Aliasing and Filtering explained - bit-tech.net Forums

WilHarris · 4th Jul 2005, 11:04

http://www.bit-tech.net/hardware/200...ltering/1.html

I'm pretty pleased with how this turned out. It's simple, and possibly a little simplistic, but I think it gets over the ideas behind these techniques without burying you in jargon. Thoughts?

Kameleon · 4th Jul 2005, 11:17

Great job, Wil. Enough detail to understand what's going on without being just too complicated for the mortal man to comprehend (Sorry Tim

) - I'll definitely be showing this to people rather than trying to explain myself

mrplow · 4th Jul 2005, 11:28

Nice, but am I supposed to be able to see something in this shot?

It's a bit on the dark side!

Rys · 4th Jul 2005, 11:47

Pretty good stuff

The basics explained without going too overboard. A good read while I have a tea-break, cheers!

Hamish · 4th Jul 2005, 12:17

Quote:

Originally Posted by mrplow

Nice, but am I supposed to be able to see something in this shot?

[ img]http://www.bit-tech.net/content_images/aliasing_filtering/hl2noaf.jpg[/ img]

It's a bit on the dark side!

lol thats what i was thinking, what bricks?

also those comparison screenies would probably work better if they were a bit bigger, had to zoom in to see the jaggies and nojaggies properly

Shadow_101 · 4th Jul 2005, 12:22

Excellent Read, it’s certainly helped me understand AA an AF better.

Thought the comparison screenshots where fine though, perhaps you guys need to tweak your monitor settings

yodasarmpit · 4th Jul 2005, 12:26

Very good read, one of the best articles yet.
Explained everything in a way I could understand.

Krikkit · 4th Jul 2005, 13:08

Very good article, i don't agree about the pictures though - the bricks example worked really well for me!

Hamish · 4th Jul 2005, 13:25

oh ok, i can see the bricks on this monitor, secondary monitor is set too dark

DigitalX · 4th Jul 2005, 13:50

Hmmp.. JPG? Horrible quality... why dont you use png or gif.. much smaller and better quality with pic that have only a few colors in it.

Good job.

ralph.pickering · 4th Jul 2005, 15:40

Quote:

Originally Posted by mrplow

Nice, but am I supposed to be able to see something in this shot?

It's a bit on the dark side!

I thought the same, but after I tweaked the gamma and contrast in my display settings I could see it OK.

Good article, BTW...

RotoSequence · 4th Jul 2005, 15:59

I think most of us can agree that a brighter spot would have made a better example in the dark photo. But, either way, excellent article - you've made AA and AF easy to understand

RTT · 4th Jul 2005, 16:32

Fantastic article

Tim S · 4th Jul 2005, 17:03

Quote:

Originally Posted by RotoSequence

I think most of us can agree that a brighter spot would have made a better example in the dark photo. But, either way, excellent article timmers - you've made AA and AF easy to understand

I didn't write it, but I had an input.

RotoSequence · 4th Jul 2005, 17:48

Quote:

Originally Posted by bigz

I didn't write it, but I had an input.

Oops

Bindibadgi · 4th Jul 2005, 18:31

Quote:

Originally Posted by RTT

Fantastic article

Indeed! /buttkiss

cpemma · 4th Jul 2005, 19:31

Quote:

Originally Posted by mrplow

Nice, but am I supposed to be able to see something in this shot?

Well, it shows my monitor's set up right, unlike some.

Perhaps links to some freeware aids should be added to the article?

I understood all that and my head doesn't hurt too much,

Stephen Brooks · 4th Jul 2005, 21:32

I'm pretty sure rotated grid 4xAA is _not_ rotated by 45 degrees... I think something more like 26.565 degrees would work better as then the four points have X and Y-ordinates regularly spaced along each axis, so for near-vertical and horizontal lines (where aliasing is arguably worst) it is of the best quality you can do.

OTOH NVidia and ATI might have decided to use 45 degrees for some perverse reason I am too stupid to comprehend... Or maybe I should patent the angle "26.565 degrees" and sell it to them

[edit] Found an in depth article on this http://www.3dcenter.org/artikel/mult...g/index6_e.php with some pictures:

drb · 5th Jul 2005, 08:52

An example of a difference between ATI and Nvidia is the fact that ATI implement gamma-corrected AA on all their 9700+ cards, a technique which samples alpha particles inside triangles as well as gamma particles on the outside of triangles. This is only implemented by Nvidia on the 7800 GTX.

Gamma particles? Is this some sort of inside joke?

I think you have perhaps simplified too much ...

Multisampling does not require samples to be shared between pixels. Its an approach some vendors use to try to get better image quality.

It's misleading to say mipmaps are lower-quality distance textures. They are multi-resolution texture image sets (pyramids) used to approximately match the variable resolutions needed for different object scalings by choosing the closest matching (or pair of matching) images. You probably meant that, but it's not what the article is saying ...

Zidane · 5th Jul 2005, 10:53

very nice article. explains without confusing. gives enough information to inform, without being too technical, and gives the reader many avenues to explore if they want to know more.

4th Jul 2005, 11:04	#1
WilHarris Just another nobody Join Date: Jun 2001 Location: Oxford Posts: 2,671	Aliasing and Filtering explained http://www.bit-tech.net/hardware/200...ltering/1.html I'm pretty pleased with how this turned out. It's simple, and possibly a little simplistic, but I think it gets over the ideas behind these techniques without burying you in jargon. Thoughts?

4th Jul 2005, 11:17	#2
Kameleon is watching you... Join Date: Apr 2003 Location: UK Posts: 3,502	Great job, Wil. Enough detail to understand what's going on without being just too complicated for the mortal man to comprehend (Sorry Tim ) - I'll definitely be showing this to people rather than trying to explain myself __________________ "Can anyone tell me the best way to find out what the ludicrously named 'System Idle Process' is actually doing? I can guarantee it's going to take up 95% of processor resources, just when I'm in the middle of something important." Water/144@2.9/Neo2/GSkill/6800 <@Cainer> eat my pwn, nerds!

4th Jul 2005, 11:28	#3
mrplow obey the fist!! Join Date: Sep 2001 Location: London Posts: 2,428	Nice, but am I supposed to be able to see something in this shot? It's a bit on the dark side! __________________ Big, half-finished, parts hanging out computer ATCS 210; MSI mATX; AMD 4000+; HD4770; 3GB DDR400; 2x120GB + 2x1TB; 19" HANNS-G

4th Jul 2005, 12:22	#6
Shadow_101 Mudkips. Join Date: Feb 2004 Location: Harborne, Birmingham Posts: 1,090	Excellent Read, it’s certainly helped me understand AA an AF better. Thought the comparison screenshots where fine though, perhaps you guys need to tweak your monitor settings __________________ Network Engineering & Security, CCNA, ITIL (F). GM IT Security Analyst

4th Jul 2005, 12:26	#7
yodasarmpit The other Brett. Moderator Join Date: May 2002 Location: West Lothian , Scotland Posts: 9,667	Very good read, one of the best articles yet. Explained everything in a way I could understand. __________________ The Rt. Hon. Alexander Boris de Pfeffel Johnson - "Ping Pong is coming home" www.yodasarmpit.com clickr my flickr

4th Jul 2005, 11:47	#4
Rys What's a Dremel? Join Date: Sep 2004 Location: Sheffield, UK Posts: 6	Pretty good stuff The basics explained without going too overboard. A good read while I have a tea-break, cheers!

4th Jul 2005, 13:08	#8
Krikkit Don't panic! Join Date: Jan 2003 Location: Lancs, UK Posts: 15,216	Very good article, i don't agree about the pictures though - the bricks example worked really well for me! __________________ \|E8400 @ 4.4GHz\|WC: 2*120.1 GT's, MCP350, Storm G5\|4GB Dominators\|DFI LT X48-T2R\|8800GT\|74GB Raptor\|Chieftec BA01\|OCZ ModXStream 600W\|Dell 2208WFP\| The Good, The Bad, The Ugly, The LOL!!1!!1!, The Zlad!, The Kempness, The Braaaaaains...

4th Jul 2005, 13:25	#9
Hamish I Mod, Therefore I Own Join Date: Nov 2002 Location: London Posts: 3,587	oh ok, i can see the bricks on this monitor, secondary monitor is set too dark

4th Jul 2005, 13:50	#10
DigitalX What's a Dremel? Join Date: May 2004 Location: Finland Posts: 17	Hmmp.. JPG? Horrible quality... why dont you use png or gif.. much smaller and better quality with pic that have only a few colors in it. Good job. __________________

4th Jul 2005, 15:59	#12
RotoSequence Lazy Lurker Join Date: Jan 2004 Location: 'States Posts: 4,534	I think most of us can agree that a brighter spot would have made a better example in the dark photo. But, either way, excellent article - you've made AA and AF easy to understand __________________ Technology Schmecnology Last edited by RotoSequence; 4th Jul 2005 at 17:49.

4th Jul 2005, 16:32	#13
RTT bwarp Moderator Join Date: Mar 2001 Location: Berkshire Posts: 12,987	Fantastic article __________________ This post is non-negotiable. All terms and conditions apply. Arguing on the internet is like competing in the special Olympics. Even if you win you're still a retard.

4th Jul 2005, 21:32	#18
Stephen Brooks Minimodder Join Date: Apr 2005 Location: INTERNET Posts: 32	I'm pretty sure rotated grid 4xAA is _not_ rotated by 45 degrees... I think something more like 26.565 degrees would work better as then the four points have X and Y-ordinates regularly spaced along each axis, so for near-vertical and horizontal lines (where aliasing is arguably worst) it is of the best quality you can do. OTOH NVidia and ATI might have decided to use 45 degrees for some perverse reason I am too stupid to comprehend... Or maybe I should patent the angle "26.565 degrees" and sell it to them [edit] Found an in depth article on this http://www.3dcenter.org/artikel/mult...g/index6_e.php with some pictures: Last edited by Stephen Brooks; 5th Jul 2005 at 01:08.

5th Jul 2005, 08:52	#19
drb What's a Dremel? Join Date: Jul 2005 Posts: 1	An example of a difference between ATI and Nvidia is the fact that ATI implement gamma-corrected AA on all their 9700+ cards, a technique which samples alpha particles inside triangles as well as gamma particles on the outside of triangles. This is only implemented by Nvidia on the 7800 GTX. Gamma particles? Is this some sort of inside joke? I think you have perhaps simplified too much ... Multisampling does not require samples to be shared between pixels. Its an approach some vendors use to try to get better image quality. It's misleading to say mipmaps are lower-quality distance textures. They are multi-resolution texture image sets (pyramids) used to approximately match the variable resolutions needed for different object scalings by choosing the closest matching (or pair of matching) images. You probably meant that, but it's not what the article is saying ...

5th Jul 2005, 10:53	#20
Zidane Hypermodder Join Date: Apr 2004 Location: At my desk. Posts: 687	very nice article. explains without confusing. gives enough information to inform, without being too technical, and gives the reader many avenues to explore if they want to know more. __________________ You dont need a reason to help people. `Zidane Tribal. Bit-Tech Folding@Home Team 33346 -> here Join the Bit-Tech Folding@Home team -> here need a hand joining or setting up? ask us on the bit-tech forums -> here