Βασικοι οροι 3D gaming κουβεντας και mini FAQ

[Wally]

Ειδα ενα πολυ ενδιαφερον ποστ στο Beyond3D και σας το παραθετω αυτουσιο διοτι αξιζει.

Ισως λυσει καποιες αποριες ή αποσαφηνισει καποια θεματα πανω στα βασικα τεχνικα της 3D gaming κουβεντας...

How-To and other useful explanations:

How to tell the resolution of a backbuffer based on the outputted image:

Someone has yet to take the time to compile all the relative information in a single comprehensive post. So bear with us and track down some of that information in the following posts:

http://forum.beyond3d.com/showpost.php?p=1070774&postcount=273

http://forum.beyond3d.com/showpost.php?p=1070972&postcount=282

http://forum.beyond3d.com/showpost.php?p=1071006&postcount=284

http://forum.beyond3d.com/showpost.php?p=1071084&postcount=292

http://forum.beyond3d.com/showpost.php?p=1065791&postcount=225

http://forum.beyond3d.com/showpost.php?p=1065280&postcount=222

http://forum.beyond3d.com/showpost.php?p=1167507&postcount=29

Frame Buffer Calculations & Memory Consumption

Back-Buffer(s) = Pixels * FSAA Depth * Rendering Colour Depth (may include multiple render targets for deferred rendering techniques)

Z-Buffer = Pixels * FSAA Depth * Z Depth (usually 32-bit depth)

Front-Buffer(s) = Pixels * Output Colour Depth (this is what you see, almost always resolved to 8-bit per component rather than 10-bit or 16-bit)

Total = Back-Buffer(s) + Z-Buffer + Front-Buffer(s)

Note: For Xenos, the back buffer and z-buffer must fit within the 10 MiB (10*1024*1024 bits, 8 bits/byte) to avoid tiling.

Frame buffer formats

RGBA8 = 8 bits for Red, 8 bits for Green, 8 bits for Blue, 8 bits for alpha = 32 bits per pixel

FP10 = 10 bits for RGB components, and 2 bits for alpha = 32 bits per pixel

FP16 = 16 bits for each component = 64 bits per pixel (no support for hardware alpha blending on Xenos)

NAO32 = LogLUV conversion, In-Depth explanation = 32 bits per pixel (no hardware alpha blending)

Example: 1120x585, 2xMSAA, FP10, 32-bit Z-buffer

back buffer + Z = 1120*585*2*(32/8 + 32/8 ) = 10483200 bytes = 9.9975... MiB

Aspect Ratio

Some of you might be wondering how games like Call of Duty 4 (1.71:1) , Halo 3(1.8:1) , Metal Gear Solid 4 (4:3) can have rendering resolutions that are not 16:9 aspect ratio. All you need to learn about is anamorphic widescreen. The image is squeezed into the rendered resolution but is then stretched to the proper 16:9 presentation.

An example of this squeezing can easily be seen in any Doom 3 engine games (Quake 4/Prey/Quake Wars). If you have one of them handy on your PC (latest version will do), try setting your resolution to 960x720 and in the console type r_aspectratio 1 for 16:9 or 2 for 16:10. All you'll see is the in-game view being squeezed/stretched horizontally. On the flip side, if you render the game at 1280x720 while still in 4:3 mode, the Mancubus just might be the fattest enemy you'll ever see. You can help it lose some weight by setting the game to 16:9. And of course, the isomorphic 1280x720 rendition will offer more image clarity than the anamorphic 960x720.

Multisample AA

Multiple geometry/sub-sample (reddish squares in below images) points with a particular weighting (surrounding the texture sample point, green square in below images) are used to determine the colour of the pixel being rendered. Sample positions can differ between AMD/nVidia. As RSX is based on the G70 architecture, the following sample patterns should apply. In the case of Xenos, it would not be unreasonable to assume that it uses the same patterns as ATI has used in the past (R300+).

The result for 2xMSAA is that there may be one intermediary shade in between polygon edge steps; one sample is found to be within one polygon (e.g. colour A), and the second sample is found in another polygon (e.g. colour B). If both sample points have equal weightings, the resultant pixel would be 50% colour A, 50% colour B. Obvious results are obtained when a polygon edge bisects the shortest imaginary line connecting the two geometry sample points. Hence, 2xMSAA for G70 will look slightly different to 2xMSAA for R520 (see sample positions below).

For the case of 4xMSAA, there may be more shades in between polygon edge steps due to the higher number of geometry samples, resulting in a smoother transition between steps. With equal weightings to each sub-sample, there will be three intermediary shades.

The easiest way to see MSAA level is to have a straight-edged object overlapping another object/background with a high contrast in colours between the two e.g. black object against a white background. Beware of JPG compressed screenshots where pixels near high frequency components (edges) can be distorted.

G70 sample patterns

2xMSAA

http://www.beyond3d.com/images/reviews/g70/2x.png

4xMSAA

http://www.beyond3d.com/images/reviews/g70/4x.png

R520 - sample patterns

2xMSAA

http://www.beyond3d.com/images/revie...aa_samp_2x.gif

4xMSAA

http://www.beyond3d.com/images/revie...aa_samp_4x.gif

Quincunx AA on PS3 - two geometry sample points are used just like 2xMSAA (so the same storage cost), but it also uses 3 samples belonging to neighbouring pixels (regardless of a polygon edge) to the right and below of the original texture sampled point (see sample pattern image for clarity). The result is a blurring of the entire image, but higher perceived polygon AA. Consider a texture of higher frequency components, lots of different colour patterns. The current pixel's two geometry sample points indicate the pixel is entirely within one polygon. However, the three neighbouring sub-samples are still accounted for in the final pixel, hence the overall image blur.

Quincunx sample pattern

http://www.beyond3d.com/images/revie...plepattern.jpg

Comparison between 2xMSAA/QAA/ & blur filters

http://upsilandre.free.fr/images/Quincunx.jpg

Temporal AA on PS3 (ala Quaz)- odd and even frames are rendered with a half-pixel shift. The current frame is blended with the previous frame to achieve a similar effect as super sample AA for static scenes. In a moving scene, the blending of the odd and even frames produces a persistent blurring of the image. However, this is also advantageous for the edges of alpha-to-coverage primitives, because traditional multisampling does not work*, only super sampling.

*see transparency AA or adaptive AA settings on appropriate PC hardware.

Black Levels & Output

Xbox 360

Standard = 16-235

Intermediate

Expanded = 0-255

PS3

Limited Range = 16-235

Full Range = 0-255

Wii

Undocumented at the moment (feel free to address the issue)

Current list of game rendering resolutions and IQ

• List for Playstation 3 Games
  
• List for Xbox 360 Games
  

Archive of the older threads on the same topic:

Thread 1: The Neverending Upscale Discussion Thread * Summary=#457




http://forum.beyond3d.com/showthread.php?t=43330

Thread 2: Neverending Upscaling/Resolutions/AA etc Thread #2 *Rules: post: #616 *

http://forum.beyond3d.com/showthread.php?t=46242

Thread 3: Neverending Upscaling/Resolutions/AA etc Thread #3 (Rules Post #1!)

http://forum.beyond3d.com/showthread.php?t=48252

Footnotes

Thanks to all the people who contributed to the list, took captures and wrote large parts of the explanations. AlStrong, Quaz51/Upsilandre, grandmaster, dot50cal, etc.