# CPSC 314 LIGHTING AND SHADING

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 CPSC 314 LIGHTING AND SHADING UGRAD.CS.UBC.CA/~CS314 slide credits: Mikhail Bessmeltsev et al 1

2 THE RENDERING PIPELINE Vertices and attributes Vertex Shader Modelview transform Per-vertex attributes Vertex Post-Processing Viewport transform Clipping Rasterization Scan conversion Interpolation Fragment Shader Texturing/... Lighting/shading Per-Sample Operations Depth test Framebuffer Blending 2

3 LIGHTING/SHADING Goal Model the interaction of light with surfaces to render realistic images Generate per (pixel/vertex) color 3

4 FACTORS Light sources Location, type & color Surface materials How surfaces reflect light Transport of light How light moves in a scene Viewer position 4

5 FACTORS Light sources Location, type & color Surface materials How surfaces reflect light Transport of light How light moves in a scene Viewer position How can we do this in the pipeline? 5

6 ILLUMINATION MODELS/ALGORITHMS Local illumination - Fast Ignore real physics, approximate the look Interaction of each object with light Compute on surface (light to viewer) Global illumination Slow Physically based Interactions between objects 6

7 THE BIG PICTURE (BASIC) Light: energy in a range of wavelengths White light all wavelengths Colored (e.g. red) subset of wavelengths Surface color reflected wavelength White reflects all lengths Black absorbs everything Colored (e.g. red) absorbs all but the reflected color Multiple light sources add (energy sums) 7

8 MATERIALS Surface reflectance: Illuminate surface point with a ray of light from different directions How much light is reflected in each direction? 8

9 BASIC TYPES 9

10 REFLECTANCE DISTRIBUTION MODEL Most surfaces exhibit complex reflectances Vary with incident and reflected directions. Model with combination known as BRDF BRDF: Bidirectional Reflectance Distribution Function + + = 10

11 BRDF MEASUREMENTS/PLOTS 2D slice 11

13 SURFACE ROUGHNESS notice another effect of roughness: each microfacet is treated as a perfect mirror. incident light reflected in different directions by different facets. end result is mixed reflectance. smoother surfaces are more specular or glossy. random distribution of facet normals results in diffuse reflectance. 13

14 PHYSICS OF DIFFUSE REFLECTION ideal diffuse reflection very rough surface at the microscopic level real-world example: chalk microscopic variations mean incoming ray of light equally likely to be reflected in any direction over the hemisphere what does the reflected intensity depend on? 14

15 LAMBERT S COSINE LAW ideal diffuse surface reflection the energy reflected by a small portion of a surface from a light source in a given direction is proportional to the cosine of the angle between that direction and the surface normal reflected intensity independent of viewing direction depends on surface orientation wrt light often called Lambertian surfaces 15

16 DIFFUSE (LAMBERT) Intuitively: cross-sectional area of the beam intersecting an element of surface area is smaller for greater angles with the normal. 16

17 COMPUTING DIFFUSE REFLECTION Depends on angle of incidence: angle between surface normal and incoming light I diffuse = k d I light cos θ In practice use vector arithmetic I diffuse = k d I light (n l) l θ n Scalar (B/W intensity) or 3-tuple (color) k d : diffuse coefficient, surface color I light : incoming light intensity I diffuse : outgoing light intensity (for diffuse reflection) NB: Always normalize vectors used in lighting!! n, l should be unit vectors 17

18 DIFFUSE LIGHTING EXAMPLES Lambertian sphere from several lighting angles: need only consider angles from 0 to 90 18

19 DIFFUSE INTERREFLECTION 19

20 SPECULAR HIGHLIGHTS Michiel van de Panne 20

21 PHYSICS OF SPECULAR REFLECTION Geometry of specular (perfect mirror) reflection Snell s law special case: Law of Reflection n l (n l)n r = -l+2(n l)n α α -l 21

22 PHYSICS OF SPECULAR REFLECTION Geometry of specular (perfect mirror) reflection Snell s law special case: Law of Reflection In GLSL: use reflect(-l,n) n l (n l)n r = -l+2(n l)n α α -l 22

23 CALCULATING R VECTOR P = N cos θ L N projection of L onto N P = N cos θ L, N are unit length P = N ( N L ) 2 P = R + L 2 P L = R 2 (N ( N L )) - L = R L N θ P P L R 23

24 EMPIRICAL APPROXIMATION Snell s law = perfect mirror-like surfaces But.. few surfaces exhibit perfect specularity Gaze and reflection directions never EXACTLY coincide Expect most reflected light to travel in direction predicted by Snell s Law But some light may be reflected in a direction slightly off the ideal reflected ray As angle from ideal reflected ray increases, we expect less light to be reflected 24

25 EMPIRICAL APPROXIMATION Angular falloff How to model this falloff? 25

26 PHONG LIGHTING Most common lighting model in computer graphics (Phong Bui-Tuong, 1975) I specular = k s I light (cosφ) n s I specular = k s I light (v r) n s ϕ: angle between r and view direction v n s : purely empirical constant, varies rate of falloff k s : specular coefficient, highlight color no physical basis, plastic look 26 reminder: normalize all vectors: n,l,r,v v

27 PHONG EXAMPLES varying light position varying n s 27

28 ALTERNATIVE MODEL Blinn-Phong model (Jim Blinn, 1977) Variation with better physical interpretation h: halfway vector; r: roughness I specular = ks light 1/ r ( h n) I ; with h = ( l + v) / 2 l h n v α α 28

29 Light is linear If multiple rays illuminate the surface point the result is just the sum of the individual reflections for each ray MULTIPLE LIGHTS ) ) ( ) ( ( n p s p d p p v r k l n k I + 29

30 AMBIENT LIGHT Non-directional light environment light Object illuminated with same light everywhere Looks like silhouette Illumination equation I = I a k a I a - ambient light intensity - fraction of this light reflected from surface k a 30

31 LIGHT SOURCES ambient lights no identifiable source or direction hack for replacing true global illumination (diffuse interreflection: light bouncing off from other objects) 31

32 ILLUMINATION EQUATION (PHONG) If we take the previous formula and add ambient component: I a k a + I p (k d (n l p )+ k s (r p v) n ) p 32

33 LIGHT Light has color Interacts with object color (r,g,b) I = I k, I, I, k, I, I, k Blue light on white surface? Blue light on red surface? I k I a a a = ( I = ( k = ( I r a ar ar g ag ag b ) ab ab ) ) = ( I ar k ar, I ag k ag, I ab k ab ) 33

34 LIGHT AND MATERIAL SPECIFICATION Light source: amount of RGB light emitted value = intensity per channel e.g., (1.0,0.5,0.5) every light source emits ambient, diffuse, and specular light Materials: amount of RGB light reflected value represents percentage reflected e.g., (0.0,1.0,0.5) Interaction: multiply components Red light (1,0,0) x green surface (0,1,0) = black (0,0,0) 34

35 WHITEBOARD EXAMPLE 35

36 WHITEBOARD EXAMPLE 36

37 LIGHT SOURCE TYPES Point Light light originates at a point Directional Light (point light at infinity) light rays are parallel Rays hit a planar surface at identical angles Spot Light point light with limited angles 37

38 LIGHT SOURCE TYPES Point Light light originates at a point defined by location only Directional Light (point light at infinity) light rays are parallel Rays hit a planar surface at identical angles defined by direction only Spot Light point light with limited angles defined by location, direction, and angle range 38

39 LIGHT SOURCES area lights light sources with a finite area more realistic model of many light sources much more complex! 39

40 WHICH LIGHTS/MATERIALS ARE USED HERE? 40

41 LIGHT SOURCE FALLOFF Quadratic falloff (point- and spot lights) Brightness of objects depends on power per unit area that hits the object The power per unit area for a point or spot light decreases quadratically with distance Area 4πr 2 Area 4π(2r) 2 41

42 For multiple light sources: - distance between surface and light source + distance between surface and viewer, A attenuation function ILLUMINATION EQUATION WITH ATTENUATION ) ) ( ) ( ( ) ( n p s p d p p p a a v r k l n k d A I k I I + + = d p 42

43 WHEN TO APPLY LIGHTING MODEL? per polygon flat shading per vertex Gouraud shading per pixel per pixel lighting Phong shading Image Intergraph Computer Systems 43

44 LIGHTING VS. SHADING lighting process of computing the luminous intensity (i.e., outgoing light) at a particular 3-D point, usually on a surface shading the process of assigning colors to pixels (why the distinction?) 44

45 APPLYING ILLUMINATION we now have an illumination model for a point on a surface if surface defined as mesh of polygonal facets, which points should we use? fairly expensive calculation several possible answers, each with different implications for visual quality of result 45

46 APPLYING ILLUMINATION polygonal/triangular models each facet has a constant surface normal if light is directional, diffuse reflectance is constant across the facet why? 46

47 FLAT SHADING simplest approach calculates illumination at a single point for each polygon obviously inaccurate for smooth surfaces 47

48 FLAT SHADING APPROXIMATIONS if an object really is faceted, is this accurate? no! for point sources, the direction to light varies across the facet for specular reflectance, direction to eye varies across the facet 48

49 IMPROVING FLAT SHADING what if evaluate Phong lighting model at each pixel of the polygon? better, but result still clearly faceted for smoother-looking surfaces we introduce vertex normals at each vertex usually different from facet normal used only for shading think of as a better approximation of the real surface that the polygons approximate 49

50 VERTEX NORMALS vertex normals may be provided with the model computed from first principles approximated by averaging the normals of the facets that share the vertex 50

51 GOURAUD SHADING most common approach perform Phong lighting at the vertices linearly interpolate the resulting colors over faces along edges along scanlines edge: mix of c 1, c 2 C 1 does this eliminate the facets? C 3 interior: mix of c1, c2, c3 C 2 edge: mix of c1, c3 51

52 GOURAUD SHADING ARTIFACTS often appears dull, chalky lacks accurate specular component if included, will be averaged over entire polygon C 1 C 1 C 3 C 3 C 2 this interior shading missed! C 2 this vertex shading spread over too much area 52

53 GOURAUD SHADING ARTIFACTS Mach bands eye enhances discontinuity in first derivative very disturbing, especially for highlights 53

54 GOURAUD SHADING ARTIFACTS Mach bands C 1 C 4 C 3 C 2 Discon;nuity in rate of color change occurs here 54

55 GOURAUD SHADING ARTIFACTS perspective transformations affine combinations only invariant under affine, not under perspective transformations thus, perspective projection alters the linear interpolation! Image plane Z into the scene 55

56 GOURAUD SHADING ARTIFACTS perspective transformation problem colors slightly swim on the surface as objects move relative to the camera usually ignored since often only small difference usually smaller than changes from lighting variations to do it right either shading in object space or correction for perspective foreshortening expensive thus hardly ever done for colors 56

57 PHONG SHADING linearly interpolating surface normal across the facet, applying Phong lighting model at every pixel same input as Gouraud shading pro: much smoother results con: considerably more expensive not the same as Phong lighting common confusion Phong lighting: empirical model to calculate illumination at a point on a surface 57

58 PHONG SHADING linearly interpolate the vertex normals compute lighting equations at each pixel can use specular component N 1 # lights i=1 I total = k a I ambient + I i k d n l i ( ( ) + k s ( v r i ) n ) shiny remember: normals used in diffuse and specular terms N 4 N 2 N 3 disconenuity in normal s rate of change harder to detect 58

59 PHONG SHADING DIFFICULTIES more computationally expensive per-pixel vector normalization and lighting computation! floating point operations required straightforward with shaders lighting after perspective projection messes up the angles between vectors have to keep eye-space vectors around 59

60 SHADING ARTIFACTS: SILHOUETTES polygonal silhouettes remain Gouraud Phong 60

61 SHADING ARTIFACTS: ORIENTATION interpolation dependent on polygon orientation view dependence! A B D Rotate - 90 o and color same point C B i! A C Interpolate between AB and AD D Interpolate between CD and AD 61

62 Shading Ar+facts: Shared Ver+ces D C H vertex B shared by two rectangles on the right, but not by the one on the leo B G first poreon of the scanline is interpolated between DE and AC E A F second poreon of the scanline is interpolated between BC and GH a large disconenuity could arise 62

63 SHADING MODELS SUMMARY flat shading compute Phong lighting once for entire polygon Gouraud shading compute Phong lighting at the vertices and interpolate lighting values across polygon Phong shading compute averaged vertex normals interpolate normals across polygon and perform Phong lighting across polygon 63

67 NON-PHOTOREALISTIC SHADING cool-to-warm shading k w = 1+ n l 2,c = k w c w + (1 k w )c c 67

68 NON-PHOTOREALISTIC SHADING draw silhouettes: if draw creases: if (e n 0 )(e n 1 ) 0 (n 0 n 1 ) threshold, e=edge-eye vector 68

### Lighting/Shading II. Week 7, Mon Mar 1

University of British Columbia CPSC 314 Computer Graphics Jan-Apr 2010 Tamara Munzner Lighting/Shading II Week 7, Mon Mar 1 http://www.ugrad.cs.ubc.ca/~cs314/vjan2010 News Homework 3 out today Homework

### CS5620 Intro to Computer Graphics

So Far wireframe hidden surfaces Next step 1 2 Light! Need to understand: How lighting works Types of lights Types of surfaces How shading works Shading algorithms What s Missing? Lighting vs. Shading

### Topic 9: Lighting & Reflection models 9/10/2016. Spot the differences. Terminology. Two Components of Illumination. Ambient Light Source

Topic 9: Lighting & Reflection models Lighting & reflection The Phong reflection model diffuse component ambient component specular component Spot the differences Terminology Illumination The transport

### Computer Graphics. Illumination and Shading

() Illumination and Shading Dr. Ayman Eldeib Lighting So given a 3-D triangle and a 3-D viewpoint, we can set the right pixels But what color should those pixels be? If we re attempting to create a realistic

Illumination and Shading Computer Graphics COMP 770 (236) Spring 2007 Instructor: Brandon Lloyd 2/14/07 1 From last time Texture mapping overview notation wrapping Perspective-correct interpolation Texture

Illumination and Shading Illumination (Lighting)! Model the interaction of light with surface points to determine their final color and brightness! The illumination can be computed either at vertices or

### Computer Graphics. Shading. Based on slides by Dianna Xu, Bryn Mawr College

Computer Graphics Shading Based on slides by Dianna Xu, Bryn Mawr College Image Synthesis and Shading Perception of 3D Objects Displays almost always 2 dimensional. Depth cues needed to restore the third

Illumination & Shading Goals Introduce the types of light-material interactions Build a simple reflection model---the Phong model--- that can be used with real time graphics hardware Why we need Illumination

### CSE 167: Lecture #7: Color and Shading. Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2011

CSE 167: Introduction to Computer Graphics Lecture #7: Color and Shading Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2011 Announcements Homework project #3 due this Friday,

### ECS 175 COMPUTER GRAPHICS. Ken Joy.! Winter 2014

ECS 175 COMPUTER GRAPHICS Ken Joy Winter 2014 Shading To be able to model shading, we simplify Uniform Media no scattering of light Opaque Objects No Interreflection Point Light Sources RGB Color (eliminating

### CS Illumination and Shading. Slide 1

CS 112 - Illumination and Shading Slide 1 Illumination/Lighting Interaction between light and surfaces Physics of optics and thermal radiation Very complex: Light bounces off several surface before reaching

### Comp 410/510 Computer Graphics. Spring Shading

Comp 410/510 Computer Graphics Spring 2017 Shading Why we need shading Suppose we build a model of a sphere using many polygons and then color it using a fixed color. We get something like But we rather

Illumination and Shading Illumination and Shading z Illumination Models y Ambient y Diffuse y Attenuation y Specular Reflection z Interpolated Shading Models y Flat, Gouraud, Phong y Problems CS4451: Fall

### Lighting affects appearance

Lighting affects appearance 1 Source emits photons Light And then some reach the eye/camera. Photons travel in a straight line When they hit an object they: bounce off in a new direction or are absorbed

### CSE 681 Illumination and Phong Shading

CSE 681 Illumination and Phong Shading Physics tells us What is Light? We don t see objects, we see light reflected off of objects Light is a particle and a wave The frequency of light What is Color? Our

Shading and Illumination OpenGL Shading Without Shading With Shading Physics Bidirectional Reflectance Distribution Function (BRDF) f r (ω i,ω ) = dl(ω ) L(ω i )cosθ i dω i = dl(ω ) L(ω i )( ω i n)dω

### Introduction to Computer Graphics. Farhana Bandukwala, PhD Lecture 14: Light Interacting with Surfaces

Introduction to Computer Graphics Farhana Bandukwala, PhD Lecture 14: Light Interacting with Surfaces Outline Computational tools Reflection models Polygon shading Computation tools Surface normals Vector

### surface: reflectance transparency, opacity, translucency orientation illumination: location intensity wavelength point-source, diffuse source

walters@buffalo.edu CSE 480/580 Lecture 18 Slide 1 Illumination and Shading Light reflected from nonluminous objects depends on: surface: reflectance transparency, opacity, translucency orientation illumination:

### CS 5625 Lec 2: Shading Models

CS 5625 Lec 2: Shading Models Kavita Bala Spring 2013 Shading Models Chapter 7 Next few weeks Textures Graphics Pipeline Light Emission To compute images What are the light sources? Light Propagation Fog/Clear?

### Interpolation using scanline algorithm

Interpolation using scanline algorithm Idea: Exploit knowledge about already computed color values. Traverse projected triangle top-down using scanline. Compute start and end color value of each pixel

### Raytracing CS148 AS3. Due :59pm PDT

Raytracing CS148 AS3 Due 2010-07-25 11:59pm PDT We start our exploration of Rendering - the process of converting a high-level object-based description of scene into an image. We will do this by building

Illumination and Shading Light sources emit intensity: assigns intensity to each wavelength of light Humans perceive as a colour - navy blue, light green, etc. Exeriments show that there are distinct I

### Turn on the Lights: Reflectance

Turn on the Lights: Reflectance Part 2: Shading Tuesday, October 15 2012 Lecture #14 Goal of Shading Model simple light sources Point light sources Extended light sources Ambient lighting Model lighting

### CMSC427 Advanced shading getting global illumination by local methods. Credit: slides Prof. Zwicker

CMSC427 Advanced shading getting global illumination by local methods Credit: slides Prof. Zwicker Topics Shadows Environment maps Reflection mapping Irradiance environment maps Ambient occlusion Reflection

### Orthogonal Projection Matrices. Angel and Shreiner: Interactive Computer Graphics 7E Addison-Wesley 2015

Orthogonal Projection Matrices 1 Objectives Derive the projection matrices used for standard orthogonal projections Introduce oblique projections Introduce projection normalization 2 Normalization Rather

### How do we draw a picture?

1 How do we draw a picture? Define geometry. Now what? We can draw the edges of the faces. Wireframe. We can only draw the edges of faces that are visible. We can fill in the faces. Giving each object

### Lighting affects appearance

Lighting affects appearance 1 Source emits photons Light And then some reach the eye/camera. Photons travel in a straight line When they hit an object they: bounce off in a new direction or are absorbed

### Three-Dimensional Graphics V. Guoying Zhao 1 / 55

Computer Graphics Three-Dimensional Graphics V Guoying Zhao 1 / 55 Shading Guoying Zhao 2 / 55 Objectives Learn to shade objects so their images appear three-dimensional Introduce the types of light-material

### Illumination. Illumination CMSC 435/634

Illumination CMSC 435/634 Illumination Interpolation Illumination Illumination Interpolation Illumination Illumination Effect of light on objects Mostly look just at intensity Apply to each color channel

### CEng 477 Introduction to Computer Graphics Fall

Illumination Models and Surface-Rendering Methods CEng 477 Introduction to Computer Graphics Fall 2007 2008 Illumination Models and Surface Rendering Methods In order to achieve realism in computer generated

Lessons Learned from HW Shading CS Interactive Computer Graphics Prof. David E. Breen Department of Computer Science Only have an idle() function if something is animated Set idle function to NULL, when

### Rendering Light Reflection Models

Rendering Light Reflection Models Visual Imaging in the Electronic Age Donald P. Greenberg October 3, 2017 Lecture #13 Program of Computer Graphics, Cornell University General Electric - 167 Cornell in

### CENG 477 Introduction to Computer Graphics. Ray Tracing: Shading

CENG 477 Introduction to Computer Graphics Ray Tracing: Shading Last Week Until now we learned: How to create the primary rays from the given camera and image plane parameters How to intersect these rays

### The Rasterization Pipeline

Lecture 5: The Rasterization Pipeline Computer Graphics and Imaging UC Berkeley CS184/284A, Spring 2016 What We ve Covered So Far z x y z x y (0, 0) (w, h) Position objects and the camera in the world

### The Rasterization Pipeline

Lecture 5: The Rasterization Pipeline Computer Graphics and Imaging UC Berkeley What We ve Covered So Far z x y z x y (0, 0) (w, h) Position objects and the camera in the world Compute position of objects

### Shading, lighting, & BRDF Theory. Cliff Lindsay, PHD

Shading, lighting, & BRDF Theory Cliff Lindsay, PHD Overview of today s lecture BRDF Characteristics Lights in terms of BRDFs Classes of BRDFs Ambient light & Shadows in terms of BRDFs Decomposing Reflection

### Deferred Rendering Due: Wednesday November 15 at 10pm

CMSC 23700 Autumn 2017 Introduction to Computer Graphics Project 4 November 2, 2017 Deferred Rendering Due: Wednesday November 15 at 10pm 1 Summary This assignment uses the same application architecture

### Illumination and Shading ECE 567

CS 543: Computer Graphics Illumination & Shading I Robert W. Lindeman Associate Professor Interactive Media & Game Development Department of Computer Science Worcester Polytechnic Institute gogo@wpi.edu

### Surface Reflection Models

Surface Reflection Models Frank Losasso (flosasso@nvidia.com) Introduction One of the fundamental topics in lighting is how the light interacts with the environment. The academic community has researched

### Lighting and Shading Computer Graphics I Lecture 7. Light Sources Phong Illumination Model Normal Vectors [Angel, Ch

15-462 Computer Graphics I Lecture 7 Lighting and Shading February 12, 2002 Frank Pfenning Carnegie Mellon University http://www.cs.cmu.edu/~fp/courses/graphics/ Light Sources Phong Illumination Model

DH2323 DGI15 INTRODUCTION TO COMPUTER GRAPHICS AND INTERACTION LIGHTING AND SHADING Christopher Peters HPCViz, KTH Royal Institute of Technology, Sweden chpeters@kth.se http://kth.academia.edu/christopheredwardpeters

### Lighting and Shading. Slides: Tamar Shinar, Victor Zordon

Lighting and Shading Slides: Tamar Shinar, Victor Zordon Why we need shading Suppose we build a model of a sphere using many polygons and color each the same color. We get something like But we want 2

### Lets assume each object has a defined colour. Hence our illumination model is looks unrealistic.

Shading Models There are two main types of rendering that we cover, polygon rendering ray tracing Polygon rendering is used to apply illumination models to polygons, whereas ray tracing applies to arbitrary

### So far, we have considered only local models of illumination; they only account for incident light coming directly from the light sources.

11 11.1 Basics So far, we have considered only local models of illumination; they only account for incident light coming directly from the light sources. Global models include incident light that arrives

### 03 RENDERING PART TWO

03 RENDERING PART TWO WHAT WE HAVE SO FAR: GEOMETRY AFTER TRANSFORMATION AND SOME BASIC CLIPPING / CULLING TEXTURES AND MAPPING MATERIAL VISUALLY DISTINGUISHES 2 OBJECTS WITH IDENTICAL GEOMETRY FOR NOW,

### Computer Graphics. Lecture 13. Global Illumination 1: Ray Tracing and Radiosity. Taku Komura

Computer Graphics Lecture 13 Global Illumination 1: Ray Tracing and Radiosity Taku Komura 1 Rendering techniques Can be classified as Local Illumination techniques Global Illumination techniques Local

### Computer Graphics. Lecture 10. Global Illumination 1: Ray Tracing and Radiosity. Taku Komura 12/03/15

Computer Graphics Lecture 10 Global Illumination 1: Ray Tracing and Radiosity Taku Komura 1 Rendering techniques Can be classified as Local Illumination techniques Global Illumination techniques Local

### Light Sources. Spotlight model

lecture 12 Light Sources sunlight (parallel) Sunny day model : "point source at infinity" - lighting - materials: diffuse, specular, ambient spotlight - shading: Flat vs. Gouraud vs Phong light bulb ambient

### Illumination Models and Surface-Rendering Methods. Chapter 10

Illumination Models and Surface-Rendering Methods Chapter 10 Illumination and Surface- Rendering Given scene specifications object positions, optical properties of the surface, viewer position, viewing

### Rendering Algorithms: Real-time indirect illumination. Spring 2010 Matthias Zwicker

Rendering Algorithms: Real-time indirect illumination Spring 2010 Matthias Zwicker Today Real-time indirect illumination Ray tracing vs. Rasterization Screen space techniques Visibility & shadows Instant

### Chapter 17: The Truth about Normals

Chapter 17: The Truth about Normals What are Normals? When I first started with Blender I read about normals everywhere, but all I knew about them was: If there are weird black spots on your object, go

Illumination and Shading Illumination (Lighting) Model the interaction of light with surface points to determine their final color and brightness OpenGL computes illumination at vertices illumination Shading

### CGT520 Lighting. Lighting. T-vertices. Normal vector. Color of an object can be specified 1) Explicitly as a color buffer

CGT520 Lighting Lighting Color of an object can be specified 1) Explicitly as a color buffer Bedrich Benes, Ph.D. Purdue University Department of Computer Graphics 2) Implicitly from the illumination model.

Objectives Shading in OpenGL Introduce the OpenGL shading methods - per vertex shading vs per fragment shading - Where to carry out Discuss polygonal shading - Flat - Smooth - Gouraud CITS3003 Graphics

Shaders Oscar 1/43 Apodaca and Gritz, Advanced RenderMan Pixel Color Irradiance measures the power per unit area hitting a pixel E = න L i cos θ i dω i (obtained by integrating an equation form last class)

Why we need shading? Suppose we build a model of a sphere using many polygons and color it with glcolor. We get something like But we want Light-material interactions cause each point to have a different

Computer Graphics (Fall 2008) COMS 4160, Lecture 19: Illumination and Shading 2 http://www.cs.columbia.edu/~cs4160 Radiance Power per unit projected area perpendicular to the ray per unit solid angle in

### Shading , Fall 2004 Nancy Pollard Mark Tomczak

15-462, Fall 2004 Nancy Pollard Mark Tomczak Shading Shading Concepts Shading Equations Lambertian, Gouraud shading Phong Illumination Model Non-photorealistic rendering [Shirly, Ch. 8] Announcements Written

### Methodology for Lecture. Importance of Lighting. Outline. Shading Models. Brief primer on Color. Foundations of Computer Graphics (Spring 2010)

Foundations of Computer Graphics (Spring 2010) CS 184, Lecture 11: OpenGL 3 http://inst.eecs.berkeley.edu/~cs184 Methodology for Lecture Lecture deals with lighting (teapot shaded as in HW1) Some Nate

### Color and Light. CSCI 4229/5229 Computer Graphics Summer 2008

Color and Light CSCI 4229/5229 Computer Graphics Summer 2008 Solar Spectrum Human Trichromatic Color Perception Are A and B the same? Color perception is relative Transmission,Absorption&Reflection Light

### - Rasterization. Geometry. Scan Conversion. Rasterization

Computer Graphics - The graphics pipeline - Geometry Modelview Geometry Processing Lighting Perspective Clipping Scan Conversion Texturing Fragment Tests Blending Framebuffer Fragment Processing - So far,

### CSE 167: Lecture #8: GLSL. Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2012

CSE 167: Introduction to Computer Graphics Lecture #8: GLSL Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2012 Announcements Homework project #4 due Friday, November 2 nd Introduction:

### Ø Sampling Theory" Ø Fourier Analysis Ø Anti-aliasing Ø Supersampling Strategies" Ø The Hall illumination model. Ø Original ray tracing paper

CS 431/636 Advanced Rendering Techniques Ø Dr. David Breen Ø Korman 105D Ø Wednesday 6PM 8:50PM Presentation 6 5/16/12 Questions from ast Time? Ø Sampling Theory" Ø Fourier Analysis Ø Anti-aliasing Ø Supersampling

### graphics pipeline computer graphics graphics pipeline 2009 fabio pellacini 1

graphics pipeline computer graphics graphics pipeline 2009 fabio pellacini 1 graphics pipeline sequence of operations to generate an image using object-order processing primitives processed one-at-a-time

### rendering equation computer graphics rendering equation 2009 fabio pellacini 1

rendering equation computer graphics rendering equation 2009 fabio pellacini 1 physically-based rendering synthesis algorithms that compute images by simulation the physical behavior of light computer

### Surface Graphics. 200 polys 1,000 polys 15,000 polys. an empty foot. - a mesh of spline patches:

Surface Graphics Objects are explicitely defined by a surface or boundary representation (explicit inside vs outside) This boundary representation can be given by: - a mesh of polygons: 200 polys 1,000

### Summary. What is Computer Graphics? IRISA 2. Coordinate systems. 4. Geometric transformations for display

Summary Basic Computer Graphics Kadi Bouatouch IRISA Email: kadi@irisa.fr 1. Introduction 2. Coordinate systems 3. Geometric transformations 4. Geometric transformations for display 5. Choosing the camera

### Classic Rendering Pipeline

CS580: Classic Rendering Pipeline Sung-Eui Yoon ( 윤성의 ) Course URL: http://sglab.kaist.ac.kr/~sungeui/gcg/ Course Objectives Understand classic rendering pipeline Just high-level concepts, not all the

### CSE 167: Lecture #8: Lighting. Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2011

CSE 167: Introduction to Computer Graphics Lecture #8: Lighting Jürgen P. Schulze, Ph.D. University of California, San Diego Fall Quarter 2011 Announcements Homework project #4 due Friday, October 28 Introduction:

### Computer Graphics 1. Chapter 7 (June 17th, 2010, 2-4pm): Shading and rendering. LMU München Medieninformatik Andreas Butz Computergraphik 1 SS2010

Computer Graphics 1 Chapter 7 (June 17th, 2010, 2-4pm): Shading and rendering 1 The 3D rendering pipeline (our version for this class) 3D models in model coordinates 3D models in world coordinates 2D Polygons

### Lecture 4: Reflection Models

Lecture 4: Reflection Models CS 660, Spring 009 Kavita Bala Computer Science Cornell University Outline Light sources Light source characteristics Types of sources Light reflection Physics-based models

Last Time? The Traditional Graphics Pipeline Reading for Today A Practical Model for Subsurface Light Transport, Jensen, Marschner, Levoy, & Hanrahan, SIGGRAPH 2001 Participating Media Measuring BRDFs

### Wednesday, 26 January 2005, 14:OO - 17:OO h.

Delft University of Technology Faculty Electrical Engineering, Mathematics, and Computer Science Mekelweg 4, Delft TU Delft Examination for Course IN41 5 1-3D Computer Graphics and Virtual Reality Please

### Lecture outline Graphics and Interaction Surface rendering and shading. Shading techniques. Introduction. Surface rendering and shading

Lecture outline 433-324 Graphics and Interaction Surface rendering and shading Department of Computer Science and Software Engineering The Introduction Surface rendering and shading Gouraud shading Phong

### Chapter 4- Blender Render Engines

Chapter 4- Render Engines What is a Render Engine? As you make your 3D models in, your goal will probably be to generate (render) an image or a movie as a final result. The software that determines how

### COMP environment mapping Mar. 12, r = 2n(n v) v

Rendering mirror surfaces The next texture mapping method assumes we have a mirror surface, or at least a reflectance function that contains a mirror component. Examples might be a car window or hood,

### Computergrafik. Matthias Zwicker Universität Bern Herbst 2016

Computergrafik Matthias Zwicker Universität Bern Herbst 2016 Today More shading Environment maps Reflection mapping Irradiance environment maps Ambient occlusion Reflection and refraction Toon shading

### Lecture 17: Recursive Ray Tracing. Where is the way where light dwelleth? Job 38:19

Lecture 17: Recursive Ray Tracing Where is the way where light dwelleth? Job 38:19 1. Raster Graphics Typical graphics terminals today are raster displays. A raster display renders a picture scan line

### Computer Graphics I. Assignment 3

UNIVERSITÄT DES SAARLANDES Dr.-Ing. Hendrik P.A. Lensch Max Planck Institut Informatik Art Tevs (tevs@mpi-inf.mpg.de) Boris Ajdin (bajdin@mpi-inf.mpg.de) Matthias Hullin (hullin@mpi-inf.mpg.de) 12. November

### Basic Computer Graphics. Kadi Bouatouch IRISA

Basic Computer Graphics Kadi Bouatouch IRISA Email: kadi@irisa.fr 1 Summary 1. Introduction 2. Coordinate systems 3. Geometric transformations 4. Geometric transformations for display 5. Choosing the camera

### CS452/552; EE465/505. Lighting & Shading

CS452/552; EE465/505 Lighting & Shading 2-17 15 Outline! More on Lighting and Shading Read: Angel Chapter 6 Lab2: due tonight use ASDW to move a 2D shape around; 1 to center Local Illumination! Approximate

### SEOUL NATIONAL UNIVERSITY

Fashion Technology 5. 3D Garment CAD-1 Sungmin Kim SEOUL NATIONAL UNIVERSITY Overview Design Process Concept Design Scalable vector graphics Feature-based design Pattern Design 2D Parametric design 3D

### CS 4620 Midterm, March 21, 2017

CS 460 Midterm, March 1, 017 This 90-minute exam has 4 questions worth a total of 100 points. Use the back of the pages if you need more space. Academic Integrity is expected of all students of Cornell

### Introduction to 3D Graphics

Introduction to 3D Graphics Using OpenGL 3D 1/46 Classical Polygon Graphics (H/W) Pipeline Mesh objects with 3D polygons (triangles or quads usually) Apply material properties to each object (for reflectance

### Computer Graphics. Lecture 9 Environment mapping, Mirroring

Computer Graphics Lecture 9 Environment mapping, Mirroring Today Environment Mapping Introduction Cubic mapping Sphere mapping refractive mapping Mirroring Introduction reflection first stencil buffer

### Announcement. Lighting and Photometric Stereo. Computer Vision I. Surface Reflectance Models. Lambertian (Diffuse) Surface.

Lighting and Photometric Stereo CSE252A Lecture 7 Announcement Read Chapter 2 of Forsyth & Ponce Might find section 12.1.3 of Forsyth & Ponce useful. HW Problem Emitted radiance in direction f r for incident

### Photorealism: Ray Tracing

Photorealism: Ray Tracing Reading Assignment: Chapter 13 Local vs. Global Illumination Local Illumination depends on local object and light sources only Global Illumination at a point can depend on any

### CSE 690: GPGPU. Lecture 2: Understanding the Fabric - Intro to Graphics. Klaus Mueller Stony Brook University Computer Science Department

CSE 690: GPGPU Lecture 2: Understanding the Fabric - Intro to Graphics Klaus Mueller Stony Brook University Computer Science Department Klaus Mueller, Stony Brook 2005 1 Surface Graphics Objects are explicitely

### Ray Tracing. CSCI 420 Computer Graphics Lecture 15. Ray Casting Shadow Rays Reflection and Transmission [Ch ]

CSCI 420 Computer Graphics Lecture 15 Ray Tracing Ray Casting Shadow Rays Reflection and Transmission [Ch. 13.2-13.3] Jernej Barbic University of Southern California 1 Local Illumination Object illuminations

### C P S C 314 S H A D E R S, O P E N G L, & J S RENDERING PIPELINE. Mikhail Bessmeltsev

C P S C 314 S H A D E R S, O P E N G L, & J S RENDERING PIPELINE UGRAD.CS.UBC.C A/~CS314 Mikhail Bessmeltsev 1 WHAT IS RENDERING? Generating image from a 3D scene 2 WHAT IS RENDERING? Generating image

### Ambient reflection. Jacobs University Visualization and Computer Graphics Lab : Graphics and Visualization 407

Ambient reflection Phong reflection is a local illumination model. It only considers the reflection of light that directly comes from the light source. It does not compute secondary reflection of light

### Recall: Basic Ray Tracer

1 Recall: Ray Tracing Generate an image by backwards tracing the path of light through pixels on an image plane Simulate the interaction of light with objects Recall: Basic Ray Tracer Trace a primary ray

### Objectives. Shading II. Distance Terms. The Phong Reflection Model

Shading II Objectives Introduce distance terms to the shading model. More details about the Phong model (lightmaterial interaction). Introduce the Blinn lighting model (also known as the modified Phong

### 6.837 Introduction to Computer Graphics Assignment 5: OpenGL and Solid Textures Due Wednesday October 22, 2003 at 11:59pm

6.837 Introduction to Computer Graphics Assignment 5: OpenGL and Solid Textures Due Wednesday October 22, 2003 at 11:59pm In this assignment, you will add an interactive preview of the scene and solid

### Global Illumination. Global Illumination. Direct Illumination vs. Global Illumination. Indirect Illumination. Soft Shadows.

CSCI 480 Computer Graphics Lecture 18 Global Illumination BRDFs Raytracing and Radiosity Subsurface Scattering Photon Mapping [Ch. 13.4-13.5] March 28, 2012 Jernej Barbic University of Southern California