Thread: void pointer and dynamic memory help

hi im using VC++.net and writing a 3d game engine with directx 8.1, however i have run into a problem which i cant find a solution to. (this is a simple problem and has nothing to do with directx or 3d graphics theory)

this is my problem, i have a void pointer which is initalized to be an array of 4 structs, however depending on the flow of the program it is not always intialized into the same type.

this is an example:

//the vertex pointer whos type is set by eather having lighting or not
void * vertices;


//if there is lighting
//define vertex type for light
reinterpret_cast <VertexLitTex *> ( vertices) = new VertexLitTex[ 4 ];


//if there is no lighting
//no normals are needed
reinterpret_cast <VertexTex *> ( vertices ) = new VertexTex[ 4 ];

then later on in the constructor i go on to set the values of the structs, it must be done this way. this is where i get the problem
the error is: "error C2106: '=' : left operand must be l-value".
i know what the problem is and what is wrong, i just dont know the solution.

what i want to say is basicly this:
...
vertices[ 0 ].x = -half_height;
vertices[ 0 ].y = half_height;
...
i have tried this and other varients but they all yield the same error:

reinterpret_cast <VertexLitTex *> ( vertices[ 0 ].x &nbsp = half_height;

thank you for your time,
your help is greatly appreciated!

I can think of one way to solve the problem...

Create a base class Vertex, and derive VertexTex and VertexLitTex from it... then instead of using a void * you can use a Vertex *. The use a dynamic_cast<> one you determine which class you'll need to use.

thank you man,
i never thought about that,
i will try it.

i have thought about that, and i dont belive it will work. because it "downcasts" a Vertex class to a VertexLitTex class, because VertexLitTex is the derived class from Vertex:

Code:

class Vertex
{
public:
     float x, y, z;
     DWORD color;
};

class VertexLitTex : public Vertex
{
public:
     float nx, ny, nz;  //vertex normals
     float u, v;           //texture coords
};

well time is my enemy here, this projects deadline is fastly approching, so i belive i will just make two arrays and use wichever. -its dirty but it will do the job

thanks again man