Voxel-Based Global-Illumination

Transcription

1 Voxel-Based Global-Illumination By Thiedemann, Henrich, Grosch, and Müller Real-Time Near-Field Global Illumination on a Voxel Model (Morteza), M.Sc. Marc Treib

2 Overview Illumination What is voxelization? Paper s Voxelization Method Paper s Voxel/Ray Intersection Method Near Global-Illumination Based on Voxel-Model Results

3 Illumination Direct Illumination Indirect Illumination

4 Types of Illumination Direct Illumination Reflection can be computed locally (using Normal and Material Specification) Local Illumination

5 Types of Illumination Indirect Illumination The reflected light cannot be computed locally Global Illumination

6 Ray Tracing

7 Ray Tracing Algorithm Image Raytrace (Camera cam, Scene scene, int width, int height) { Image image = new Image (width, height) ; for (int i = 0 ; i < height ; i++) for (int j = 0 ; j < width ; j++) { Ray ray = RayThruPixel (cam, i, j) ; Intersection hit = Intersect (ray, scene) ; image[i][j] = FindColor (hit) ; } return image ; }

8 Ray Tracing Algorithm Image Raytrace (Camera cam, Scene scene, int width, int height) { Image image = new Image (width, height) ; for (int i = 0 ; i < height ; i++) for (int j = 0 ; j < width ; j++) { Ray ray = RayThruPixel (cam, i, j) ; Intersection hit = Intersect (ray, scene) ; image[i][j] = FindColor (hit) ; } return image ; }

9 Ray Tracing Accelaration Classification of Accelaration Techniques for ray tracing Faster ray-object intersections Fewer Ray-Object Intersections Fewer Rays

10 What is voxelization?

11 Types of Voxelization Binary Voxelization A cell stores whether geometry is present in this cell or not Multi-Valued Voxelization A cell can also stores arbitrary other data like BRDF, normal or Radiance Boundary Voxelization Encodes the object surfaces only Solid Voxelization Captures the interior of a model

12 Contributions A new atlas-based voxelization method An improved ray/voxel intersection test Real-time near-field illumination with voxel visibility

13 Goal Computing global illumination in real time, given a large and dynamic scene.

14 Atlas-Based Voxelization (1/5)

15 Atlas-Based Voxelization (2/5)

16 Atlas-Based Voxelization (3/5) Performance is directly related to the number of rendered vertices Sufficient atlas-texture resolution

17 Atlas-Based Voxelization (4/5) Environment Geforce GTX 295, Intel Core 2 Duo 3.16 Ghz, 4 GB RAM Performance

18 Atlas-Based Voxelization (5/5) Pros No restrictions to the objects Applicable for dynamics rigid bodies and moderately deforming models Cons Each object has to have a texture atlas Low atlas texture resolution causes holes in voxelization Not allow strong deformation of the objects

19 Ray Tracing Accelaration Classification of Accelaration Techniques for ray tracing Faster ray-object intersections Efficient intersectors Fewer Ray-Object Intersections Bounding Volumes (Boxes, Spheres) Space Subdivision Fewer Rays Adaptive Tree-Depth Control Stochastic Sampling

20 Hierarchical Ray-Voxel Intersection Test (1/3) Use a binary voxelized scene representation(why only in 2-dimensions) Build a Maximum mip-map hierarchy

21 Hierarchical Ray-Voxel Intersection Test (2/3)

22 Hierarchical Ray-Voxel Intersection Test (2/3)

23 Hierarchical Ray-Voxel Intersection Test (2/3)

24 Hierarchical Ray-Voxel Intersection Test (2/3)

25 Hierarchical Ray-Voxel Intersection Test (2/3)

26 Hierarchical Ray-Voxel Intersection Test (2/3)

27 Hierarchical Ray-Voxel Intersection Test Algorithm (3/3)

28 Ray Tracing Algorithm Image Raytrace (Camera cam, Scene scene, int width, int height) { Image image = new Image (width, height) ; for (int i = 0 ; i < height ; i++) for (int j = 0 ; j < width ; j++) { Ray ray = RayThruPixel (cam, i, j) ; Intersection hit = Intersect (ray, scene) ; image[i][j] = FindColor (hit) ; } return image ; }

29 Outgoing Radiance L o p, ω o = 2π + f r p, ω i, ω o L i p, ω i cos θ i d ωi BRDF

30 Outgoing Radiance L o p, ω o = 2π + f r p, ω i, ω o L i p, ω i cos θ i d ωi BRDF Outgoing Direction Incoming Direction

31 Monte Carlo Estimator I = a b f x dx Monte Carlo Estimator: I = b a n j=1 n f(x j )

32 Monte Carlo Importance Sampling Monte Carlo Estimator: I = b a n j=1 n f(x j ) p(x j )

33 Outgoing Radiance L o p, ω o = 2π + f r p, ω i, ω o L i p, ω i cos θ i d ωi L i p, ω i = L o r(p, ω i ), ω i L o p, ω o = 2π + f r p, ω i, ω o L o r(p, ω i ), ω i cos θ i d ωi

34 One Bounce is enough!

35 Real-Time Near-Field Single Bounce Indirect Light Generate RSM (Reflective Shadow Map) for fast near-field illumination Shoot N rays from x with maximum distance r Find first intersection point using binary voxelization Gather direct radiance from RSM

36 Real-Time Near-Field Single Bounce Indirect Light

37 Results (movie)

38 Results The effect of changing the voxel resolution 32x32x128 (47fps) 64x64x128 (36fps) 128x128x128 (25fps)

39 Results Voxel-Based Single Bounce illumination with different Radiuses R R = 1.5 (37 fps) R = center (27 fps) R = 4.0 right (21 fps)

40 Results 2 (Movie)

41 Thank you very much!!! :D

42 Questions?

43 References Reference Name TUM s Computer Graphics Course Slides 2013 Ray Tracing from Group Up, 2007 by AK Peters Ltd GPU Pro 3, 2012 by CRC Press An Approximate Global-Illumination System for Computer Generated Films Voxel-Based Global Illumination, Proceedings of ACM Symposium on Interactive 3D Graphics and Games 2011 (I3D'11) Voxel-Based Global Illumination slides at Computer Graphics and Image Processing Lab, SNU Author Prof. Westermann, TU-Munich Kevvin Suffern Wolfgang Engel Tabellion, E. And Lamorlette, A. Thiedemann, Henrich, Grosch, and Müller Jin Hur, Junhyuk Yoon