
Important note: for reasons of size of the post, I removed a part of the code, switch (c>>8). This part of the code must be copied from the MC33_findCase function.