610,611c610,613
<   // front should be greater than 0.0001
<   if (nearz < 0.0001)
---
>   // nearz should be greater than 0.0001 for perspective projections.
>   // For parallel projections, negative values of nearz are ok.
>   // Otherwize, the actors would get clipped by the near plane.
>   if (!this->ParallelProjection && nearz < 0.0001)