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01.1 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics: 1980-1990 Realism comes to computer graphics smooth shadingenvironment.

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Presentation on theme: "01.1 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics: 1980-1990 Realism comes to computer graphics smooth shadingenvironment."— Presentation transcript:

1 01.1 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics: Realism comes to computer graphics smooth shadingenvironment mapping bump mapping

2 01.2 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics:  Special purpose hardware  Silicon Graphics geometry engine VLSI implementation of graphics pipeline  Industry-based standards  PHIGS  RenderMan  Networked graphics: X Window System  Human-Computer Interface (HCI)

3 01.3 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics:  OpenGL API  Completely computer-generated feature- length movies (Toy Story) are successful  New hardware capabilities  Texture mapping  Blending  Accumulation, stencil buffers

4 01.4 Angel: Interactive Computer Graphics Addison-Wesley 2005 Computer Graphics:  Photorealism  Graphics cards for PCs dominate market  Nvidia, ATI, 3DLabs  Game boxes and game players determine direction of market  Computer graphics routine in movie industry: Maya, Lightwave  Programmable pipelines

5 01.5 Angel: Interactive Computer Graphics Addison-Wesley 2005 Image Formation

6 01.6 Angel: Interactive Computer Graphics Addison-Wesley 2005 Objectives  Fundamental imaging notions  Physical basis for image formation  Light  Color  Perception  Synthetic camera model  Other models

7 01.7 Angel: Interactive Computer Graphics Addison-Wesley 2005 Image Formation  In computer graphics, we form images which are generally two dimensional using a process analogous to how images are formed by physical imaging systems  Cameras  Microscopes  Telescopes  Human visual system

8 01.8 Angel: Interactive Computer Graphics Addison-Wesley 2005 Elements of Image Formation  Objects  Viewer  Light source(s)  Attributes that govern how light interacts with the materials in the scene  Note the independence of the objects, the viewer, and the light source(s)

9 01.9 Angel: Interactive Computer Graphics Addison-Wesley 2005 Light  Light (cahaya)  bagian dari spektrum elektromagnet yang dapat bereaksi terhadap sistem visual kita  wavelengths pada rentang nm (nanometers)  Long wavelengths merah dan short wavelengths sebagai biru

10 01.10 Angel: Interactive Computer Graphics Addison-Wesley 2005 Ray Tracing and Geometric Optics Salah satu cara pembentukan image, dengan mengikuti sinar cahaya dari titik sumber hingga titik masuknya cahaya pada lensa. meskipun, Tiap sinar cahaya memungkinkan mengalami beragam interaksi misalkan hingga terabsorbsinya oleh objek ataupun menuju titik infinity.

11 01.11 Angel: Interactive Computer Graphics Addison-Wesley 2005 Luminance and Color Images  Luminance Image  Monochromatic  Values are gray levels  Analogous to working with black and white film or television  Color Image  Has perceptional attributes of hue, saturation, and lightness  Do we have to match every frequency in visible spectrum? No!

12 01.12 Angel: Interactive Computer Graphics Addison-Wesley 2005 Three-Color Theory  Human visual system has two types of sensors  Rods (batang): monochromatic, night vision  Cones Color sensitive Three types of cones Only three values (the tristimulus values) are sent to the brain  Need only match these three values  Need only three primary colors

13 01.13 Angel: Interactive Computer Graphics Addison-Wesley 2005 Shadow Mask CRT

14 01.14 Angel: Interactive Computer Graphics Addison-Wesley 2005 Additive and Subtractive Color  Additive color  Form a color by adding amounts of three primaries CRTs, projection systems, positive film  Primaries are Red (R), Green (G), Blue (B)  Subtractive color  Form a color by filtering white light with cyan (C), Magenta (M), and Yellow (Y) filters Light-material interactions Printing Negative film

15 01.15 Angel: Interactive Computer Graphics Addison-Wesley 2005 Pinhole Camera x p = -x/z/dy p = -y/z/d Use trigonometry to find projection of point at (x,y,z) These are equations of simple perspective z p = -d

16 01.16 Angel: Interactive Computer Graphics Addison-Wesley 2005 Synthetic Camera Model center of projection image plane projector p projection of p

17 01.17 Angel: Interactive Computer Graphics Addison-Wesley 2005 Advantages  Separation of objects, viewer, light sources  Two-dimensional graphics is a special case of three-dimensional graphics  Leads to simple software API  Specify objects, lights, camera, attributes  Let implementation determine image  Leads to fast hardware implementation

18 01.18 Angel: Interactive Computer Graphics Addison-Wesley 2005 Global vs Local Lighting  Cannot compute color or shade of each object independently  Some objects are blocked from light  Light can reflect from object to object  Some objects might be translucent (cahaya tembus)

19 01.19 Angel: Interactive Computer Graphics Addison-Wesley 2005 Why not ray tracing?  Ray tracing seems more physically based so why don’t we use it to design a graphics system?  Possible and is actually simple for simple objects such as polygons and quadrics with simple point sources  In principle, can produce global lighting effects such as shadows and multiple reflections but ray tracing is slow and not well-suited for interactive applications


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