3D graphics eBook - Course Materials Repository

More documents

Recommendations

Info

Path tracing 99 } Color reflected = TracePath(newRay,depth+1); return emittance + ( BDRF * cos_omega * reflected ); In the above example if every surface of a closed space emitted and reflected (0.5,0.5,0.5) then every pixel in the image would be white. Bidirectional path tracing In order to accelerate the convergence of images, bidirectional algorithms trace paths in both directions. In the forward direction, rays are traced from light sources until they are too faint to be seen or strike the camera. In the reverse direction (the usual one), rays are traced from the camera until they strike a light or too many bounces ("depth") have occurred. This approach normally results in an image that converges much more quickly than using only one direction. Veach and Guibas give a more accurate description veach1997metropolis : These methods generate one subpath starting at a light source and another starting at the lens, then they consider all the paths obtained by joining every prefix of one subpath to every suffix of the other. This leads to a family of different importance sampling techniques for paths, which are then combined to minimize variance. Performance A path tracer continuously samples pixels of an image. The image starts to become recognisable after only a few samples per pixel, perhaps 100. However, for the image to "converge" and reduce noise to acceptable levels usually takes around 5000 samples for most images, and many more for pathological cases. This can take hours or days depending on scene complexity and hardware and software performance. Newer GPU implementations are promising from 1-10 million samples per second on modern hardware, producing acceptably noise-free images in seconds or minutes. Noise is particularly a problem for animations, giving them a normally-unwanted "film-grain" quality of random speckling. Metropolis light transport obtains more important samples first, by slightly modifying previously-traced successful paths. This can result in a lower-noise image with fewer samples. Renderer performance is quite difficult to measure fairly. One approach is to measure "Samples per second", or the number of paths that can be traced and added to the image each second. This varies considerably between scenes and also depends on the "path depth", or how many times a ray is allowed to bounce before it is abandoned. It also depends heavily on the hardware used. Finally, one renderer may generate many low quality samples, while another may converge faster using fewer high-quality samples.
Path tracing 100 Scattering distribution functions The reflective properties (amount, direction and colour) of surfaces are modelled using BRDFs. The equivalent for transmitted light (light that goes through the object) are BTDFs. A path tracer can take full advantage of complex, carefully modelled or measured distribution functions, which controls the appearance ("material", "texture" or "shading" in computer graphics terms) of an object. Notes 1. Kajiya, J T, The rendering equation (http:/ / citeseerx. ist. psu. edu/ viewdoc/ download?doi=10. 1. 1. 63. 1402& rep=rep1& type=pdf), Proceedings of the 13th annual conference on Computer graphics and interactive techniques, ACM, 1986. 2. Lafortune, E, Mathematical Models and Monte Carlo Algorithms for Physically Based Rendering (http:/ / www. graphics. cornell. edu/ ~eric/ thesis/ index. html), (PhD thesis), 1996. Scattering distribution functions 3. Purcell, T J; Buck, I; Mark, W; and Hanrahan, P, "Ray Tracing on Programmable Graphics Hardware", Proc. SIGGRAPH 2002, 703 - 712. See also Purcell, T, Ray tracing on a stream processor (http:/ / graphics. stanford. edu/ papers/ tpurcell_thesis/ ) (PhD thesis), 2004. 4. Robison, Austin, "Interactive Ray Tracing on the GPU and NVIRT Overview" (http:/ / realtimerendering. com/ downloads/ NVIRT-Overview. pdf), slide 37, I3D 2009. 5. Vray demo (http:/ / www. youtube. com/ watch?v=eRoSFNRQETg); Other examples include Octane Render, Arion, and Luxrender. 6. Veach, E., and Guibas, L. J. Metropolis light transport (http:/ / graphics. stanford. edu/ papers/ metro/ metro. pdf). In SIGGRAPH’97 (August 1997), pp. 65–76. 7. This "Introduction to Global Illumination" (http:/ / www. thepolygoners. com/ tutorials/ GIIntro/ GIIntro. htm) has some good example images, demonstrating the image noise, caustics and indirect lighting properties of images rendered with path tracing methods. It also discusses possible performance improvements in some detail. 8. SmallPt (http:/ / www. kevinbeason. com/ smallpt/ ) is an educational path tracer by Kevin Beason. It uses 99 lines of C++ (including scene description). This page has a good set of examples of noise resulting from this technique.
Page 1 and 2:
3D Rendering PDF generated using th
Page 3 and 4:
Image-based lighting 64 Image plane
Page 5 and 6:
References Article Sources and Cont
Page 7 and 8:
3D rendering 2 Non real-time Animat
Page 9 and 10:
3D rendering 4 The shaded three-dim
Page 11 and 12:
Ambient occlusion 6 ambient occlusi
Page 13 and 14:
Ambient occlusion 8 • ShadeVis (h
Page 15 and 16:
Anisotropic filtering 10 will only
Page 17 and 18:
Beam tracing 12 Beam tracing Beam t
Page 19 and 20:
Bilinear filtering 14 Are all true.
Page 21 and 22:
Binary space partitioning 16 togeth
Page 23 and 24:
Binary space partitioning 18 Other
Page 25 and 26:
Binary space partitioning 20 [1] Bi
Page 27 and 28:
Bounding interval hierarchy 22 Prop
Page 29 and 30:
Bounding volume 24 bounding boxes b
Page 31 and 32:
Bump mapping 26 Bump mapping Bump m
Page 33 and 34:
CatmullClark subdivision surface 28
Page 35 and 36:
CatmullClark subdivision surface 30
Page 37 and 38:
Conversion between quaternions and
Page 39 and 40:
Cube mapping 34 Advantages Cube map
Page 41 and 42:
Cube mapping 36 Related A large set
Page 43 and 44:
Diffuse reflection 38 2), or, of co
Page 45 and 46:
Displacement mapping 40 Meaning of
Page 47 and 48:
DooSabin subdivision surface 42 Ext
Page 49 and 50:
False radiosity 44 False radiosity
Page 51 and 52:
Geometry pipelines 46 Geometry pipe
Page 53 and 54: Global illumination 48 Rendering wi
Page 55 and 56: Gouraud shading 50 Gouraud shading
Page 57 and 58: Graphics pipeline 52 Graphics pipel
Page 59 and 60: Graphics pipeline 54 References 1.
Page 61 and 62: Hidden surface determination 56 imp
Page 63 and 64: High dynamic range rendering 58 Hig
Page 65 and 66: High dynamic range rendering 60 Ton
Page 67 and 68: High dynamic range rendering 62 Fro
Page 69 and 70: High dynamic range rendering 64 •
Page 71 and 72: Irregular Z-buffer 66 Applications
Page 73 and 74: Lambert's cosine law 68 than would
Page 75 and 76: Lambertian reflectance 70 Lambertia
Page 77 and 78: Level of detail 72 Well known appro
Page 79 and 80: Level of detail 74 Hierarchical LOD
Page 81 and 82: Newell's algorithm 76 Newell's algo
Page 83 and 84: Non-uniform rational B-spline 78 Us
Page 85 and 86: Non-uniform rational B-spline 80 of
Page 87 and 88: Non-uniform rational B-spline 82 ar
Page 89 and 90: Non-uniform rational B-spline 84 Ex
Page 91 and 92: Normal mapping 86 How it works To c
Page 93 and 94: OrenNayar reflectance model 88 Oren
Page 95 and 96: OrenNayar reflectance model 90 , ,
Page 97 and 98: Painter's algorithm 92 The algorith
Page 99 and 100: Parallax mapping 94 • Parallax Ma
Page 101 and 102: Particle system 96 A cube emitting
Page 103: Path tracing 98 History Further inf
Page 107 and 108: Phong reflection model 102 Visual i
Page 109 and 110: Phong reflection model 104 Because
Page 111 and 112: Phong shading 106 Visual illustrati
Page 113 and 114: Photon mapping 108 Rendering (2nd p
Page 115 and 116: Photon tracing 110 Advantages and d
Page 117 and 118: Potentially visible set 112 • Can
Page 119 and 120: Potentially visible set 114 Externa
Page 121 and 122: Procedural generation 116 increases
Page 123 and 124: Procedural generation 118 • Softi
Page 125 and 126: Procedural generation 120 Reference
Page 127 and 128: Procedural texture 122 Self-organiz
Page 129 and 130: Procedural texture 124 References [
Page 131 and 132: 3D projection 126 The distance of t
Page 133 and 134: Quaternions and spatial rotation 12
Page 145 and 146: Radiosity 140 Overview of the radio
Page 147 and 148: Radiosity 142 This is sometimes kno
Page 149 and 150: Radiosity 144 References [1] " Mode
Page 151 and 152: Ray casting 146 the light will reac
Page 153 and 154: Ray tracing 148 Typically, each ray
Page 155 and 156:
Ray tracing 150 independence of eac
Page 157 and 158:
Ray tracing 152 On June 12, 2008 In
Page 159 and 160:
Reflection 154 Reflection Reflectio
Page 161 and 162:
Reflection 156 Glossy Reflection Fu
Page 163 and 164:
Reflection mapping 158 Cube mapping
Page 165 and 166:
Render Output unit 160 Render Outpu
Page 167 and 168:
Rendering 162 • indirect illumina
Page 169 and 170:
Rendering 164 Ray tracing Ray traci
Page 171 and 172:
Rendering 166 Academic core The imp
Page 173 and 174:
Rendering 168 • 1984 Distributed
Page 175 and 176:
Retained mode 170 Retained mode In
Page 177 and 178:
Scanline rendering 172 Comparison w
Page 179 and 180:
Screen Space Ambient Occlusion 174
Page 181 and 182:
Screen Space Ambient Occlusion 176
Page 183 and 184:
Shadow mapping 178 Algorithm overvi
Page 185 and 186:
Shadow mapping 180 Drawing the scen
Page 187 and 188:
Shadow mapping 182 Further reading
Page 189 and 190:
Shadow volume 184 There is also a p
Page 191 and 192:
Shadow volume 186 The depth fail me
Page 193 and 194:
Silhouette edge 188 Silhouette edge
Page 195 and 196:
Specular highlight 190 Specular hig
Page 197 and 198:
Specular highlight 192 normalized o
Page 199 and 200:
Sphere mapping 194 Sphere mapping I
Page 201 and 202:
Stencil codes 196 Stencil codes Ste
Page 203 and 204:
Stencil codes 198 Stencils The shap
Page 205 and 206:
Stencil codes 200 [7] Wellein, G et
Page 207 and 208:
Subdivision surface 202 used a four
Page 209 and 210:
Subsurface scattering 204 Subsurfac
Page 211 and 212:
Subsurface scattering 206 External
Page 213 and 214:
Surface normal 208 If a (possibly n
Page 215 and 216:
Surface normal 210 Normal in geomet
Page 217 and 218:
Texture filtering 212 Texture filte
Page 219 and 220:
Texture mapping 214 Texture mapping
Page 221 and 222:
Texture mapping 216 constant distan
Page 223 and 224:
Texture synthesis 218 • Structure
Page 225 and 226:
Texture synthesis 220 Pattern-based
Page 227 and 228:
Texture synthesis 222 • Micro-tex
Page 229 and 230:
UV mapping 224 A UV map can either
Page 231 and 232:
Vertex 226 Polytope vertices are re
Page 233 and 234:
Vertex Buffer Object 228 //Make the
Page 235 and 236:
Vertex Buffer Object 230 GLuint sha
Page 237 and 238:
Vertex Buffer Object 232 vertexes *
Page 239 and 240:
Virtual actor 234 Virtual actor A v
Page 241 and 242:
Virtual actor 236 exercises, and ev
Page 243 and 244:
Volume rendering 238 Volume ray cas
Page 245 and 246:
Volume rendering 240 Maximum intens
Page 247 and 248:
Volume rendering 242 Image-based me
Page 249 and 250:
Volumetric lighting 244 References
Page 251 and 252:
Voxel 246 • Outcast, a game made
Page 253 and 254:
Z-buffering 248 Z-buffering In comp
Page 255 and 256:
Z-buffering 250 } } display COLOR a
Page 257 and 258:
Z-fighting 252 Z-fighting Z-fightin
Page 259 and 260:
Appendix 3D computer graphics softw
Page 261 and 262:
3D computer graphics software 256
Page 263 and 264:
3D computer graphics software 258
Page 265 and 266:
3D computer graphics software 260 2
Page 267 and 268:
Article Sources and Contributors 26
Page 269 and 270:
Article Sources and Contributors 26
Page 271 and 272:
Image Sources, Licenses and Contrib
Page 273 and 274:
Image Sources, Licenses and Contrib
show all

3D graphics eBook - Course Materials Repository

Create successful ePaper yourself

Delete template?

Save as template?