Explnation about allocVBO function sop cpp node

Beginners
1

I`m going over the gpu direct option to implement in a plugin.
looking inside the the sop cpp example.

Can someone explain this lines of this code ?
the comments are bit confusing along side the variables names …
what the number 12 represent ?

int32_t numVertices = 12; int32_t numIndices = 12; output->allocVBO(numVertices, numIndices, VBOBufferMode::Static);

Even if i reduce the numIndices to 1 - it still works…
(seem like buffer update thing)

as far as i understand now:

the cube example it can be :

int32_t numVertices = 8; int32_t numIndices = 12; output->allocVBO(numVertices, numIndices, VBOBufferMode::Static);

numVertices means number of vertices.
numIndices means number of triangles .

in the commnet your description is :

thank you.
Barak

2

A primitive is made up of indices to select each vertex that makes it up. So for example a triangle requires 3 indices to be defined. You could have only 5 points, but 50 triangles made up of various combinations of those 5 points, requiring 150 indices.

3

Thanks for the explanation,
maybe this one could be written differently…

// 'numVertices' is how much memory to allocate for positions/normals etc.
4

Yep for sure, we’ll reword that. Thanks!