View Full Version : Basic Aliasing issues...

03-10-2003, 11:13 AM
I am new to the forum so Hello out there. Throughout my relatively short tenure with Lightwave, I have been plagued by Aliasing issues. My problem can best be described by a current project whereby the camera is moving slowly through a room with a tiled floor. As the horizontal lines between tiles grow closer together with distance, there is an awful amount of "buzzing" , or a moire pattern that is distracting.

I've spent quite some time trying to find the best combination of field rendering and aliasing settings (upper for our Avid, lower for our Accoms) and have had success when it comes to the smoothness of my objects motions. Yet thin lines, especially horizontal, still play very noisily.

I haven't seen much communication about this issue where I've looked in usergroups. Is there something I'm completely missing about rendering video animation.....Is there a certain amount of noise that just has to be lived with in going to video or is there something besides field rendering to consider?

Potential responders can take note: I typically render TGA sequences; field rendered and interpreted accordingly in After Effects, then out to an Avid

Any and All Advice is Welcome!

03-10-2003, 11:54 AM
I don't have LW but work with Aura with the same results. Adding the right degree of motion blur usually corrects this.

Paul Fierlinger

03-10-2003, 02:26 PM
Thank you Paul for your advice. Both normal and dithered blur have failed to reduce flicker, as have attempts at "sharpening" the objects edges in the properties panel.

I am attaching an image of said scene, to better illustrate the problem I'm having.

Note, the tile is not a procedural, it is a lattice object laid just over the edge of the floor. This was built this on purpose for later in the animation.

Any and all advice would still be greatly appreciated!

03-10-2003, 02:35 PM
Is your floor an image map?

If it is, I've run into similar issues. What has worked best for me is tweaking the Strength value that is next to Pixel Blending and Texture Antialiasing in the surface editor. Usually, a value of about 2.5 is good for me. If you go much higher than that, the image starts getting fuzzy.

Hope this helps.

03-10-2003, 02:43 PM
Its not an image map, rather one object on top of another....but I'm getting desperate enough to try an image map....and your response gave me some ideas for another project that's had problems.


03-10-2003, 03:40 PM
WHat Antialiasing level are you using? Generally i use Enhanced Medium unless im just doing a quick test render, takes longer to render but its the only way to get rid of the jaggies.


03-10-2003, 03:52 PM
I had been under the impression that enhanced low was as good as it gets for video....but since I'm using motion blur now as advised above it could be limiting the blur's potential. I will try enhanced medium.

Any thoughts on further issues such as dithered vs normal w/ field rendering......or sharp edges on objects.....or After Effects interpolation?

Thanks everyone for replying, keep the good words coming....

03-10-2003, 10:31 PM
My experience in dealing with interlaced NTSC video for 20 years has taught me, anytime a perfectly horizontal line approaches the width of one horizontal scan line or less, it will flicker. It is the nature of video and the fielding process. To avoid the issue you can try techniques like blurring and anti-aliasing but often with other undesirable effects. Other things to try might be: introduce some amount of angle between the camera and the line, widen the line, lighten the contrast of the line, dirty up the line so it is not so perfect, use depth of field to add blur to only the distant parts of the picture where the line begins to flicker, use fog, remove, reduce or reposition the direct lighting in the distance.

Anti-aliasing will not have any affect on a perfectly horizontal line. However, even the slightest angle could be enough to trigger the anti-alias filtering.

You may have some luck with using a video de-interlacing technique on your finished interlaced piece. There are some packages that can de-interlace selectively based on the amount of difference between fields, in this case the flickering lines.

03-11-2003, 05:12 AM
With regards to motion blur, motion blur requires quite high antialiasing to produce the best results, this is due to the fact that motion blur is generated by rendering each antialiasing pass in a slightly different position (if its rendering frame 10 for example it would use the position the object was in at frame 9 to work out the blur, ) its kinda hard to explain :)


03-11-2003, 08:40 AM
Thanks to everyone who has replied....

I have some options to work with now, but what's most important is that I have a better idea of what the limitations of video are....namely that a flat horizontal line getting as small or smaller than an actual scan line is just bad news.