The Magic of Computer Graphics: Landmarks in Rendering
Noriko Kurachi, Michael Stark
Format: PDF / Kindle (mobi) / ePub
Author note: Edited by Michael Stark
Computer graphics is a vast field, and getting larger every day. It is impossible to cover every topic of interest, even within a specialization such as CG rendering. For many years, Noriko Kurachi has reported on the latest developments for Japanese readers in her monthly column for CG World. Being something of a pioneer herself, she selected topics that represented original and promising new directions for research, as opposed to the tried and true methods.
Many of these novel ideas paid off handsomely, and these are the topics covered in this book. Starting from the basic behavior of light, Ms. Kurachi introduces the most useful techniques for global and local illumination using geometric descriptions of an environment in the first section. She then goes on to describe image-based techniques that rely on captured data to do their magic in the second section. In the final section, she looks at the synthesis of these two complementary approaches and what they mean for the future of computer graphics.
"The book you hold today tells the story of this new era of computer graphics. Working closely with researchers who helped lead this revolution, Noriko Kurachi describes these key innovations and brings them together as a coherent body of knowledge. Please read this book, practice the techniques, and figure out if they will allow you to create the visions you have in your mind." -Paul Debevec, pioneer in HDR imaging and image-based modeling
importance function. The BRDF is largest where the reflection is most significant, so it is a natural choice for an importance function in GI integration. However, the BRDF says nothing about the directions of the strongest incoming light. Photon simulation can be used to precompute the dominant light directions. When this information is used in conjunction with the BRDF, better sampling can be achieved. Figure 2.8 illustrates such an approach. In the figure, the hemisphere is divided into
are stored in a frame taken as the input for the process that computes the next bounce. The photons in the subsequent bounce are stored into the next photon texture. The simulation can be viewed as it evolves by displaying the texture for each bounce. The second problem, that of photon lookup in the rendering phase, is handled by transferring the photon-map information into a framebuffer. Ideally there would be one photon per pixel, and each pixel would contain the index of the photon in the
visible glow in a phenomenon known as incandescence. The emission spectrum of an incandescent source is typically modeled as a black body, which is an object that absorbs all incident irradiance. The absorbed energy is re-emitted in a spectral distribution according to a Plank curve. The apparent color of a black body changes with temperature: as an object is heated it first appears a dull reddish orange, then shifts to a yellowish color and eventually to almost white (this is the origin of color
reproducing what an object or scene would look like if it were constructed and photographed, and this involves simulating how reflected and scattered light illuminate a real environment. The interaction of light and matter in nature is very complicated, and has been studied in the natural sciences for many years. By the mid-twentieth centuryit had become commonplace in manufacturing to represent objects using spatial coordinates and mathematical expressions. New approaches for representing curved
Here σt = σs + σa , σs = (1 − g)σs . The value σs is known as the reduced scattering coefficient; g is the “scattering anisotropy” from Equation (3.3.3). As g approaches 1 the scattering has a stronger forward bias, which has less influence on the net flux. Combining Equations (4.3) and (4.5) produces ∇2 φ (x) = 3σa σt φ (x) − 3σt Q0 (x) + ∇ · Q1(x), (4.6) which is one form of the diffusion equation. The diffusion equation given in Equation (4.6) describes how particles are diffused within a