Dear Mental Ray Gurus!

[royterr]

try this links:
http://www.jupiter-jazz.com/wordpress/wp-content/data/tr4kv2/html/chapter1-FG.html
http://www.lamrug.org/resources/flickertips.html


If it doesn't work, try to decrease your fg max radiusnd ad try to use an AO pass it could mask those arifacts a bit.


Good luck!

[Ash-Man]

I think it also might be due to the number of divisions you have in your walls and celing

try to Increase the number of divisions so it will have enough gemoetry...

[groblus]

Althogh I'm not a MR guru, but you might consider those tips : (perhaps you've already tried them)
- make celiling go through the wall and the other way around (so they do not only touch ath the corners but create something lika a +)
- increase number of divisions especialy at the corners
- create a cube around you "room", so that it shadows the outer side of the walls

Hope it helps
groblus

[dagon1978]

what kind of light are u using?
dont use maya direct with photons, use area light, or at least a point to emit photons at the window ;)

[shrisha]

Thank You very much to everybody for your attention . I almost lost a last hope for any answer :)
Here is my scene http://www.freewebtown.com/shrisha/plane.rar please take a look and tell me what I'm doing wrong.

2Dagon1978 Thank you for helping
There is a two lights in the scene. Spot light for sunlight and point light with zero intensity only for photon emition inside the room. Work's great in Turtle for me with no problem. By my humble opinion is better than use area light, should be faster.
In Your interior tutorial, with a small amount of photons you also had same "photons leaking" but it's gone with 512 accuracy and 500.000 photons. In my scene good result only with 4000 accuracy and 5.000.000 photons. And render time 1280X1024 is 7 hours on two Athlon64 3500. I think may be problem in something alse. I played with everything, radius of photons, radius of FG, tried diferent geometry, etc.

I realy need your help guys. And will appreciate it very much.

[Ash-Man]

had a quick look at your file



A- you will need to divide the walls and ceiling

B- your MAX FG values is %10 of the room size (use a measuring tool)

C- you didn’t put any value for the GI radius

[JulianS]

Dont worry shrisha you aren't the only one.

I have being in the same boat for some time as well. I am hoping one day i will find the answear to this problem. :scream:

In my case it doesn't happen all time, Only about 10% of time.
Here is my example.

[dagon1978]

i'm seeing your scene, there are some errors in the light setup, you're forcing the GI to have a brighten scene, but the right way is to setup correctly the gamma (with the famous linear workflow) or at least to make the tonemapping in post, with exr or hdr.

another advice, dont use the FG with 0 filter, especially in interior rendering, i strongly recommend filter=1 (2 in some case)

i'll send u a corrected scene soon ;)

[bgawboy]

I would use view dependent FG radii units (pixels).

Do the flicks go away if you increase your FG min radius to equal your FG max radius?

This will make some illumination detail go away, but if it does go away, then try adjusting the sizes to fit your room better.

In training, we've been starting with 25/25 FG max/min radii in pixels and then reducing to 25/5, or overall less, depending on illumination detail required for the scene.

[shrisha]

Thank You Julian :) I know, I'm not alone, and I hope that day will come for everybody:)

Thank You guys but I playing alot with FG and definitely I'm sure here problem with GI photons. Now doing another interior with 500.000 GI photons everything okey but with 2000000 a got again same. :(

Thank You Dagon1978, I'm waiting for your corection with impatience! :bounce:

[MasterZap]

Try Zaps Standard Remedy for these kind of artifacts; set the min and max FG radius to the same thing. Yes, I know, directly contrary to all manuals. ;)

And big too.

Try something like, view dependent, and 25 pixels for BOTH min and max.

Lemme know what you get.

/Z

[MasterZap]

Thank You Julian :) I know, I'm not alone, and I hope that day will come for everybody:)

Thank You guys but I playing alot with FG and definitely I'm sure here problem with GI photons. Now doing another interior with 500.000 GI photons everything okey but with 2000000 a got again same. :(

Thank You Dagon1978, I'm waiting for your corection with impatience! :bounce:

Dont shoot more photons - make the photon solution smoother using a bigger photon lookup radius.

Turn off FG and look at the photon solution alone. Is it
- speckles/dots - BAD - increase radius
- kinda splotchy/cloudy - OK - adding FG will smooth that out
- very smooth / extremely smooth - OK or "oversmoothed", may need to reduce photon lookup radius

/Z

[royterr]

Dont shoot more photons - make the photon solution smoother using a bigger photon lookup radius.

Turn off FG and look at the photon solution alone. Is it
- speckles/dots - BAD - increase radius
- kinda splotchy/cloudy - OK - adding FG will smooth that out
- very smooth / extremely smooth - OK or "oversmoothed", may need to reduce photon lookup radius

/Z

you mean photon accuracy

[MasterZap]

I mean the radius in what is the "globillum accuracy" option in standalone mentalray (the .mi file).

What this is called in the UI in different apps varies.

In Maya it's called "Global Illum Radius".

Also, to make sure the radius is used, set a higher "accuracy". Otherwise mental ray will stop looking after "accuracy" number of photons are hit. It's better to set a high accuracy (the maya default "accuracy" (which is really the photon count) of 64 is far too low) and use the radius to tweak, than fiddling w. the "accuracy" setting (which is a photon count).

Also note, the artifacts seen in the top image can also be caused by photon leaks. Check so light doesn't leak in from outdoor geometry that is hit by outdoor light that has a similar orientation to a (very) nearby interior surface.

/Z

[3DsIn]

I get a pretty good result just using masterZaps method without any photons at all..
just FG (radii in pixel size) min/max at 25 and the presample density cranked.. make sure your scene is 1:1
http://www.ryanjhowell.com/images/crapper.png

[bgawboy]

Ahh. Good idea.

The presample density increases the FG density, while you keep the larger FG radii.
You are using the presample density found only on the miDefaultOption/mentalrayGlobals node (don't remember which offhand), right?

I like to present it like this:
Think of the FG max radius as a filter in the shape of a circle that is passing over your image. The radius gives you the size of that filter. So view-dependent pixel size can be very intuitive when using this way of thinking about it.

Now the FG density can be used to increase (or decrease) the amount FG points seen within the same size filter circle. It will increase (or decrease) the average number of FG points used in interpolation (as reported in the Render Output window).

Bottom line. Even though you might choose a large filter circle size, such as 25 pixels in radius, the increased density may give you more apparent detail without having to reduce the size of the filter circle. (Or first, reducing the size of the min radius to something like 5). This may not work in all scenes, but it is worth giving it a shot to see if it matches your desired visual goal.

[bgawboy]

BTW, I hope you all notice the obvious benefit of the larger FG radii. Speed!

[YourDaftPunk]

You are using the presample density found only on the miDefaultOption/mentalrayGlobals node (don't remember which offhand), right?
Is this the easiest way? I put these two mel lines onto the shelf:

select miDefaultOptions;
ShowAttributeEditorOrChannelBox;


I'm changeing the presample density this way:
(which only works after accessing the miDefaultOption node in a new scene)

setAttr miDefaultOptions.finalGatherPresampleDensity 10;

Why are these settings not in the regular MR Render Globals?

-shawn

[bgawboy]

That is one way. I usually do it through the AE UI, after I select the miDefaultOptions node.
Look under extra attributes at the bottom.

Some of the not-so-fully productized features end up in this limbo state where they are not in Render Globals, but are included, in this somewhat hard-to-find place.

In either miDefaultOptions or mentalrayGlobals node, you also have the very useful Render Mode, that can do an FG map creation only render pass.

BTW, 10 is an enormous density factor. Typically, I use 1.5 or 2, or at most 3. But then again, I might be starting out with a higher density based on my FG radii settings. Use FG diagnostics to see how dense they are.

[3DsIn]

View dependent FG seems to be a very slippery slope, but, you really can't deny the speed increase for this particular scene.. Here are some stats from my bathroom scene:
w/: area lights, glossy reflections & transparency

FG rays = 100
view radii in pixel size = true
FG min/max = 25
Filter = 2
FG secondary = 2 2 1
FG presample density = 2

FG calculation time: 8:00
Render time: 7:56

rendered on:
dual xeon 2.8
3gb of RAM

[MasterZap]

I'm a huge fan of presample density 0.1 and let mr's adaptivity take care of the rest.

But as I said, I'm backwards in these respects. ;)

/Z

[dagon1978]

I'm a huge fan of presample density 0.1 and let mr's adaptivity take care of the rest.

But as I said, I'm backwards in these respects. ;)

/Z

this can be a good idea, density 0.1 and increased FG rays... the only problem can be the FG points added at rendertime, especially with glossy shaders... but i could be wrong ;) i have to make some tests, thanx for your help Master&Bart! :thumbsup:

[Fireantz]

I'm a huge fan of presample density 0.1 and let mr's adaptivity take care of the rest.

But as I said, I'm backwards in these respects. ;)

/Z

sorry about my idoit.......:sad:
where is the "presample density setting" ? what is this setting mainly use ?

[pepino-oni]

type in the command linethe following:

select miDefaultOptions;

and that`s it. I could not find it in other way too.

[shrisha]

One stupid question.
When view radii in pixel size is enable, and picture size is 800/600 (for example) that means 10% for max FG radius is 48000??? Looks like I miss something :)
Could somebody explane me this point, please?

[Exo7]

No, you're doing the wrong math; in fact there should be no math at all !

"view radii in pixel size" <- take the sentence as is, and forget the 10% paradigm then. If you work in scene size, you can apply the basic 10% rule, OR you work in screen space and you decide wether the radius will be 1,2 or 10 pixels wide. Just like that !

My general settings in pixel size for instance (not so optimized):

0.7/1.33 min/max

[shrisha]

If you work in scene size what is the basic 10% rule??? :) And if there is no math at all, why everywhere is talking about this 10%???

[YourDaftPunk]

Shrisha, there are two ways to control the number of Final Gather rays MR shoots into your scene. The 10% rule refers to the first and original way. You would set your max radius to 10% of your scene's longest dimension and your min radius would be 10% of your max. If my room was 20 maya units wide, I'd set it to max = 2, min = .2 as a good starting value.

People now tick view dependat to set the radius based on pixels- the other method. If you do that, a setting of max = 10, min =1 will have the same effect between different scenes: even if you our rendering rooms 200 maya units wide and 5 maya units wide. Mental Ray scales the radius for you.

[Spacelord]

So since view dependent is based on pixels.
It seems to me if your doing tests at a low
resolution, like 300x250 then do a large render 1500x1200
you will have to adjust the min and max radius again ?
for the large frame ? Is this correct ?

[bgawboy]

You shouldn't have to change anything when dealing with pixel units.

That was the whole point of it. It's kind of like your point only twisted around a bit.

If you use scene units, and you change resolution, then you may have to change
FG min/max radii. Using view (pixel) units helps avoid this issue.

[maxwater]

@ bgawboy mhhh... im not 100% sure about it....

I think it is just he other way. when using "View (pixel radii size)"
you have to change it for rendering in different resolutions.

when using scene units (they doesnt change. doesnt matter which resolution you render)
you dont have to adjust them.


correct me, if i am wrong


greets,
maxwater

[ghostlake114]

Yes, when using View radii mode, it s not scene dependent anymore

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