Black triangles

when i create a mesh normaly useing createmesh, addtrinagle,ect the mesh is normaly a grey color untill a texture or brush is used, but sometimes it apears as black and when i add a texture, brush or any other efect it stays black, does anyone know why this is

ambient color 0,0,0 or something similar. (like forgot updatenormals after creation of the triangle data which is needed for light reaction)

ambient color only controls the world lighting though doesent it and in due course would alter the color of all meshes but my problem efects only the one mesh,
i have a tree trunk (that i made in blitz)
and a leaf chunk(also made in blitz) but the trunk takes texturing propely and the chunk doesent if i add an alpha to the leaf texture it stays black but in the perfect shape of the leaf texture???, i also have this problem when i run the example from addtriangle i have to change the cameraclscolor in order to see the ramp. i thought maybe it was my laptop but i get the same problem with my main computer.

Maybe it is lacking normals ? Try UpdateNormals() or else maybe EntityFX mesh, 1

Or lack of UVs. What Laptop/ main computer/ GFX card do you have?