Computer Graphics

Two File Types: Vector & Raster

Example: Line

end Vector direction start

Vector length angle midpoint etc…

Vectors: Creates easily defined and manipulated objects, like lines, curves, boxes, cylinders, etc… Vector data can be in 2D or 3D. Vector files are relatively small in size.

Problem: Not all information is based on objects. (i.e. photographs and paintings) No real practical way to experience vector data. (i.e. monitors and printers use a grid of dots or pixels.)

Raster

Pixel

Raster: Best when used to represent pictures or images. Raster data is very portable with common, device independent formats (i.e. computer, camera, etc…). Pixels are easily viewed on a monitor or printed on paper.

Problem: Not all information is based on images. (i.e. lines, curves, boxes, cylinders, etc…) Difficult to modify. Limited to 2D. File sizes can be very large. Aliasing is a problem

Problem: aliasing

Solution 1. anti-aliasing

Solution 2. Use a lot of “small” pixels

Raster (pixels) vs Vectors (geometry)

OK, So let’s make a wall

Pixels?

or Geometry?

How about a brick wall?

Geometry?

or Pixels?

Geometry: Pros: Fully three-dimensional Casts shadows, reflections, etc… Easier to position and modify Cons: Takes more time to calculate (render) - Slow Complex textures hard to model

Pixels: Pros: Takes less time to calculate (render) – Fast Easily represents complex textures Cons: Can be difficult to accurately position Modification requires different software Usually requires external files (texture maps)

Example: Still Image Usually scrutinized – More detail is required.

Example: Still Image Large images need lots of Pixels, resulting in long calculations, or render times (above image over 1 hour for 3000x2000 pixels).

Example: Animation Individual frames less scrutinized – need less detail.

Example: Animation Smaller images require fewer pixels, thus shorter rendering times per frame (above image 10 minutes per frame). BUT,….

Example: Animation Long animations require many frames (above animation has 2000 frames).

Example: Animation At 10 minutes a frame, entire animation requires 20,000 minutes to complete (about 14 machine days).

Example: Video Games Action and interactivity demands immediate or real-time rendering (times).

Example: Video Games To lower rendering times, game designers use “low polygon modeling” and extensive texture mapping. Simple geometry + pixels = fast rendering times.