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documentation:development:opera:pf25:ppgfldr:ggsfldr:gpgfldr:1gpga [2022/10/10 16:53] – created - external edit 127.0.0.1documentation:development:opera:pf25:ppgfldr:ggsfldr:gpgfldr:1gpga [2023/03/16 22:35] (current) – trapexit
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 ====== NTSC Display Basics ====== ====== NTSC Display Basics ======
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 The final graphics product of the 3DO system is a signal sent to an NTSC television display. Because all of the graphics hardware within the 3DO system is aimed at this goal, the NTSC standard is the first place to start for understanding 3DO graphics. This chapter won't try to discuss all of the workings of an NTSC display-that's a topic for a book devoted to NTSC. You'll find just enough information here to understand how the 3DO graphics components time their operations and format the image they send to the display. The final graphics product of the 3DO system is a signal sent to an NTSC television display. Because all of the graphics hardware within the 3DO system is aimed at this goal, the NTSC standard is the first place to start for understanding 3DO graphics. This chapter won't try to discuss all of the workings of an NTSC display-that's a topic for a book devoted to NTSC. You'll find just enough information here to understand how the 3DO graphics components time their operations and format the image they send to the display.
  
-If you're an NTSC pro and already know the basics, you can skip the first part of this section and turn to [[:documentation:development:opera:pf25:ppgfldr:ggsfldr:gpgfldr:#xref31570|3DO NTSC Graphics]].+If you're an NTSC pro and already know the basics, you can skip the first part of this section and turn to [[.:1gpga#do_ntsc_graphics|3DO NTSC Graphics]].
  
 ===== Image Scanning ===== ===== Image Scanning =====
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 To get rid of the flicker, NTSC divides each set of frame scan lines in half; each half-frame is called a //field.// The first field, called the odd field, contains all the odd-numbered scan lines (which are numbered starting from the top of the screen). The second field, called the even field, contains all the even-numbered scan lines. The two fields are interlaced as shown in Figure 1 to create a full frame. To get rid of the flicker, NTSC divides each set of frame scan lines in half; each half-frame is called a //field.// The first field, called the odd field, contains all the odd-numbered scan lines (which are numbered starting from the top of the screen). The second field, called the even field, contains all the even-numbered scan lines. The two fields are interlaced as shown in Figure 1 to create a full frame.
  
-{{:documentation:development:opera:pf25:ppgfldr:ggsfldr:gpgfldr:figures:g.01-1.png|Graphic cannot be displayed}}+{{.:figures:g.01-1.png|Graphic cannot be displayed}}
  
 **Figure 1:** //NTSC fields.// **Figure 1:** //NTSC fields.//
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 When an NTSC's electron beams scan the phosphors of the display tube, they follow a set scan pattern shown in Figure 2. They scan the first line of a field, moving left to right, as they change intensity to change color and intensity on the screen. At the end of the first line, they turn off, their aim moves left to start at the beginning of the next line, then they turn on again and scan another line. The interval between the end of one scan line and the beginning of the next is called the //horizontal blank,// a period when nothing is beamed onto the display screen. When an NTSC's electron beams scan the phosphors of the display tube, they follow a set scan pattern shown in Figure 2. They scan the first line of a field, moving left to right, as they change intensity to change color and intensity on the screen. At the end of the first line, they turn off, their aim moves left to start at the beginning of the next line, then they turn on again and scan another line. The interval between the end of one scan line and the beginning of the next is called the //horizontal blank,// a period when nothing is beamed onto the display screen.
  
-{{:documentation:development:opera:pf25:ppgfldr:ggsfldr:gpgfldr:figures:g.01-2.png|Graphic cannot be displayed}}+{{.:figures:g.01-2.png|Graphic cannot be displayed}}
  
 **Figure 2:** //NTSC scan pattern.// **Figure 2:** //NTSC scan pattern.//
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 Notice that scan lines aren't perfectly horizontal in Figure 2, but slightly slanted down as they move left. Notice too that the 525 frame lines are divided exactly in half, so each field gets 262.5 scan lines-hence the half-line in each frame in the figure. Although the figure shows the true physical nature of NTSC scan lines, for all practical purposes you can consider each scan line as perfectly horizontal and disregard half-lines; they're invisible in each frame and aren't used for drawing. Think of each field created by 3DO hardware as a set of 240 perfectly horizontal and full scan lines. Notice that scan lines aren't perfectly horizontal in Figure 2, but slightly slanted down as they move left. Notice too that the 525 frame lines are divided exactly in half, so each field gets 262.5 scan lines-hence the half-line in each frame in the figure. Although the figure shows the true physical nature of NTSC scan lines, for all practical purposes you can consider each scan line as perfectly horizontal and disregard half-lines; they're invisible in each frame and aren't used for drawing. Think of each field created by 3DO hardware as a set of 240 perfectly horizontal and full scan lines.
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 ===== 3DO NTSC Graphics ===== ===== 3DO NTSC Graphics =====
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 Much of the 3DO hardware's processing time is spent preparing an image for NTSC presentation; it's crucial that graphics processes are timed to coincide with the presentation rate of frames, fields within the frames, and scan lines within the fields. To make that possible, the 3DO hardware provides signals at the beginning of each horizontal and vertical blank. Some processes, such as those that change available colors for an image, use horizontal blank signals so they can work to change conditions between one scan line and the next. Other processes, such as those that refresh background images, use vertical blank signals to work between fields or between frames. Much of the 3DO hardware's processing time is spent preparing an image for NTSC presentation; it's crucial that graphics processes are timed to coincide with the presentation rate of frames, fields within the frames, and scan lines within the fields. To make that possible, the 3DO hardware provides signals at the beginning of each horizontal and vertical blank. Some processes, such as those that change available colors for an image, use horizontal blank signals so they can work to change conditions between one scan line and the next. Other processes, such as those that refresh background images, use vertical blank signals to work between fields or between frames.
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 +Original: https://ext.3dodev.com/3DO/Portfolio_2.5/OnLineDoc/DevDocs/ppgfldr/ggsfldr/gpgfldr/1gpga.html
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documentation/development/opera/pf25/ppgfldr/ggsfldr/gpgfldr/1gpga.1665435215.txt.gz · Last modified: 2022/10/10 16:53 by 127.0.0.1

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