1. Digital Media Dr. Jim Rowan ITEC 2110 Vector Graphics II

2. Manipulating objects AKA closed curves Translation is a simple up/down side-to- side movement Scaling: make bigger or smaller Rotation about a point Reflection about a line

3. Object fills Solid color Patterns Gradients –linear –radial

4. 3-D... 3 dimensions x, y and z x & y form the ground plane z is the height

5. 3-D Way more complex than 2-D 3-D shapes (objects) are defined by their surfaces Made even more complicated by the fact that a 3-D object inside the computer must be translated into 2-D to be rendered on a computer screen... –This results in the need to specify the viewpoint

6. 3-D: additional complexity lighting –natural –artificial atmosphere surface texture rendering is extremely computationally expensive (demanding)

7. Managing Complexity

8. Structural hierarchy Things in the real world are compositions of smaller things Things in the 3-D graphics world are also compositions of smaller things Hierarchical structure is an excellent way of coping with complexity Also seen in object-oriented programming like Java and Squeak!

9. Structural hierarchy Car –Wheels (4) tire wheel hubcap –Doors (2) handles –inside »lever –outside »button »handle window(s) –Lights headlights (2) tail lights (2+) stop lights (2+)

10. 3-D: additional complexity rendering is extremely computationally expensive (demanding) –lighting natural artificial reflections off other objects in the scene shadows cast by other objects in the scene –surface texture affects appearance

11. 3D Models

12. 3-D models Building things from known shapes Constructive solid geometry –uses geometric solids: cube, cylinder, sphere and pyramid –objects build by squishing and stretching those objects –objects joined using union, intersection and difference

13. 3-D models constructive solid geometry Union –new object is made from the space occupied by both objects Intersection –new object is made of the space that the two objects have in common Difference new object is made from one object’s subtraction from another object

14. 3-D models Free Form Building things one side at a time Uses an object’s surface (it’s boundary with the world) to define it Build surfaces from flat polygons or curved patches –flat polygons are easier to render and therefore frequently used in games where computational power is limited Results in an object drawn as a “mesh” Can be done using Bezier surface patch but have 16 control points More tractable patch uses a surface called a non- rational B-spline

15. 3-D models Free Form: Extrusion Building things using a paydoh factory Draw a 2 dimensional shape through space along a line The line can be straight or curved

16. 3-D models Meat balls Reacts like soft objects rather than hard, solid ones Think of it as having surface tension Kinda like an uncooked meatball, press two of them together and they “squish”

17. 3-D models Procedural modeling Best known is based on Fractals –Fractals –exhibit the same structure at all levels of detail –aka “self similar” –used to model natural objects –http://en.wikipedia.org/wiki/Fractal Particle systems... many particles, few controls Physics... distribution of mass, elasticity, optical properties, laws of motion

18. 3-D Rendering Rendering engine handles the complexity Wire frames are used to preview objects and their position –can’t tell which surface is closer to us and which surface is hidden To save computation time, hidden surfaces are removed before rendering –Why render what can’t be seen?

19. 3-D rendering Lighting –Added to scene much like an object –spot light, point source, floodlight... –position and intensity Direct relationship between rendering quality and computational burden

20. 3-D rendering Shading... how light reacts with surface –Based roughly on physics but modified by heuristics (rules derived from experience) –Examples ===> Texture mapping –An image is mathematically wrapped around the object

22. 3-D rendering Light reflecting off objects of one color affect the color and lighting of surrounding objects –Ray tracing Complex... must be repeated for pixel in the image... photo-realistic results –Wayne Wooton Pixar –Radiosity

23. Questions?