hello guys .
i am working on an endless runner project , and in my project i am using object pooling , in a way that most of my environment is pooled and spawned together. so i have recently decided to reduce my draw calls (Set pass calls ). at first i had multiple fbx files , so i decided to move all my files to just one fbx .
i am using houdini as modeling software , and in houdini 
i 've added each of my geometries as a file node in houdini then i exported the resulting geometry as an output FBX.
and houdini turns this for me to only ONE geometry.
when i export this geometry and bring it to unity , and i should mention , i am just using the unity default material , and no textures . when i hit play there is 5 draw calls .
i know why there are 5 draw calls , because i have 5 geometries combined into one single geometry, but isn’t unity suppose to use only one draw call per mesh ?
here is my question , why there is 5 draw calls for only one mesh ? and i 've read one answer that in forward rendering there is one draw call for each gameobject , and my camera’s rendering is forward .
and if problem is in houdini side , i would appreciate if you tell me how to fix it .
thanks a lot.