Handling Translucency with Real-Time Ray Tracing

Abstract

Translucency is a hard problem in real-time rendering. Despite the various techniques introduced to handle translucency in rasterization, the result is far from satisfactory, due to the limited geometry surface information outside of the screen space. For example, multi-layer alpha blending is nontrivial to implement and can still fail in many cases, not to mention rendering physically based translucency effects like refraction and absorption. This chapter provides an overview of translucent rendering effects with the aid of hardware-accelerated ray tracing. Ray tracing allows techniques to become possible that are not possible with rasterization, while also improving others. We are going to show how to implement transparency in ray tracing while also discussing trade-offs between correctness and accuracy. Instead of focusing on explaining different algorithms, the major focus of this chapter is implementation. This chapter will use the terminology of DirectX Raytracing (DXR) for simplicity, but the methods can also be applied for Vulkan.