float friction_coeff = 0.1f;
float inv_mass_sum = entity1.inverse_mass+entity2.inverse_mass;
float reaction = (1+restitution)*inner_product(v_rel, c.normal)/inv_mass_sum;
float friction_coeff = 0.1f;
float inv_mass_sum = entity1.inverse_mass+entity2.inverse_mass;
float reaction = (1+restitution)*inner_product(v_rel, c.normal)/inv_mass_sum;