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major antialiasing issue in object ID rpf/exr renders

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manojit ghosemajor antialiasing issue in object ID rpf/exr renders
by on Dec 18, 2009 at 1:57:48 pm

hi
here is the situation:
i have a scene with a multiple object model.
and i have assigned a particular object IDs to each object. and as well as different materials to each of them separately (with separate channels in their respective material ) and rendering out rpf images with objectID/material ID enabled.
the problem:
both the material ID/object ID channel are coming out with huge aliasing on the edges, though the rgb channel is perfectly antialiased.
same is happening with exr format
am i skipping some thing!?
any suggestions/solutions would be highly appreciated.


MG


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Tiago RibeiroRe: major antialiasing issue in object ID rpf/exr renders
by on Dec 18, 2009 at 6:10:17 pm

you are using render elements to export do object id and material id right?
in the element export option, you have a checkbox for filtering. that is probably unchecked
in the render elements dialog, select the objectid element, and scroll down the dialog until you find that filtering option. do the same for material id


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Yeison RuedaRe: major antialiasing issue in object ID rpf/exr renders
by on Aug 4, 2010 at 2:04:37 am

I've tried that option, but the Object ID channel cannot be antialiased, so I'm another one with the same question, I've tested the G-Buffer Coverage, but it has issues and just doesn't work right when an object is in front of other. Thnaks for the help of somebody ...


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Tiago RibeiroRe: major antialiasing issue in object ID rpf/exr renders
by on Aug 4, 2010 at 3:41:00 am

you can also try a trick. my idea is that you can do a 2-pass render, first to render everything except mat/obj IDs, then another one to get only the mat/obj IDs. the first render will be as usual, and the second will be a high-resolution render which you will then downsize in order to simulate the supersampling (and thus antialiasing)

- render your scene normally without caring for the object/materialIds
then disable lighting, shadowing, reflexes, etc, in the render dialog (disable lights one by one).
- set mental ray's adaptive supersampling to 1:1 (although i'll guess that he won't be supersampling the gbuffer..but it's just to be sure)
set the render resolution to something like 4x4 the original (if you are rendering 1280x720, set it to 5120x2880)
you'll basically be doing a 16x supersampling over the whole image.
- render everything and save your object/materialIDs as png files (do you really need these as rpfs?)
- use photoshop or something to reduce the pngs back to the size they should be
sounds farfetched, and it depends on the possibility of you easily rendering the image as a huge resolution, just to get the high-res mat and obj IDs. but you can give it a try =)

it's kind of crazy, but i think it'll be more accurate than blurring out the mat/obj IDs maps...
although you might want to try that before =)
with a 1 to 2 pixel gaussian blur you might get useable results.


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Tiago RibeiroRe: major antialiasing issue in object ID rpf/exr renders
by on Aug 4, 2010 at 4:09:24 am

will, i just gave this issue a try, and filtering worked in both material ID and objects ID elements...
are you sure you enabled it correctly? i tried it in both mentalray and scanline, and they come out soft.
anyway, if you continue to encounter that problem, i have tested my solution, and it works perfectly. it looks infinitly smoother than giving it a 0.7 pixel gaussian blur, so i really disadvise you about doing the blur thing.

but again, i tested the "Enable Filtering" option, and worked fine..


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Yeison RuedaRe: major antialiasing issue in object ID rpf/exr renders
by on Aug 5, 2010 at 12:33:48 am

Well , that's a good way of getting the result, by the way, I forgot to say I'm using VRay render, so, lasta night doing experiments y render the element WireColor, it outputs a map with plane color but, antialiased, so, in order to simulate the Object ID channel, I give a black color to the wire of objects that I don't want to have ID for, and to the rest a color, mostly a pure R, G or B. I don't know if this pass is present in Mental Ray, I guess so, and about the RPF, they can be handy for extracting an object matte, avoiding me the job of using filters for isolate a pure RGB map, but in the other hand, they have problems with the aliased borders, that canĀ“t be easyly manipulated ... sorry my english and hope this method be usefull, any comments please !


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