[Ernesto]

The following wish, was written on a wrong basis. At that time I thought AGS was created to accelerate the rendering process specially slow for glass materials. This was true sometime, but it is not anymore since the release of V1.1. I had learned that Real glass was to slow during beta, and decided that the only way to use glas was AGS, and never came back to see it this was modified.
Now you can render AGS or a double face glass model with a full glass with refractions reflections and so, in the same rendering time at the same sampling level at the same quality!
It is true that AGS has certain limitations but since rendering real glass has no limitation at all, AGS seems to be not necesray. At least not as necesary as it was in the Beta age!
If you do not know the way to create real glass models, read the answer by DJill

Ernesto

I wish it could be possible to disable the atenuation distance.

Here you have a short explanation of the reasons.
I have been working with AGS materials because, lots of models for architectural use have single thin faces to represent glass.
The new material wizard guides the user to the process of creating AGS.
You can choose a color or just transparent AGS.
What the wizard do not explain is that the colour that you can choose is for the reflectivity only.
There are some complex glasses in the industry that combines colours into the reflections, but this is not the standard. Generaly a glass has a colour that can modify what you see through its transparency, but reflections are mainly white, in other words without colour.
Curently it is impossible to create such a glass material in Maxwell to be used with single faces models. The main obstacle is the atenuation distance that cannot be set to zero.
If you want to create a colour AGS material, it should be needed to set an atenuation distance to zero, otherwise there will not be any control, on the glass colour, since it would deppend on the distance at which the objects seen through it, are placed.
I do not know if this could be a phisical contradiction or an impossible task from the mathematical or phisical viewpoint, but it would be of great help in order to simulate Architectural Glass.

Heope it could be possible!

Ernesto

[Mihai]

You can try changing the weighting and color of the reflective bsdf that is part of this material. The other bsdf is completely invisible since it's transmittance is set at 255. It wouldnt matter what attenuation distance it has.

[Ernesto]

Thanks Mihai, but that is not what I need to simulate.
I know the only way to add colour to a current AGS is the one that you descibed, but that is not simulating a colored glass, but a colored reflection.
The standard glass material, that I want to create, has colour in its transparency but has white reflections, but it is not possible right now.
If atenuation distance could be set to zero, then it will be possible.
Ernesto

[Mihai]

The attenuation distance of which bsdf in the ags material?

[tom]

The standard glass material, that I want to create, has colour in its transparency but has white reflections, but it is not possible right now.

It's possible, it's the real physical glass all you need and it has nothing to do with AGS. You simply need to use a glass materal.

Here's an example by Mihai:
http://mxmgallery.maxwellrender.com/ran ... id=268#268

If atenuation distance could be set to zero, then it will be possible.

Anything having 0 attenuation would be opaque and physically nothing has 0 attenuation. Maybe 0.000000001 but not 0. If you mean uniform coloring without taking care of thickness, it's also not physically correct.

[Fernando Tella]

If you want to create a colour AGS material, it should be needed to set an atenuation distance to zero, otherwise there will not be any control, on the glass colour, since it would deppend on the distance at which the objects seen through it, are placed.

I extract from this sentence that you are making glasses without thickness. I haven't tested it but I imagine that the effect of the attenuation would be infinite if there's no thickness (maxwell doesn't know where to stop the effect of the attenuation). The effect of the attenuation depends on the thickness of the glass, not the distance at which the objects seen through it are placed.

[Ernesto]

Yes Fernando,
Perhaps I should explain more in detail: Here you are:
I am using thin faces (not volumes) to simulate glass in a building windows.
Tom, I know it is possible to create a glass material like that, but in this case the option of using a real glass is not possible since the rendering time is increased more than I can wait. I am using a SL of 13 which reaches to a decent result using AGS, but I get black glass panels if I use a real glass material, and double faces to simulate them in the 3d model.
Currently I am waiting 17 hours in a dual core Athlon of 3800 MHZ 2GB ram.
Having said this, we are limited to use AGS only.
Now AGS has a limitation too. My client asked for a green glass, but this green colour should be viewable through its transparencies, and should not affect the reflections, as normal tinted glass.
If we use the color option in the material wizard, all we can get is a transparent glass, where all the objects vewed through its surface will not be tinted, instead all the reflected light will be tinted.
I am not saying that such a glass do not exist, yes it is possible to create such a glass in real life, but it is not the standard and it will be a very sophisticated and expensive glass to be used for buildings.

To answer Mihai´s question, in order to get the glass we are needing, the tinted colour should be placed in the transmitance property of the glass. More precicely in the Refractive Basic Layer. The problem as Fernando pointed is that, as soon as you change the transmitance colour to anything diferent from white, the atenuation distance gets activated, and we do not have a second glass face that could tell the material to stop the atenuation effect, so this effect will be infinite, and eventually all glases will be seen all black unless the object behind the glass panel is too close to it´s surface. As Fernando said, Maxwell do not know where to stop the atenuation effect!

I hope this is clear enough...

Ernesto

[Mihai]

To answer Mihai´s question, in order to get the glass we are needing, the tinted colour should be placed in the transmitance property of the glass. More precicely in the Refractive Basic Layer. The problem as Fernando pointed is that, as soon as you change the transmitance colour to anything diferent from white, the atenuation distance gets activated, and we do not have a second glass face that could tell the material to stop the atenuation effect, so this effect will be infinite, and eventually all glases will be seen all black unless the object behind the glass panel is too close to it´s surface. As Fernando said, Maxwell do not know where to stop the atenuation effect!

I think you may be confused how the AGS material works. There is no refraction going on there, there is no refractive bsdf in it, only a base "ghost" bsdf which is fully transparent, with no refraction, and another bsdf for surface reflections.

In your case unfortunately it looks like you have to use a real glass material, and make sure the windows have thickness. Then you could make a material which has a tinted green transmittance for example, and white reflections.

Maxwell can't know ofcourse where to stop the attenuation effect of transparent objects, if the object doesn't have any thickness.

[Ernesto]

No, Mihai.

I am not confused, I am just asking Next Limit, to let the user to disable the atenuation distance, for those cases in which we use AGS, instead of real glass materials.
Thanks

Ernesto

PD regarding the so called Refractive bsdf, is you who seems confused.
Please try to use the Material wizard, and pick the AGS option, then accept all the options, and you will have the default AGS matereial with two layers: the fistone called Refractive basic at 100%, the second called Reflective basic at 50%. If you look carefully inside the first layer, you will see the transmitance colour box, where a color should be picked in case a glass is tinted. I do not claim the AGS produces refractions, I just told you where the atenuation distance set to zero is needed. Probably the name of that layer is wrong, but that is another bug in the material editor.
Regarding Tom´s paragraph:

Anything having 0 attenuation would be opaque and physically nothing has 0 attenuation. Maybe 0.000000001 but not 0. If you mean uniform coloring without taking care of thickness, it's also not physically correct.

Yes, you are right: it is not phisically correct, in the same way as AGS material is not phisically correct, but since the AGS material is provided by Next Limit as an option, to reduce drastically the rendering time, it should be complete and unlimited enough, to reproduce a simple tinted glass.

In cases of architectural images it is insane to wait for 3 times the rendering time ( 50 hours ) instead of 17hours, since (as you could see by yourself in the provided image) nobody can see the thickness of the glass in the window, nor all the refractions that happens in 4mm, at a camera distance of 20 meters, and a rendering resolution where a single pixel represents a 2 cm by 2 cm sqare in the real space! (5 times bigger than the glass thickness) What would be the sense of calculating all the refractions that are going on in the glass thickness if you cannot see any thickness in the image?
All this I am writing is not new at all, and these same reasons were the reasons to create an AGS. All you should do is to provide a tool that is fully functionable, not half usable. As far as I know there are no reason to make things uncomplete...

By the way, it is not phisically correct to simulate a bump effect with a bump map. It is not phisically correct to simulate a curved surface with a mesh. It is not phisically correct to create a glass panel with perfectly flat faces. Let´s use common sense! All about rendering is simulating. Nothing can be exactly as the real thing, because it will not be a simulation but the real thing. But that is not a valid reason to build the building in order to take a photograph, to print a brochure. If you do so, the image will be fully phisically correct but it would be a photograph, and Maxwell Render wouldn´t be needed!

Eso se llama ser mas Papista que el Papa!!!
Sorry, I do not know a translation...

[Mihai]

Yes, it is wrong to name that layer Refractive basic, you will see it's transmittance color is always set to full white and nd at 1 (hence no refraction).

What you could try is for the first bsdf, set transmittance color to your tint color, but leave nd at 1. Set attenuation distance according to how tinted you want the glass to look. For a 2cm panel, perhaps attenuation distance of 2 or 1cm is good.

In the second bsdf, which provides the reflections, set it's refl0° and 90° to white, nd high like 20. weight this layer to about 20-30, more weighting will make the "glass" material look more reflective.

I'm not sure if you will still get slower rendering in this case, if the first bsdf is set to other than full white like it is normally.

Remember though to model your glass surfaces with a thickness, even for this material for which you would like colored transmittance. You can't have transmittance without setting a thickness to the model.

[JDHill]

Hi Ernesto,

AGS is not a specialized material created by Maxwell programmers, it is simply a clever use of the physically-based material properties inherent in the Maxwell material system. Here are a few notes on the common AGS BSDF layers, to help explain why changing some of the parameters may bring unexpected results:

1) Refractive basic - models a 100% perfect vacuum. Although it's mainly a question of semantics, I have to disagree about the naming convention. This is a transmissive layer, for which the amount of refraction is exactly zero for all wavelengths. Changing the Transmittance color of this layer to anything but [255,255,255] will nullify its zero-refraction property. It is not a question of Att. Distance, but more that there is no such thing as a 'green' vacuum. The operative parameters:

• Refl0 = black -> 0% frontal reflection
  Refl90 = black -> 0% glancing reflection
  Transmittance = white -> 100% light transmission for all wavelengths
  Att. Distance = 1m -> inconsequential, due to full transmittance
  Nd = 1.00 -> the change in trajectory light experiences when entering or exiting this material is exactly zero. No light is reflected

2) Reflective basic - models 100% opaque glass. This layer is purely reflective; the response curve of its reflectivity is determined by the Nd parameter. Changing the Transmittance of this layer to anything but [0,0,0] will produce a refractive dielectric. This, in combination with the Refractive (vacuum) layer, will cause the material to become a birefringent (posessing multiple indices of refraction) medium. The operative parameters:

• Refl0 = grey [64,64,64] -> 25% frontal reflection
  Refl90 = white -> 100% glancing reflections
  Tranmittance = black -> 0% light transmission for all wavelengths
  Att. Distance = 999m -> inconsequential, due to zero transmittance
  Nd = 1.51 -> no light is refracted, due to zero transmittance. Light is reflected between 25% and 100%, depending on the viewing angle. The Nd value 1.51 reproduces the reflection curve of common glass

Now, taking these factors into account, some experimentation may be done. Here is a quick comparison:

standard wizard-created AGS:


...and here, with a green-tinted Transmittance in the Reflective BSDF:


The side-effect (birefringence) of such a modification may or may not be apparent, depending on the situation. The Nd parameter may also be changed (in the Reflective layer; generally raised, to give stronger reflection), to acheive a desired result. Also, regarding the usage of singe-surface vs. mesh-box windows:

...I get black glass panels if I use a real glass material, and double faces to simulate them in the 3d model.

In the case of a traditional dielectric, they must be boxes -> single-mesh boxes. Separate meshes will not work. In the following image, the pane on the left is a single-mesh box, while the one on the right is 6 separate mesh-surfaces (they are actually the same polysurface box copied, but the one on the right was exploded before meshing):



~JD

[Ernesto]

JDhill, let me complete your description:
It is not necesary to have the 6 faces, it could be donde with only two, but in order to make sure that it will work, these two faces must be a single object/mesh. If each of the two faces are diferent objects or meshes, the real glass material will not work properly. In the following image the glass panel at the left has 6 faces and the glass panel at the right has only two faces.

Anyway I think we are changing the subject.
It seems that there is a strong resistence to my original wish...
But I haven´t changed my mind... yet.

Ernesto

[Ernesto]

I have modeled the glass, so that I will be sure they will be a single mesh.
They are re-rendering since 10 hours, and it needs 8 more hours.
Up to now It seems that it is going to get to the same quiality as AGS in the same time and Sample level.
I must say that I was wrong when thought that the black glass looking was a result of using real glass, and that much more kooking time was needed to get to the same result.
Thanks DJill your info made the diference!
It seems that the software it is used and the way it exports to DXF (in my case) has a lot to do with this.
If I have an exploded mesh in autocad, as soon as it gets loaded into studio they convert to mesh again. It depends on the layers on which the exploded faces are, if they will convert to a single mesh or not.
Thanks Mihai and Tom for your resistence. Thanks this I did another chance to the double faces glass.

I have been asking in some posts long time ago, which was the rule to create glass in maxwell. And now it is the first time I understand it.
I have done two other commercial jobs and the glass on those buildings were wrong. They looked too dark.

Perhaps this is one of the important stuff we should keep in mind, and perhaps written somewhere to warn other users from this same mistake.

Now, my question is diferent:
Which is the sense of using single face glass, since using two sided glass will give a better and unlimited result at the same time ansd same SL????

I do not see the advantage of it at all!
Well just in case you have an old model where the glass is a single face , and if you are too lazy, you can assign the AGS instead!

Yours

Ernesto

[Mihai]

Yes, if your model glass is single face you can assign an AGS material since there's no transparency going on there (in the AGS material).

Which is the sense of using single face glass, since using two sided glass will give a better and unlimited result at the same time ansd same SL????

Who said you should use single face glass?

[Ernesto]

This is the image with AGS at SL 13, rendering time 18 Hours


And this other modeled with double faces glass panels, and real glass material same time and same SL.