Hi, I´d like to ask if anybody knows how can I invert the normals of the triangles of a mesh, and how to combine two or more entities into just one?

look at ent_buffers and D3DVERTEX
with those you can easily invert the normals of the model

i cant remember how i use to do
this on other graphic engines
i think i flipped triangle direction through
vertices indices 123 to 321 and recslculate
normals .dont realy on my word
i have not done in gamestudio
yet .there was also something about
backface culling direction cloclwise
or counter clockwise

I knew that if I recalculate the indices, the normal changes, but I need simpler method.

can you explain to me how do I use this function?ent_buffers.

Why would you need to do such thing, what are you trying to accomplish? You can easily change the cullmode in a shader so that you can f.i. show the backfaces of a model (or deactivate face culling completely) or even render the model multiple times with different cullmodes (for example for a cartoon outline shader).