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- CGI and Compositing
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Television has a more limited color range than your computer. So what you see on your computer will be different than what you see on the TV screen. You will have to know what television format your work will be shown in. It may be shown in:
Resolutions for NTSC and PAL are 640 x 480 and 720 x 540 pixels respectively. Because the display is fairly small, you can get away with smaller file resolutions without noticing too much degradation in your CG. But if the camera is not moving or is not focusing on your object, your resolution will have to increase by a double (1024 x 1024) or quadruple (2048 x 2048) factor. So the resolution of your texture will necessarily be determined by the format of the project you are working on.
Another consideration for TV is illegal color. The color space of television is limited to a certain palette, which is only a fraction of your computer palette. Your computer is able to generate millions of colors, but not all of those colors are reproducible on TV. These un-reproducible colors are called “illegal colors.” These colors are too intense for use in television production due to the limitations of the medium. In the best possible scenario you would use a color scope that is attached to a NTSC color monitor so you will know which colors are too “hot” for TV. Adobe does have a calibration kit that comes with Photoshop so you can mimic the NTSC monitor.
A TV monitor refreshes progressive scan lines, one after another, to generate the TV image on your screen. These scan lines are two interlaced fields.
When you output your textures you will have to watch for thin lines in your textures and also for intricate patterns. Because of the way the television display uses scan lines, if you have thin lines or intricate patterns in your texture, they will vibrate on the screen. I am sure you have all seen this when a news anchor chooses the wrong outfit to wear on air, and their jacket or clothing seems to vibrate on the screen. The smaller the display, the smaller you can render your textures, as long as the camera doesn’t come too close to your object.
The considerations for output for HDTV are very much the same as for NTSC and PAL, as far as illegal colors and interlaced fields are concerned. Although you are able to get away with more thin lines or intricate patterns than with either NTSC or PAL, it is a good rule of thumb to avoid them. Because HDTV is more like film, your textures must reflect film-comparable quality, which means higher resolution files.
HDTV has resolutions of 720 x 1080 or 1080 x 1920.
Film does not have the same color limitation problems as TV. Their basic nature is different because TV is an electronic medium while film quality is a function of chemical processes. The color space of film does have its limitations, nonetheless. Some of the details that you can see on your computer will not show up on film. This is particularly the case with pure blacks and with pure whites. So when you output for film, if you are not careful, your details in pure blacks tend to fall off. The effect is a blob of black where you are thinking there will be detail. With the pure whites, where there are no details, just a wash of white appears.
Your textures for film have to be flawless. You can cheat a little if your CG has a lot of camera movement. But if your CG is the main focus in the scene, you have to make sure your resolution holds up.
Typical resolutions for film:
* 914 x 666 or 1K, which is then enlarged 200% when printed to film.
* 1828 x 1132, or 2K not enlarged. If this small size does get enlarged, it generates a softer CG.
Planning Considerations for Video/Computer Games
King Kong game
When it comes to working on images for video/computer games, once again, it is key to know what format you will be working in. Type of games include:
* “Pre-rendered” games, which involve more detail and are slower paced.
* “On the fly” games, which are rendered as you go. These use polygonal models with maps at a minimum-size resolution. These games have simplified details which increase ease of movement and permit them to be faster paced.
Each will have a different resolution output for your textures. The determining factors in games are:
* Amount of detail
* Developer’s choice of engine
* Less than full-screen imagery
* 8-bit color palette
* Polygonal geometry or NURBS
Basic rules for games:
* Keep texture maps as small as the medium allows.
* When you are building textures with large bitmaps for games, they are 1024 square. 1024 x 1,361 = 1,394,606.
* Use repeated textures when you can.
* Tileable textures load faster and take less processing power.
Also, when you are creating textures for games, unlike for other mediums, you can paint shadows, highlights, and basic lighting effects on your textures. This is due the lack of real-time lighting in the game engine.
The Texture Map
Using 3D software, you can create objects with the use of geometry to establish a shape. To recreate a surface with varying characteristics you can utilize a texture map. Texture mapping was invented by Edwin Catmull, who is a computer scientist and the president of the animation studio Pixar.
Texture mapping is a process of adding surface detail to a CG graphic or a 3D model. When manipulating an image as a texture map, you can think of it as wrapping an object with a texture, much like a package can be wrapped with paper.
Textures can be created with 3D software or other software. What you will be creating in this class are bitmap images or file textures separate from the 3D world, using software like Photoshop or Painter, as well as through painting by hand.
Note: Maps will be covered in greater detail in Module 6.
Once you have determined the medium that you will be working in, you need to consider some of the other attributes that are important to your textures.
As defined in Session 1, a texture map is a bitmap or raster-based image that is measured in pixels. Let’s first consider the definition of bit-depth: it is a way of specifying color resolution in an image by measuring the number of bits devoted to each component of the pixels in the image.
Bit-depths for textures can include the following:
* 8bits per channel, which yield 256 color values
* 16bits per channel, which yield 65,536 color values
When you are saving the textures you create, you will want to consider the bit depth of your images. Remember that bit depths may change as a function of the file format in which you choose to save your texture.
Each file format has different advantages and disadvantages in the way it deals with color depth or bit depth information. The file format that you choose will also be determined by the medium to which you are outputting.
Here are the basic file formats that you can use to save your texture. Be aware of their advantages and disadvantages to find the best format for your project.
File formats include the following:
* 2 bit to 8 bit formats, which yield 256 discrete colors. The discrete color value represents a color interval that shifts a uniform amount to the higher end of the spectrum from its neighbor, and is the same width as its neighbor.
* Non-compressible by programmer.
* Indexed 2 bit to 8 bit, yielding up to 256 discrete colors. Indexation is a method of storing image data in which the value of the pixel refers to an entry in the table of available colors rather than a numerical specification of the color itself.
* Non-compressible by programmer.
* Three channels of 8 bit values, which equals 32 bits.
* 24 bit, or RGB color, plus 8 bit Alpha equals four channels of 8 bit values.
* Compressible by programmer.
* Discrete color.
* 32 bit, or CMYK color, which equals four channels of 8 bit values.
* 40 bit or CYMK-Alpha color.
* Compressible by programmer.
To produce your output, you will create maps that are best for the project you are working on in terms of size and resolution. You always want to use the lowest pixel resolution possible — without loosing quality — to lower your render times. A good general rule is to create images with equal sides, using binary multiples of 2, as in the following sequence: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024.
The reason for using a square format is that only one mathematical calculation is necessary for determining scaling of height and width while rendering. Hence your render times will be shorter.
You can also create a single color field using one repeated pixel.