# Physically Based Rendering: From Theory to Implementation

## Matt Pharr, Greg Humphreys

Language: English

Pages: 860

ISBN: B01M013UX1

Format: PDF / Kindle (mobi) / ePub

From movies to video games, computer-rendered images are pervasive today. **Physically Based Rendering** introduces the concepts and theory of photorealistic rendering hand in hand with the source code for a sophisticated renderer. By coupling the discussion of rendering algorithms with their implementations, Matt Pharr and Greg Humphreys are able to reveal many of the details and subtleties of these algorithms. But this book goes further; it also describes the design strategies involved with building real systems-there is much more to writing a good renderer than stringing together a set of fast algorithms. For example, techniques for high-quality antialiasing must be considered from the start, as they have implications throughout the system. The rendering system described in this book is itself highly readable, written in a style called *literate programming* that mixes text describing the system with the code that implements it. Literate programming gives a gentle introduction to working with programs of this size. This lucid pairing of text and code offers the most complete and in-depth book available for understanding, designing, and building physically realistic rendering systems.

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however. An example of such a shape is a triangle; see Figure 3.1. Shape Interface ✁✁ ✂ virtual BBox ObjectBound() const = 0; Shape Interface ✁✁ ✂ virtual BBox WorldBound() const { return ObjectToWorld(ObjectBound()); } 3.1.2 Refinement Not every shape needs to be capable of determining whether a ray intersects it. For example, a complex surface might first be tessellated into triangles, which can then be intersected directly. Another possibility is a shape that is a place-holder for a

Transform &obj2world, const DifferentialGeometry &dg, DifferentialGeometry *dgShading) const { *dgShading = dg; } 3.1.5 Surface Area In order to properly use Shapes as area lights, we need to be able to compute the surface area of a shape in object space. As with the intersection methods, this method will only be called for intersectable shapes. Shape Interface ✁✁ ✂ virtual Float Area() const { Severe("Unimplemented Shape::Area() method called"); return 0.; } 3.1.6 Sidedness Many rendering

vertices adjacent to each vertex (called the one-ring around it, reflecting the fact that it’s a ring of neighbors) and weight each of the neighbor vertices by a weight β (Figure 3.15.). The vertex we are updating, in the center, is weighted by 1 nβ, where n is the valence of the vertex. Thus, the new position v ☎ for a vertex v is: ✂ 1 nβ ✁ v ∑ βvi ☎ N v☎ i 1 This formulation ensures that the sum of weights is one, which guarantees the convex hull property we used above for

voxel grid ✁ } The first task is to determine where the ray enters the grid, which gives the starting point for traversal through the voxels. If the ray’s origin is inside the grid’s bounding box, then clearly it begins there. Otherwise the GridAccel::Intersect() method finds the intersection of the ray with the grid’s bounding box. If it hits, the first intersection along the ray is the starting point. If the ray misses the grid’s bounding box, there can be no intersection with any of the

in running time and memory use for a variety of scenes. 4.9 Investigate alternative cost functions for building kd-trees for the KdTreeAccel. How much can a poorly cost function hurt its performance? How much improvement can be had compared to the current one? 4.10 Geometry caching: hold limited amount in memory, discard as needed and call Primitive::Refine() later if geometry is needed again. LRU scheme... 4.11 The grid and kd-tree accelerators both take a 3D region of space, subdivite it into