1 Shadows (2) ©Anthony Steed 2002. 2 Overview n Shadows – Umbra Recap n Penumbra Analytical v. Sampling n Analytical Aspect graphs Discontinuity meshing.

Slides:



Advertisements
Similar presentations
Exploration of advanced lighting and shading techniques
Advertisements

Parallax-Interpolated Shadow Map Occlusion
CS 352: Computer Graphics Chapter 7: The Rendering Pipeline.
Optimized Stencil Shadow Volumes
Optimized Stencil Shadow Volumes
Computer Graphics methods
The Art and Technology Behind Bioshock’s Special Effects
Week 10 - Monday.  What did we talk about last time?  Global illumination  Shadows  Projection shadows  Soft shadows.
Two Methods for Fast Ray-Cast Ambient Occlusion Samuli Laine and Tero Karras NVIDIA Research.
Introduction to 3D Graphics Lecture 5: From Realism to Real-Time Anthony Steed University College London.
Illumination Model & Surface-rendering Method 박 경 와.
Rasterization and Ray Tracing in Real-Time Applications (Games) Andrew Graff.
A Survey of Real-time Soft Shadows Algorithms Speaker: Alvin Date: 2003/7/23 EUROGRAPHICS 2003 J.-M. Hasenfratz, M. Lapierre, N. Holzschuch and F.X. Sillion.
Shadow Silhouette Maps Pradeep Sen, Mike Cammarano, Pat Hanrahan Stanford University.
A Real-Time Soft Shadow Volume Algorithm DTU Vision days Tomas Akenine-Möller Department of Computer Engineering Chalmers University of Technology Sweden
(conventional Cartesian reference system)
Shadow Algorithms Gerald Matzka Computer Science Seminar.
Approximate Soft Shadows on Arbitrary Surfaces using Penumbra Wedges Tomas Akenine-Möller Ulf Assarsson Department of Computer Engineering, Chalmers University.
Perspective Shadow Maps Marc Stamminger REVES/INRIA, Sophia-Antipolis, France now at: Bauhaus-Universität, Weimar, Germany George Drettakis REVES/INRIA,
©Larry F. Hodges (modified by Amos Johnson) 1 Shading Models.
Ever wonder how they made STAR WARS or TOY STORY? The development of Computer Graphics is responsible for a revolution in art and media. Starting with.
Introduction to 3D Graphics John E. Laird. Basic Issues u Given a internal model of a 3D world, with textures and light sources how do you project it.
Computer Graphics Shadows
09/18/03CS679 - Fall Copyright Univ. of Wisconsin Last Time Bump Mapping Multi-pass algorithms.
1 Occlusion Culling ©Yiorgos Chrysanthou, , Anthony Steed, 2004.
Shadows Computer Graphics. Shadows Shadows Extended light sources produce penumbras In real-time, we only use point light sources –Extended light sources.
Erdem Alpay Ala Nawaiseh. Why Shadows? Real world has shadows More control of the game’s feel  dramatic effects  spooky effects Without shadows the.
Computer Graphics Mirror and Shadows
Shadow No, not the Hank Marvin kind!. Go to: ows.html ows.html.
Shadow Algorithms Ikrima Elhassan.
Direct Illumination with Lazy Visibility Evaluation David Hart Philip Dutré Donald P. Greenberg Cornell University SIGGRAPH 99.
University of Illinois at Chicago Electronic Visualization Laboratory (EVL) CS 426 Intro to 3D Computer Graphics © 2003, 2004, 2005 Jason Leigh Electronic.
Technology and Historical Overview. Introduction to 3d Computer Graphics  3D computer graphics is the science, study, and method of projecting a mathematical.
1 Speeding Up Ray Tracing Images from Virtual Light Field Project ©Slides Anthony Steed 1999 & Mel Slater 2004.
The Visibility Problem In many environments, most of the primitives (triangles) are not visible most of the time –Architectural walkthroughs, Urban environments.
Interactive Rendering of Meso-structure Surface Details using Semi-transparent 3D Textures Vision, Modeling, Visualization Erlangen, Germany November 16-18,
CSC418 Computer Graphics n BSP tree n Z-Buffer n A-buffer n Scanline.
A Fast Shadow Algorithm for Area Light Sources Using Backprojection George Drettakis Eugene Fiume Department of Computer Science University of Toronto,
Computer Graphics The Rendering Pipeline - Review CO2409 Computer Graphics Week 15.
Shadows. Shadows is important in scenes, consolidating spatial relationships “Geometric shadows”: the shape of an area in shadow Early days, just pasted.
Collaborative Visual Computing Lab Department of Computer Science University of Cape Town Graphics Topics in VR By Shaun Nirenstein.
2 COEN Computer Graphics I Evening’s Goals n Discuss application bottleneck determination n Discuss various optimizations for making programs execute.
Real-time Graphics for VR Chapter 23. What is it about? In this part of the course we will look at how to render images given the constrains of VR: –we.
David Luebke11/26/2015 CS 551 / 645: Introductory Computer Graphics David Luebke
A survey of Light Source Detection Methods Nathan Funk University of Alberta Nov
- Laboratoire d'InfoRmatique en Image et Systèmes d'information
CS 325 Introduction to Computer Graphics 03 / 29 / 2010 Instructor: Michael Eckmann.
Ray Tracing Fall, Introduction Simple idea  Forward Mapping  Natural phenomenon infinite number of rays from light source to object to viewer.
1Ellen L. Walker 3D Vision Why? The world is 3D Not all useful information is readily available in 2D Why so hard? “Inverse problem”: one image = many.
1 Projection: Completing the Camera Model ©Yiorgos Chrysanthou 2001, Anthony Steed
Real-Time Dynamic Shadow Algorithms Evan Closson CSE 528.
Simplifying the Representation of Radiance from Multiple Emitters a George Drettakis iMAGIS/IMAG-INRIA Grenoble, FRANCE.
Shadows David Luebke University of Virginia. Shadows An important visual cue, traditionally hard to do in real-time rendering Outline: –Notation –Planar.
1 Shadow Rendering Techniques: Hard and Soft Author: Jamiur Rahman Supervisor: Mushfiqur Rouf Department of CSE BRAC University.
Render methods. Contents Levels of rendering Wireframe Plain shadow Gouraud Phong Comparison Gouraud-Phong.
Computer Vision Computer Vision based Hole Filling Chad Hantak COMP December 9, 2003.
09/23/03CS679 - Fall Copyright Univ. of Wisconsin Last Time Reflections Shadows Part 1 Stage 1 is in.
Real-Time Soft Shadows with Adaptive Light Source Sampling
Chapter 10 Computer Graphics
Combining Edges and Points for Interactive High-Quality Rendering
3D Graphics Rendering PPT By Ricardo Veguilla.
Hybrid Ray Tracing of Massive Models
Jim X. Chen George Mason University
© University of Wisconsin, CS559 Fall 2004
Chapter 14 Shading Models.
(c) 2002 University of Wisconsin
Real-time Rendering Shadow Maps
Real-Time Rendering Intro to Shadows
Monte Carlo I Previous lecture Analytical illumination formula
Chapter 14 Shading Models.
Presentation transcript:

1 Shadows (2) ©Anthony Steed 2002

2 Overview n Shadows – Umbra Recap n Penumbra Analytical v. Sampling n Analytical Aspect graphs Discontinuity meshing n Sampling Accumulation buffer Convolution

3 Shadows

4 Analytical v. Sampling n Analytical Find all boundaries within the penumbra. Done almost exclusively for polygonal light sources n Sampling Approximate solution that treat the light source as a set of points. Any shape source is possible.

5 Extremal Shadow Boundaries n What is the potential area of the penumbra and umbra? n For penumbra: Bounded by planes define by a pair of source vertex and occluder edge where the source is in the front space and the occluder on the back n For umbra: Similarly defined planes, but where source and occluder are in the back space

6 Extremal Shadow Boundaries

7 Shading Using Extremal Planes n If you write these planes into object space n We can use a scan-conversion as we have before At each pixel we must estimate the proportion of the light source that can be seen Usually done with SVBSP tree(s)

8 More Analysis n Borrowing aspect graphs from computer vision n Define critical surfaces where visual events occur EV surfaces: planes defined by edge and vertex EEE surfaces: quadratic surfaces defined by three non-adjacent edges. n Penumbra volumes so far have used EV only

9 EV and EEE Surfaces

10 Discontinuity Meshing n Discontinuities of the illumination of a polygon occur at the places where EV and EEE surfaces intersect the polygon n Discontinuities occur at different degrees n Discontinuities are written into the geometry of the scene as before

11 Shadows and Discontinuities

12 Storing the Discontinuity Mesh n DM-Tree which uses both 2D BSP tree and winged edge data structure

13 George Drettakis

14 George Drettakis

15 David Hedley

16 David Hedley

17 Sampling Methods n Model an area light source by multiple n point light sources n At rendering time render n times moving the light each time n Compose the image into an accumulation buffer

18 Accumulation Buffer n Yet another set of hardware buffers n Can be cleared (like the colour buffer) n You repeatedly copy the colour buffer to it, using a 1/N scale each time n After N iterations, the A-buffer holds the average of the N frames n Obviously requires precision! (Spend more $$)

19 Example

20 Recap n Penumbra is difficult to render correctly Boundaries are formed by very complex shapes n Discontinuity meshing is an analytical solution Difficult to implement n Sampling is obviously less accurate Potentially fast enough (soon) to do in real- time