float trafo(float n, float x)
{
    return -log(-n*(1-exp(-x))+1);
}

void SmokeRenderer::massCorrection( cell_list * cell_list, density_pic * density_pic )
{
    cudaMemcpy(alpha,&g_particleEngine->data().alpha->at(0),sizeof(float)*mNumParticles,cudaMemcpyDeviceToHost);
    cudaMemcpy(radius,&g_particleEngine->data().radius->at(0),sizeof(float)*mNumParticles,cudaMemcpyDeviceToHost);

    //exp transform based on direct vol rendering eqtn
    for (int i = 0; i < mNumParticles; i++)
    {
        float n = alpha[i]/0.1;
        alpha[i] = trafo(n,alpha[i]);
    }