Evolution of Imaging Technology in Computer Graphics. Related Areas

Transcription

1 Evolution of Imaging Technology in Computer Graphics Jonas Gomes Rio de Janeiro Image computation Related Areas 1

2 Related Areas An integrated view Problems on the frontiers Graphical Objects Shape Attributes Graphical Object Geometric Modeling Geometric Model Complex Geometry Complex Topology Attributes (Color, Material, etc.) 2

3 Graphical Object Image Processing Image Simple geometry Simple topology Complex attributes (Color variations) Inverse problem Image analysis Graphical Objects: Image Geometric models Computer Vision 3

4 Image Synthesis Direct problem Known as Computer Graphics Graphical Objects: Image Geometric models Image Synthesis Light, Camera, Simulation! Construct the scene Modeling the Geometry Illuminate the scene Model the light sources Photograph the scene Shading computation Visualization 4

5 What is Computer Graphics? Image computation as a whole geometric modeling image synthesis image analysis image processing Current definition on the literature Computer graphics transforms data into images Better definition Description, Synthesis, Analysis and Processing of Graphical Objects Modeling + Shading Mathematical models Geometric models Illumination models Discretization Representation Numerical computation Discretization Implementation Implementation Algorithms 5

6 The Wireframe Era Geometric Model No geometric structure No solids or surfaces Visualization No shading (Wireframe) Visualization Visualization Main Problems Visualization Hidden line algorithms Modeling Robust Geometry Lines x Surfaces (Hidden surfaces) Mathematical theory of modeling Modeling Technological and Conceptual Constraints Vector and raster graphics 6

7 Shading models Diffuse shading (Lambert s law) Local shading Only light sources illuminate the objects Global shading Interaction of light and scene objects Global shading Shading models Ambient light (empirical) Diffuse only Diffuse + Ambient 7

8 Shading Models Shading computation Flat Shading (Bouknight, 1970) Interpolating Intensities Gouraud shading (1971) Material Properties Shading Models Ambient + Diffuse + Specular Phong model of highlights (1975) 8

9 Shading Models Shading computation Flat Shading (Bouknight, 1970) Intensity interpolation (Gouraud, 1971) Phong Shading (1975) Normal interpolation Shading Models From wireframe to Phong 9

10 Main Problems Blinn-Newell (1977) Problem 3: Refraction has not been satisfactorily simulated Problem 4: All existing models use point light sources Global Shading Light sources Modeling Shading Models An important problem Material properties Better interaction of light and material Cook-Torrance (82) 10

11 Texture Mapping Change of paradigm (Catmull, 1974) Image based shading Modeling the micro geometry Sampled and Reconstructed Material Is this computer graphics? The complete sequence 11

12 A Plethora of Maps Reflectance Mapping (Blinn, Newell, 76) Simulating reflections Bump mapping (Blinn, 78) Simulate rugosities Global Illumination Ray tracing (Turner Whitted, 1980) Geometric optics Specular reflection and transmission 12

13 The Specular Era Ray Tracing Global Illumination Another solution for Diffuse Shading Radiosity (Cornell, 1984) Heat propagation model 13

14 Radiosity Simplified Illumination Equation Diffuse environments Main Problems Computational complexity Incorporate specularity on radiosity Need for a Unified model specular diffuse 14

15 Main Problems Blinn-Newell (1977) Problem 6: The various individual techniques must be combined in a consistent way The Rendering Equation (Kajyia, 1986) Unification of the illumination problem The Rendering Equation One Equation Different approximations Different computing strategies Conceptual unity Local models (Utah approximation) Ray tracing (Monte Carlo) Radiosity (Finite elements) Path tracing (Backwards raytracing) Hybrid methods 15

16 A hybrid technique Path Tracing Finally Caustics! 16

17 Problems Blinn-Newell (1977) Problem 1: There is a great disparity between the complexity of scenes in the real world and synthetic scenes Problem 2: Many objects in nature are not well described as smooth surfaces with small perturbations. Hair and clouds are out of reach of current techniques A Great Challenge 17

18 Complexity of the Geometry Fractals Is there a geometry at all? The Fractal Geometry of Nature How to model fractals? How to render fractals? The noise function Ken Perlin State of the art in plant modeling 18

19 Live action or synthetic? Scene from 101 Dalmatians by Walt Disney What is the goal? Generate Photorealistic images Applications Applications Special Effects Virtual Worlds Movie industry Television industry Theme parks Arcade games 19

20 A Quest for Non-photorealism The need for non-photorealistic images Illustration Pen and ink painting Architectural rendering The Printing industry Technical illustration Non-photorealistic 20

21 Pen and ink illustration Non-photorealistic Painting effects Non-photorealistic Watercolor Impressionism 21

22 A Great Challenge Today Generate real time, low-cost photo-realistic images Many applications Data Mining Seismic data Geographical Information Systems Medical Images Architecture Arcade games An important issue Interactivity Efficiency Major problems Large data bases Current Trends Limited computational power An interesting problem Scene navigation 22

23 In Search for a Solution Change the paradigm of image generation Traditional paradigm: The plenoptic function 23

24 Plenoptic function Rendering and the plenoptic function A New Paradigm Visualize samples of the plenoptic function 24

25 New Paradigm? Image Based Rendering Revisit the seventies New technology Faster computers Integrating the three areas of image computation A tour into the picture (Video) A simple example Virtual Panoramas Camera in fixed position Panoramic Surface Viewing Projection 25

26 An Example Navigation using panoramas Software No immersibility Visorama Project IMPA (Visgraf Lab) Escola de Comunicação da UFRJ visorama/ 26

27 Binocular device Stereo Sound Immersive Image Based rendering Degrees of freedom Fixed viewpoint Pan and tilt rotation Zoom Visorama Visorama Device Rotating Head Tilt Sensor Pan Sensor 27

28 Rotating Head Event Button Zoom Buttons Binocular Display Processing Panoramic Images Tiling Rendering Region of Intersection Visualization Window 28

29 Visualization of Urban Landmarks Tourism Visualization of urban landmarks The virtual time machine Education Demonstrations Video The Visorama Project 29

30 Raytracing Software: Rayshade www-graphics.stanford.edu/~cek/rayshade/rayshade.html Public Domain Well documented Windows, UNIX PoVRay Public domain (Unix / Windows) Raytracing and Radiosity 30

31 Radiance Software Raytracing with Diffuse reflection Ward, Rubinstein and Clear, 1988 Radiance Software Lighting design (Physically based shading) Well documented and books 31