Transparency through two windows

[Ma3rk]

Tried all the suggestions above, nothing works. In fact I tried all the glass presets. This is just crazy.

I've attached the object without textures as that would've made the file size massive and it doesn't matter whether textures are applied or not. Can anyone see something wrong that I can't? BTW I'm using 2018.0.7 and as I said in my original post the object renders fine in 11.6.3 which to me would suggest it's not a problem with the model, but of course I could be wrong.

I just gave it a quick try in 2019.1.5 with default settings and getting same results as Axis3D. But since you don't have those presets, not much help really.

Have you tried simply dialing the transp to 99%? If that isn't doing it, there's something else very basic amiss.

[adrian]

Well I learnt something new today, always have glass objects on a separate layer. I knew I needed to do that with things I wanted to animate but never with glass. Sadly it still doesn't work in 2018 so I now have to assume there is a bug in this version. I've thickened the glass, put it on a separate layer, given the glass all the different preset surfaces, set refraction options to Raytace + backdrop, Refraction recursion limit anywhere between 3-50, same for transparency recusrsion limit. I also tried converting the surfaces to Principled BDSF and Dielectric. I have used all the glass presets when using the Standard materials.

I tried taking the far side windows away so there is just a hole where the glass should be, I still see a block of white instead of the background image. If I take ALL of the windows away then I can see right through to the background image.

I then created a simple test object - a box with two windows (making sure to apply the principles above) and got exactly the same results.

When looking at the object in Textured Shaded Solid mode in Layout I can see right through the object at the background image fine but when rendering - just white where the far windows should be. I even tried loading the glass as a completely separate object.

I watched Rebel Hill's video (in fact I bought the whole course which is great) and nothing different there from what I'm doing.

Sadly I don't have 2020 or 2019 to try and no doubt see that it will just work as it should. At least though I have learnt some better practices.

[gerry_g]

well having said what I said I opened your carriage in 2019 and had no problems with the settings, yeah I know you are on 2018 but still, I ran that for a year and had no problems with glass objects from what I can remember, are you sure about your result.,Also did a quick test with glass and disable shadows and it seems to make little difference with a glass material like dielectric, I would think the cast shadows thing relates solely to standard with transparency applied, it always used to be the case that you had no light transmission through an object even if you had transparency applied unless you unticked cast shadow

[adrian]

So I just noticed the white is being caused by the backdrop which in this case is the standard background gradient, if I set the background to an image it shows the image on the windows, but of course you can't see through them (the far sided windows that is). This is when I have refraction set to raytrace + backdrop. When set to just raytrace it's just black.

[gerry_g]

I can get good transparency with an all grey BG and no image, don't think that's it, a thought....... sometimes VPR does not update when you swap or adjust materials, sometimes you have to give the timeline a little nudge to get the update

[RPSchmidt]

I would recommend doing a simple test using a different model and scene.

Just go to Modeler and make a cube and a plane. Set the cube on the plain and create a surface for it called "glass".

Open Surface Editor and make the "glass" surface a dielectric. Go into node editor and compare your dielectric node to this one: https://docs.lightwave3d.com/display/LW201Dielectric

Save and send it to Layout.

Create an environment light and delete your default distant light. In your environment light properties, make sure "Sample Background" is checked.

Open up Background and add a Textured Environment. Load an HDRI into the textured environment and make sure it's on the Y axis and wrapping spherically.

In your render properties under Render, make sure Raytrace Shadows, Raytrace Reflections, and Raytrace Refractions are checked.

Under Global Illumination, uncheck Sample Background; check Caustics; uncheck interpolated.

Now take a look at your cube in VPR. It should be transparent, might be partially green. You should be able to see the background through it, though it will be distorted.

If that's all good, scale the cube on the x or z to make it thinner like a pane of glass.

Duplicate it and then set your view to look at both at the same time.

Check it in VPR. You should be able to see the background still through them, but you will have high Refraction Index (index of refraction IOR) that will distort the background HDRI.

If it's all good, then go into the node editor for your glass surface and change the transmission color. The Refraction Index for glass is 1.5, but if you don't like the amount of warping, you might want to lower it. I wouldn't go lower than 1.3.

If that is all good and working properly, then you might have a problem with your other scene or you may want to adjust some of your settings between lighting, rendering, and surfacing.

[Sensei]

I tried your object in LW 2018.0.7, LW 2019.1.4 and LW 2020.0.2.

LW 2018.0.7, LW 2019.1.4 have the same problem,
LW 2020.0.2 is fine.


But I found quick'n'easy workaround for you:
cut'n'paste your windows from 1st layer, to 2nd layer.
Make surface 0% Transparent. Instead adjust Dissolve in Object Properties.
I can partially see through tinted windows this way and see environment and objects behind train.

[Sensei]

I can get good transparency with an all grey BG and no image, don't think that's it, a thought.......

But it is irrelevant to his case, as he is using completely different LW version than you..

BTW, it's "several layers of transparency" but ton of other things...
Let's concentrate on "how to fix his problem in what he has access to".

NewTek fixed it by themselves.

sometimes VPR does not update when you swap or adjust materials, sometimes you have to give the timeline a little nudge to get the update

It is bug in LW 2020.x

[gerry_g]

yes I dumped 2018 a long time ago, only have 2019.1.5 and 2020.0.2, as the error is still in 2019.1.4 that would be why I am not seeing it, but I still say I ran 2018 for a whole year and used glass on numerous occasions without any issue, not to mention 2019, still think the issue relates to volumes or thickness of glass rather than simple planes of glass, its that the glass is acting as a volume that is the problem. Both these were done in 2018, the phone box is single polly layer, the glasses have thickness both render just fine

[Shabazzy]

I then created a simple test object - a box with two windows (making sure to apply the principles above) and got exactly the same results.

When looking at the object in Textured Shaded Solid mode in Layout I can see right through the object at the background image fine but when rendering - just white where the far windows should be.

Hi Adrian,

In your test object, if the box is made up of just six flat connected planes, are you making sure the box set to 'Double Sided'?

Also, regardless of whatever, always check the 'normals' of your geometry are pointing in the correct direction. (Press 'd' in Modeler. Display Options>Layout Tab>Show Normals checked). Adjust 'Fixed Normal Length' to suit your taste.

[adrian]

Hi guys thanks so much for all your suggestions. So.... I downloaded the trial version of LW2020 and....UGHH - IT WORKED!!! As I don't have the funds to upgrade just now I have since uninstalled it but at least that's satisfied my sense of curiosity.

So here's where things get weird (as if they weren't weird enough already) - in the particular scene I'm working on I have a signal box with - yes you guessed it - lots of windows and I can quite clearly see through one side and out of the other exactly as one would expect. Guess what even more? I used "bad practice" with this object (I made it months ago) so the windows are on the same layer albeit separate pieces of geometry in this case. So there must be something about the carriage object and the simple test one I created that 2018 does not like in some way.

Sensei, your workaround works just fine. Obviously I don't get the refraction using this method but for the particular scene the object is in it's not a problem at all.

[gerry_g]

yeah well I reinstalled 2018.0.7 and this is how it went, a cigar to the person who can tell me where the bug is cuz for the life of me I can't see one anywhere, no cheating no mods just the vanilla LWO I downloaded from here ????

[Sensei]

Hi guys thanks so much for all your suggestions. So.... I downloaded the trial version of LW2020 and....UGHH - IT WORKED!!! As I don't have the funds to upgrade just now I have since uninstalled it but at least that's satisfied my sense of curiosity.

Better install it back. 30 days trial will go on no matter if you're using it, or uninstalled it.. So better use all these 30 days of trial wisely..

[Sensei]

Sensei, your workaround works just fine. Obviously I don't get the refraction using this method but for the particular scene the object is in it's not a problem at all.

IMHO you should not use refraction in this project at all..

Imagine, ray hits front window polygon, now it is INSIDE of transparent object, like entire inside of train, then exits transparent object after hitting opposite window (or something inside of train like lamp or table).

So, if you want to use refraction index other than 1.0, you should make window with <= 1 cm thickness, so exit from transparent object ("window") is almost immediate.
Otherwise LW render engine thinks it goes through medium with RI=1.3 (e.g. like when entering water in a box).

RI= 1.3 with just a few mm-cm thickness medium ("window"), with very large object for dozen meters, will be indistinguishable from RI=1.0.

[Sensei]

yeah well I reinstalled 2018.0.7 and this is how it went, a cigar to the person who can tell me where the bug is cuz for the life of me I can't see one anywhere, no cheating no mods just the vanilla LWO I downloaded from here ????

The bug is black color instead of transparent windows..

You cheated, because you loaded glass preset instead of figuring out what is wrong with his settings.

I don't smoke, but you can always buy me whiskey...
(or two, because adrian second )

Here is reason why adrian has issue:

His original settings (Raytrace Only):


After changing to Raytrace + Backdrop:



Why the same object does not cause issue in LW 2020.0.2 ? Because Raytrace+Backdrop option has been removed.