How to start a static analysis with element density data?

Hello,

I am working on density-based method topology optimization. The compliance optimization is defined as:

• find X = [x_1, x_2, ... ]^T
• min u^T * K(X) * u
• such that K(X)*u = F and sum of all x_j * dV - V <=0
• (X: element density, u: displacement vector, K: global stiffness matrix, F: external force vector, V: constraint volume)

I want to start a linear static analysis with X = [x_1, x_2, ... ]^T initial element density as an input. Optistruct can optimize this process itself but I want to try novel filters, penalty algorithms, other optimization algorithms etc. without using optistruct topology optimization. 

To try this, I can modify the optistruct FEM file, for example defining different material and property for every mesh element. But this method takes a long time.

Optistruct has already suitable to optimize like that. How I can do easily what I explained?

Thanks.