Dusk exterior - look for crits

[jameswelch]

Studio/Institution: JW
Genre: Residential Exterior
Software: 3D Studio Max / Mental Ray
Description:

Hi, I am looking for some crits and comments on how I can improve this image:

 

 

This is a personal project to try and improve my lighting and rendering skills and have based my image on this photograph:

 

http://architecturepastebook.co.uk/post/42420033110

 

I am not necessarily trying to match the image perfectly i.e. some of the textures may differ slightly but I do want to try and create an interesting image approaching photo-realism.

 

Any comments on suggested improvements would be appreciated

 

Thanks

James

Edited June 26, 2013 by jameswelch
Gallery image a bit large

[RyderSK]

Hi James,

 

The original perspective is more wider, giving more space to the left part of building, while making the dominant centilever smaller. It's bit more attractive, and makes your perspective seem a bit "falling".

 

The second thing is too dramatic lightning, exposure of which doesn't seem to match the overal scene brightness. What is your setup here ? The original picture shows the natural way, the building is till quite dark, while the dusk sky is already slightly burned.

 

Your glass materials seems more like opacity glass then truly refractive one. What is your setup ? I would suggest pure black diffuse, very slight fog, IOR 1.545, and full reflection and refraction (pure white).

 

Materials have too strong bump, bump is rather rough, fake effect, it's better to make it really subtle and use specular map to create imperfections.

[jameswelch]

Thanks Juraj, very valued comments

 

The second thing is too dramatic lightning, exposure of which doesn't seem to match the overal scene brightness. What is your setup here ?

 

I've used a basic daylight system, manually setting the sun low in the sky and upped the output of the skylight a little and then adjusted the exposure quite low to try and capture the lights as best I can. I found a normal exposure wouldn't show the lights around the building.

 

I think you are right about my bumps maps and I will reduce these a little, I might also try and choose a less dramatic sky background. Cheers for the tips on the glass too, I wasn't convinced these were working well although I quite like the reflections.

 

I will go and do some tweaking, any other comments are welcome

 

James

[RyderSK]

Ah, that's it then. I would not try to simulate dusk/dawn with daylight system, esp. not the one in MentalRay. I am not if latest MentalRay produces correct IBL, but there is plugin for that, just check on Jeff Paton's block. HDRi is the only way to go here in this scenario. You'll get proper reflections, refractions, lightning and background aligned well.

[Corey Beaulieu]

One idea about the glass material is to use a falloff map for the reflection. Use, as Juraj suggested the pure black diffuse and and pure white for Refraction. If after a test render you want a slight fog, use a 245 white in the refraction. For reflection, un-tick the fresnell reflection and place a Falloff map for your color. In the Falloff set the type to fresnel and set your colors to a 40 (or something low) grey where the map defaults to black and leave the white alone. For IOR you can use anything from what Juraj suggested to 2.2.

 

What this does is create a glass material where there is no pure refraction. I find that standard glass materials (in 3D) have non-reflective points that seem unnatural and this method helps give glass a sense of weight and thickness without the sensitive controls of fog colors and other things.

 

The lighting setup seems wrong for this image, again as Juraj suggested. I would look into something more like an HDRI setup where the sky is doing all the work for lighting your scene and then you can control the rest of the brightness through your F-stop. The comparable image seems to have a way-overexposed sky, which is good, because it allows the rest of the scene to have a nicely balanced light. You will likely want to turn down the intensities of your spot lights so they stay within your exposure range. Also, light tends to come from light fixtures and they are missing which kills some of the realism.

 

Lastly, as to the bump... Juraj is right about using lower values and specular, but for this image I would add in geometry. There isn't much to the scene so I would go ahead and model the boards on the ground and wall and then put together a material as Juraj suggested. I think your drive to raise the bump value is for the gaps in the would, but this increases the subtlety in the grain too and the whole thing breaks down. I would also add in some interior elements like window dressings and maybe a fewe ceiling details.

 

Oh, and lastly, lastly. The alpha fringing on the tree is really apparent. I don't know how you saved out your image, but assuming you used a black background in the render and saved an alpha channel, you should add a light wrap to the tree. It would be dark like it is, but the edges should be burnt like the sky.

[RyderSK]

I see about the non-reflective glass, but fresnel-driven glass always seemed fake to me. I use blend material, where the bellow material is pure glass, and top material (low blending, 0.1 and less) is mirror like glass, basicly glass without IOR, like reflective layer in real glass window panes. Double paned glass panels are also good idea for exteriors, as they multiply and offset reflection slightly.

[Corey Beaulieu]

I do agree about the Fresnel-driven glass, but do you notice an increase on render times when you use a blend material? I've always stayed away unless absolutely necessary, but really have no proof.

[jameswelch]

Ok, thanks loads for the tips. I'm going back and rendering using HDR as suggested but struggling a bit with the glass. I think i've tried what you suggested but the reflections aren't looking too great (this is a really low res render but hopefully you can still see the glass):

 

 

Would you mind having a really quick look at the setup for my glass and see if i'm missing anything obvious?

 

[Corey Beaulieu]

The material looks pretty basic. I wouldn't anything different from your result. I would again suggest the Falloff map or the Blend that Juraj is talking about.

 

On another note though, I would use a dusk sky HDRI for a dusk shot, not a day sky.

[jameswelch]

Cheers Corey, I will have a go at the falloff now. Yeah I know it's probably not the best HDRI, this is the latest evening shot I have at the moment (approx 19:00), will need to try and find a dusk shot

[RyderSK]

I do agree about the Fresnel-driven glass, but do you notice an increase on render times when you use a blend material? I've always stayed away unless absolutely necessary, but really have no proof.

 

Yes you are correct, blend materials basicly double the sampling each time you add another layer, each material gets sampled individually (via VrayBlend for example), so it adds up to render time quite a lot.

[RyderSK]

Cheers Corey, I will have a go at the falloff now. Yeah I know it's probably not the best HDRI, this is the latest evening shot I have at the moment (approx 19:00), will need to try and find a dusk shot

 

Buy one from CG-Source ;- ) There are no better ones, not even Peter's or anyone by FAR. Huge res, not too dreamy and more on the realistic side, and impossible EV range, no gamma alternation necessary.

[jameswelch]

Buy one from CG-Source

 

I might actually look at doing this. I was naively hoping to find a free hdri I could use but guess anything I find won't be as good as a bought one. Thanks again for your input

[RyderSK]

Nothing best comes with zero price-tag :- )

 

I own quite few Peter Guthrie's HDRis, Dutch Skies collection (used in every Hollywood blockbuster, but meh for architectural lightning, just for reflections), MOOFE, Maground, Cg-Skies, etc.

 

Nothing tops CG-Source, impossibly hi (and TRUE, clean) res (16k px), they are mammoth files. I bought just 6 of them, and I can use them for literally any sort of lightning. Altering gamma, saturation and blur in Photoshop I can also get whatever sort of lighting I have in mind, it's endless flexibility and provides always damn nice result.

 

20 euros per each also makes them damn cheap, so wasting time searching for free (there are none in good quality, but if you want some, HDRlabs is the place to go) is kinda pointless.

[jameswelch]

Here's my latest attempt, I am now using a dusk HDR, purchased from cg source as suggested but i'm still not happy with the result. I'm using only skylight in the daylight system which is using the environment to light. The HDR is loaded into the environment.

 

Also I still can't get the glass reflections working very well, i've tried using a fall off map but it seems to make the glass look a bit 'frosty' at certain angles. Would anyone have any suggestions or links to a good glass tutorial I could use? Any other comments welcome...

 

[Francisco Penaloza]

The default Arch&Design glass is as good as you need, if you want to fine tune your reflections you can control it with the BRDF controls then it will work more efficient that a falloff shader.

Blend material will create a coated like glass, you need to fix the Max Trace depth to control the render time thou, but Arch&Design Glass has more controls that you can fix before start doing blends and mixes.

Glass is all about how transparent it is and how much environment you have to reflect, if you notice in your reference image, the lighting is very soft, shadows are minimum and soft and the sky is reflecting with a nice blue tone in the glass, so for your image I will use default values for your glass, accentuate the reflection curve, and play with the exposure of your HDRI to make it a little brighter and get better color in your glass reflections, you should also put some trees around your house, not visible to the camera but visible in the reflections, they also will give you some color variations soft shadows and so, in real life houses are not in the middle of a white box, in your render should be the same

[jameswelch]

Cheers for that Francisco, some good comments there. I will have a go at adding some trees to my environment to create some more interesting reflections / shadows

[jameswelch]

Fransisco, cheers for those comments - I have done as you suggested and I think the reflections are already looking better. This is only a draft render, going to set a high quality render going now. Thanks for youor advice