Order Independent Transparency with Per-Pixel Linked Lists

This paper proposes a method for rendering scenes of both opaque and transparent objects. Transparency depends on the attenuation coefficient and the thickness of the transparent object we wish to render. To get the visible radiance, the volume rendering equation should be solved. Instead of marching a ray, we build a list that contains the intersection points of the ray and object surfaces. In the second phase of rendering, the GPU sorts and processes the lists and evaluates the attenuation integrals analytically, considering also the order of the segments. This solution is mathematically correct even if objects intersect, i.e. it does not involve drastic simplifications, and provides high framerates even on moderately complex scenes, outperforming previous methods. In addition to transparent objects, the technique is also appropriate to visualize natural phenomena represented by particle systems.