Catálogo de publicaciones - libros

We present a novel and simple algorithm to automatically handle nested volumes and transitions between volumes, enabling push-button rendering functionality. The only requirements are the use of closed, watertight volumes (along with a ray tracing implementation such as NVIDIA RTX that guarantees watertight traversal and intersection) and that neighboring volumes are not intended to intersect each other, except for a small overlap that actually will model the boundary between the volumes.

We present a technique to hide the abrupt shadow terminator line when strong bump or normal maps are used to emulate micro-geometry. Our approach, based on microfacet shadowing functions, is simple and inexpensive. Instead of rendering detailed and expensive height-field shadows, we apply a statistical solution built on the assumption that normals follow a nearly normal random distribution. We also contribute a useful approximate variance measure for GGX, which is otherwise undefined analytically.

Efficient and accurate shadow computation is a long-standing problem in computer graphics. In real-time applications, shadows have traditionally been computed using the rasterization-based pipeline. With recent advances of graphics hardware, it is now possible to use ray tracing in real-time applications, making ray traced shadows a viable alternative to rasterization. While ray traced shadows avoid many problems inherent in rasterized shadows, tracing every shadow ray independently can become a bottleneck if the number of required rays rises, e.g., for high-resolution rendering, for scenes with multiple lights, or for area lights. Therefore, the computation should focus on image regions where shadows actually appear, in particular on the shadow boundaries.

We present a practical method for ray traced shadows in real-time applications. Our method uses the standard rasterization pipeline for resolving primary-ray visibility and ray tracing for resolving visibility of light sources. We propose an adaptive sampling algorithm for shadow rays combined with an adaptive shadowfiltering method. These two techniques allow computing high-quality shadows with a limited number of shadow rays per pixel. We evaluated our method using a recent real-time ray tracing API (DirectX Raytracing) and compare the results with shadow mapping using cascaded shadow maps.

This chapter presents a hybrid algorithm that uses ray tracing and rasterization to render surface and volumetric caustics in single scattering participating media. The algorithm makes use of ray tracing based on DirectX Raytracing (DXR) to generate data that drives hardware tessellation to adaptively refine triangular beam volumes that are rendered to slice volumetric caustics. Further on in the rendering pipeline, ray tracing is also used to generate secondary caustics maps that store the positions of ray/scene intersections for light rays that get reflected or refracted by a water surface.

With the recent arrival of ray tracing to the real-time graphics pipeline, developers are faced with a new challenge: figuring out how to make the most of the rays that they’re able to trace. One important question to decide is for which lighting effects to trace rays—choices include shadows, reflections, ambient occlusion, and full global illumination.

Another important question is how to choose which rays to trace for the chosen effect; an introduction to that question is the topic of this chapter. In the following, we will see how most lighting calculations in rendering can be interpreted as estimating the values of integrals and how tracing rays is a natural fit to an effective numerical integration technique: Monte Carlo. Given some background in Monte Carlo integration, we then see how well-chosen rays can dramatically improve the speed of convergence, which in turn can either improve overall system performance—by getting the same quality result for fewer rays—or improve image quality—by getting lower error from the same number of rays.

We present several formulas and methods for generating samples distributed according to a desired probability density function on a specific domain. Sampling is a fundamental operation in modern rendering, both at runtime and in preprocessing. It is becoming ever more prevalent with the introduction of ray tracing in standard APIs, as many ray tracing algorithms are based on sampling by nature. This chapter provides a concise list of some useful tricks and methods.

Ray tracing’s greatest strength—that it can simulate all types of light transport—can also be its greatest weakness: when there are a few paths that unexpectedly carry much more light than others, the produced images contain a smattering of pixels that have bright spiky noise. Not only can it require a prohibitive number of additional rays to average out those spikes, but those pixels present a challenge for denoising algorithms. This chapter presents two techniques to address this problem, preventing it from occurring in the first place.

The introduction of standardized APIs for ray tracing, together with hardware acceleration, opens up possibilities for physically based lighting in real-time rendering. Light importance sampling is one of the fundamental operations in light transport simulations, applicable to both direct and indirect illumination. This chapter describes a bounding volume hierarchy data structure and associated sampling methods to accelerate importance sampling of local light sources. The work is based on recently published methods for light sampling in production rendering, but it is evaluated in a real-time implementation using Microsoft DirectX Raytracing.

We present cinematic quality real-time rendering by integrating ray tracing in Unreal Engine 4. We improve the state-of-the-art performance in GPU ray tracing by an order of magnitude through a combination of engineering work, new ray tracing hardware, hybrid rendering techniques, and novel denoising algorithms.

Unlike rasterization, where one can rely on pixel quad partial derivatives, an alternative approach must be taken for filtered texturing during ray tracing. We describe two methods for computing texture level of detail for ray tracing. The first approach uses ray differentials, which is a general solution that gives high-quality results. It is rather expensive in terms of computations and ray storage, however. The second method builds on ray cone tracing and uses a single trilinear lookup, a small amount of ray storage, and fewer computations than ray differentials. We explain how ray differentials can be implemented within DirectX Raytracing (DXR) and how to combine them with a G-buffer pass for primary visibility. We present a new method to compute barycentric differentials. In addition, we give previously unpublished details about ray cones and provide a thorough comparison with bilinearly filtered mip level 0, which we consider as a base method.