WIP - Glass advice please

[tbny]

I am doing montages of a "twisty" type tower. Location and all very hush-hush so I can only show a small bit of the image here.



I am having problems getting the glass to look well for the montage. There are no other really high building surrounding the tower and the sky in the photo is reasonably flat blue (not the sky shown in the image).

i.e. there is not much to reflect of the surroundings but the client wants the glass to be glossy and reflective looking and yet not completely loose a sense of transperancy...

The tower has an outer frameless glass skin and everything else is behind the glass. At the moment the glass applied is vray glas with a perpendicular / parallel fall-off map. I then used a tube with the sky from the photograph applied to it for reflections. The result I am getting is very bland..

I am wondering if there are any ways to improve either in max or in photoshop for this type of rendering. Any help much appreciated

tbny

[dlparisi]

Can you post a screen shot of your glass material?

[beestee]

Maybe instead of a clear sky use something with clouds, or something with a more distinguishable, strong gradient such as dawn or dusk. You could perhaps even try reflecting the sun off of the glass if you are unable to change the sky, just turn the highlight glossiness of the glass down below 1 a tiny bit and you could get a good reflective gradient effect.

[Jonferimonic]

Change your falloff type to fresnel for starters and make sure affect shadows is checked on. This will change how you reflections act and should increase the glass effect you are after. I reckon you should use an HDRI instead of a tube for your sky aswell, you have more control over brightness of the reflections this way.

[tbny]

Thanks for the resonse so far
Here are my glass settings



beestee

I am stuck with the photo as it is. Will try your suggestion with the highlight glossiness and see what happens

Jonferimonic

Sorry my mistake I am using fresnel
Cant really use HDRI since I only have this photo, as far as I know a big pain in the a** to try to make a HDRI from a single exposure photo

[joconnell]

You can pretty much use anything as a reflection in the surface - who's going to know what should have been in front of it - once the reflection looks like it could be the same skyline in terms of time of day / clouds etc. To get really high quality reflections you're probably best off making some invisible planes, put a nice bitmap on it and then set it to invisible to camera and turn off cast and send gi - it'll get the best resolution from your bitmap. I'd say if you used proper glass settings at this angle you wouldn't get that much reflection since it's straight on and reflections are stronger at the side - it's a physically inaccurate result but probably what you want as your end result.

[tbny]

cheers joconnell

what you are describing is pretty much what I am doing except i am using a tube.
the issue is that the contrast between the background sky and the reflected sky is very small and i am lacking any sheen off the glas.
What you say is true that this side of the tower is very straight on and would reflect less but the client wants gloss so........

[joconnell]

I take it in that case that you've been given a photo to match and put the building in to? If it's a case of the sky being quite boring then you're not going to get much in the reflections - what I'd suggest is maybe edit the sky in the photo you're using to make it a bit more interesting - even if it's only adding a few clouds in, just to break up the sky a little bit so you can reflect some clouds in the building. As regards the tube thing I think a cubic map may work better in this case - if the building was cylindrical a tube would work great but for this one I'd go for a box - since the front of the building is quite flat I'd put in something directly facing it - it'll suite the parallel rays of the windows reflecting and give you the best pixel quality in the reflections. As someone else mentioned it might be an idea to use a simple grad and do a similar masked colour correction on the bg photo - anything to take the flatness away from the bg photo - glass object are always going to look boring if they've a flat object to reflect.

something like this mite work better:

[FlytE]

Glass reflection should almost always darker than the sky, even if its only just marginally

I notice in your falloff map your IOR is set at 10. This is pretty reflective and is going to result in you reflecting your environment very strongly. This is probably why you are getting such a washed out effect in your glass. When I do glass, I give it about 65 - 75 percent reflection, not 100, and I balance that out with a simple vray fresnel but increased to something between 2.3 and 3.5.

Personally I would put your reflective subdivisions up to the same as your refractive.... for high quality glass I usually use 50 subdivs for each. Im not sure about the .98 glossiness, I would leave it at 1 but hey.... sup to you. I would also consider not using the fog unless you need to, and even then I recommend its really subtle.

Hope this helps...

[joconnell]

That's quite true but as he said he's going for really obvious reflections so fresnel is kind of defeating the purpose in this case - it's too weak at the front for the strength of effect he wants -I'd say a falloff in perpendicular / parallel is far more controllable since it's a more linearely controllable effect - fresnel is a bit harder to predict.

[dlparisi]

If the suggestions above don't work for you I'd suggest ditching that material and start with a basic black or nearly black material, reflection of white or nearly white with a fresnel reflection and IOR of 2 and a refract color set to a slight blue green (Hue ~115 and 10 on the saturation) and a value of ~220. Check affect shadow and alpha. Leave everything else at defaults. For the reflection, try using the vray sky. While it won't give you the cloud refelctions you're probably looking for it will give you a pretty good variation along the length of tower that matches a real sky. Lastly you can apply a bump map to each pane of glass to simulate the bowing of the planes due to static pressure inside the building. Hope this helps.

EDIT: Another option is just to render out a channel using object ID of just the glass. Use that to get a selection in photoshop and paste on some reflections. Set that layer to linear dodge to 'add' the new reflections onto the rendered building. Adjust the opacity of the layer until it looks right.

[tbny]

big cheers everyone for the suggestions
I will try them out

that twist is driving me crazy, everything is soooo much
more difficult compared to a non-twisty building

dlparisi

your suggestion of bump-mapping the glass is something I have thought about before but being fairly weak in max itself I am not sure how to apply a bump-map to each of the roughly 1300 panes of glass especially since the tower is twisting. To get that effect each pane should have a slightly different bump etc...
Any suggestions there?

[dlparisi]

If each pane of glass is already modeled, put on a UV map and select 'Face'. I'd make a custom bitmap that has light bulge in the center with maybe a bit of noise. For added effect, make a couple of differnt bump maps and disperse them through a multi-sub object and add a Material by Element modifier.

[tbny]

again many thanks
I'll see if I can manage that with my meagre
max knowledge

[Adam H. Stewart]

Interesting design

I have nothing to add on the glass front I think I know where that top secret tower is going. Lets just say if you are from Irish you two might be able to figure it out . Then again I could be wrong.