Nasty Artefacts with Architectural Materials

[Caveman]

Hi, in the Architectural material, I can't enable both the "Transparency color" and the "Enable falloff with End color" without getting these nasty artefacts. Any known reasons I might not be aware of with the Architectural materials in Softimage?? With the same settings in Maya I got nice results but something's wrong in Softimage. Any help???

The Second Image is from Softimage and the First Image from Maya.

Edit: The material used in the second image is the Architectural Material in SI. And they are not NaN, they are noises in the transparent areas which was later solved by increasing the min AA Level.

The first image is from Maya. Smooth results without any noises with low AA set to -1.

[ActionArt]

From the images above, I'm not quite sure what you're trying to show.

Several people have reported strange behavior with Arch. material in 2011+. Try using the MR equivalent and see if you get the same results. It seems to work fine.

[Caveman]

The problem is solved by increasing the Min AA Level to 2. Not good cos it increased the render time. I am getting silky smooth transparency renders in maya with min "-1" AA.

While tweaking the mia_material got some black thingy

Recently I am getting exposed to a lot of MR bugs in Softimage. Hope the Softimage 2012's integration with MR 3.9 will be a better one.

Both the images bellow are rendered in SI and both have the same mia material. The second image was rendered with "Min AA Level 2"

[ActionArt]

Ya I see what you mean. I haven't run into this yet but maybe someone else has a workaround.

And lets hope that all the time MR had to work on 3.9 they actually did something

I was hoping that when Nvidia bought them they'd put the boots to them and get some results but it doesn't seem to have had much effect yet I'm afraid.

[Caveman]

Ya I see what you mean. I haven't run into this yet but maybe someone else has a workaround.

And lets hope that all the time MR had to work on 3.9 they actually did something

I was hoping that when Nvidia bought them they'd put the boots to them and get some results but it doesn't seem to have had much effect yet I'm afraid.

And I am afraid that I will have to use Maya more than Softimage because of that
Arnold needs to be released soon or else....

[Maximus]

can you share the scene? i dont think its an AA problem

[Rez007]

I don't think it is an AA problem either. I use the Arch shader a lot and I never ran into that. Is there a possiblity that you have a "double mesh" that you might have accidentally copied the mesh and now two faces are sitting where every one should be. That has happened before to me, if you press ctrl+D in poly mode and then you want to undo it and you don't go back enough steps. The reason that I mention this, is that with a low AA the sampling calculations will have trouble with the double faces, where as the problem, you say is fixed by upping the Min AA to 2 (which is quite high), which should result in Mental Ray possibly discerning the correct calcualtions which makes it look right. Again, I can be way off here and it might not even be correct, but it popped in my head while reading your post, so I just wanted to share.

[origin]

post a scene and stop this nonsense about using maya over xsi because you can't setup your material/sampling properly

[caledonian_tartan]

i've had those black dots too. i had some glass shatters with the archi-material. i think the appeared when tuning the non glossy refraction samples (optimization tab)...

[Caveman]

post a scene and stop this nonsense about using maya over xsi because you can't setup your material/sampling properly

Oh yeah?? Here you go. This is the file. This is with the Architectural Material not the scene with the mia_material, cos I didn't save it. And these black dots look likes the one from the second image not the third image.

P.S-Just kidding about getting angry. Actually I am quite happy that you guys are trying to help. Thanks:D

[origin]

Goto your architectural material, optimization->refraction Cutoff change 0,01 to 0,001 or smth.

[Maximus]

You have a problem with the BRDF+Backface culling + trace depth cutoff + transparency
i've uploaded the scene with the changes, i've changed a bit of stuff, gamma, photo exposure, render region set on global etc but anyway, your problem was mainigly the backface culling option that is turned off by default, this should be on when you are using transparent materials, otherwise it creates that problem, its kinda tricky.

If you are not using a transparent material you should turn it off, try to do a test with a non trasparent and a transparent material and switch it on and off, and check the teapot handle near the cap, you'll see the difference.

The other problem with the falloff is the cutoff treshold radius, put it at 0.001 and you're done
here is the scene
In t he BRDF tab you used 0.01 in the facing reflectivity, keep in mind the mia_material or architectural are meant to work physically correct, and this value is kinda wrong (unless you are going for an artistic or specific look), you should never go under 0.1, check out the help for this.

here is my render with all those fixes:
facing reflectivity 0.01:



here is with 0.1:



and here is the scene

welcome to MR world, ask further if you didnt get something! hope this helps

[Maximus]

by the way, just to add something, the backface cull as you might have seen from my pics is hiding the interior part of your geometry to the facing camera wich sometimes is just fine, but in this case as you see the teapot is kinda rendered wrong (i mean the handle and the cap seems detached), in my opinion the real issue here is your BRDF value added to the cutoff parameter, for a physical glass it should be set to "By IOR"

here is a new render with backface culling back to off, with BRDF set to corresponding IOR, and the cutoff down to 0:



and here is the scene

[schyzomaniac]

Hi
I think you can get rid of that dithering artefact by lowering your Cutoff values for refraction and reflection to 0.
You can find those settings in your arch material under "Optimization". The default value is 0.01. And I think internally Maya uses higher sampling settings than SI when reaching this treshold value. Let me see if I can find a description Zap gave me when I run into the same issue when dealing with Area lights in SI.

cheers,
Daniel

[Caveman]

Goto your architectural material, optimization->refraction Cutoff change 0,01 to 0,001 or smth.

I don't think the cutoff has anyhting to do with these noises. I assume you already know what Cutoff does but I will still define it for others who might be reading this thread and do not know what "Refraction Cutoff" does. Simply put, the cutoff will literally, cutoff any Refraction ray that is contributing less than the amount of percentage that is specified in the Cutoff field/slider(whatever). To prove it, I have attached a rendered image. When the cutoff was 0.01, any rays contributing less than one percent(which in this case probably there were many rays that had less than one percent contribution) was ignored and hence the dark render on the left side, compared to the one on the right side with .001 which is brighter.

This is the first file that Maximus had attached with his example but I just turned off the Backface culling.

[schyzomaniac]

Here is what I get when just opening your file and changing cutoff to zero.