Rendering Techniques for Transparent Objects

Three techniques are proposed for more realistic image synthesis of transparent objects. The techniques simulate important phenomena due to refraction and/or reflection, such as focuses and dispersion. For efficient simulation of focuses and caustics, a method called grid-pencil tracing is proposed, based on the ideas of pencil tracing and backward ray tracing. An anti-aliasing filter is designed for grid-pencil tracing in area-source illumination environments. The theory of pencil tracing is also applied to dispersion simulation. An extension of the theory provides a basis for dispersi ve pencil tracing, where both spatial coherency and 'wavelength coherency' is effectively used for fast image synthesis of dispersive objects. Furthermore, a linear filtering technique is applied to effectively express extremely bright spots such as sunshine reflection. The technique is based on an analysis of a special camera filter called a 'cross-screen filter,' which emphasizes bright spots by producing star-like lines around the spots on the image. With these techniques, the realism of transparent object images can be much enhanced in an inexpensive way.