Let's continue our discussion of game graphics concepts. Now, let's focus on the model layer of the graphic display model. The model layer defines how the graphics are represented internally within the game or software. There are three primary graphics models, bitmap, vector, and 3D. A bitmap image stores the color information about each pixel in the image. Therefore, this is sometimes also referred to as a Pixel Map. So for example, the image shown is a 10 pixel by 10 pixel image or essentially 100 pixels of color information. Where some pixels are white and some pixels are blue. The resulting image, when viewed at a distance, looks roughly like a circle. The color information is made up of a certain number of bits of binary information called color depth. For example, one bit of information per pixel would allow you to define just two different color choices. Where else eight bits of information per pixel, would allow you to have up to 256 colors in the image. Most images we work with today in games are 16-bit, 24-bit, or 32-bit depending on if the image ahs transparency information included, which is called an Alpha channel. Big map graphics are the most direct representation to what you see on display. That is, a bitmap image is often directly rendered to the display, therefore bitmap images are sometimes referred to as raster graphics. Obviously you can scale a bitmap image up but the visual quality will diminish as you adjust, zooming in on the pixels that are available. You are not creating new pixels. To achieve a high frame rate in our games, the pixel dimensions of a bitmap image should usually be made to be a power of two to help take advantage of the efficiencies. This allows in the graphics processing unit or GPU. You don't have to make the image square, but both the width and height should be a power of two, such as 512 pixels wide by 256 pixels high. While non power of two images are possible that may slow down the performance of your game, and typically should only be used for user interface elements. Bitmap images can be used not only for 2D graphical elements such as game sprites, photographs and UI elements, but also for texture maps used within materials on 3D geometry. Vector images work very differently than bitmap images. Vector images are stored internally as geometric information or in essence, mathematical equations. So instead of storing the color information for each pixel in an image of a circle, we represent the circle internally as a coded equation within the software, such as draw a circle with radius 5 and border 1. Of course, we usually are making much more elaborate vector images through the use of geometric primitives, curves and gradient coloring. Using vector graphic tools, artists can easily achieve a fun cartoon book without having to know any math. Vector images have the advantage over bitmap images in that you can scale them up without the image becoming pixelated. That is vector's scale without losing image quality. However, vectors have the disadvantage of taking longer to render than bitmap images. When the vector is displayed, it is first converted into the desired size pixel image, and then rendered to the display. This extra step of converting the vector into a pixel map takes computer processing time. While some game engines do support vector images, bitmap images are often used in games when high frame rate is desired. However, vector images still have their place in game development. Vector graphics can give you that cartoon look. Vectors are also often used in UI elements, such as icons and fonts. And let's not overlook 3D graphics. 3D graphics are essentially vector graphics in three dimensions. That is a 3D model is defined by geometric polygons to create the mesh of the model. The more polygons that are used, the more detail that can be displayed. Or stated another way, the more organic or smooth the model will look. When rendering the 3D graphics, the graphics processing unit in the computer hardware often converts the polygon, which may have several vertices into triangles for efficiency purposes. The more polygons, the more triangles, the longer it will take the computer to render the 3D model. Therefore in game development when we want real time rendering of 3D graphics, we often try to limit the number of polygons or tris, or use low-polygon modeling, so the game runs at a high frame rate. The model itself only has geometric data, it will not include colors or other details. This is where we combine modeling with bitmap techniques to give us the best of both worlds. Textures can be more than just color. Normal maps give us control over how light reflects off of a surface. Which will, in turn, give us the ability to create the illusion of surface detail. Modern triple A 3D graphics are a combination of low polygon models with texture maps baked from high polygon models. Combining anywhere from 4 to 12 maps on a single model gives us photorealism in real time graphics. [MUSIC]
