Catmuul vs Area filter

[craiggorton]

I'm not sure this is a bug or an effect. The first image uses the area filter in the image sampler. The second uses catmull, which I prefer, but it leaves a white line over the horizon. Any ideas why this happens?



and Catmull...

[joe_b]

Re: Catmuul vs Area filter

I'm not sure if thats a bug or just how the Catmull algorithm should calculate the result based on the inputs. Perhaps Vlado could shed some more light on this

[Micha_cg]

Re: Catmuul vs Area filter

Craig, if you like, you could search for "sharpening" and "halo" effect at google. I suppose so, the catmul filter create halos too. Maybe a photoshop sharpener without halo effect do a better job.

Here a link to a sharpener without halo:
http://www.powerretouche.com/

This toolset bring a tool against aliasing effects too. I tested it in the past. Useful.

[dalomar_cg]

Re: Catmuul vs Area filter

Yes thats just one of the side effects of the Catmull-Rom filters. Here's an example page from spot3d http://www.spot3d.com/vray/help/150R...ge_sampler.htm

Personally I like to do AA without any filters and then add filtering in post for two reasons. First is that sharpening filters (like Catmull-Rom) can have adverse effect on render times, and second is that the results in certain situations (your horizon line is one of them) can be less than desired and difficult/timeconsuming to resolve. This gets compounded (both time and results) with effects like displacement, depth of field, and motionblur (although it isn't supported in vfr @the moment). Also if you take care of it in post there is much more flexability as far as the amout of effect as well as the amount of time as opposed to being done while rendering. It is however, up to you. Lastly, I don't use blurring filters very much as the blur detail, but sometimes it can be slightly faster for tests