When wanting a realistic sky . . .

[Dave Buckley]

do you guys tend to add the sky in the 3d package such as using a sky dome??? If you do then do you use a high res bitmap or a hdri so that the lighting matches also???

 

If you just add the sky in post then do you use hdri's or again high res bitmaps???

 

Just wondering what techniques people use to get to a good looking sky replacement, that fits with the lighting and reflections etc???

 

In other words, i want it to look as real as possible?

 

If i was going for extreme realism i would take a guess that the sky used for the replacement would also be used for the lighting in the 3d package??

 

Is this right

[SandmanNinja]

If you want realistic lighting and appearance, I'd go with HDRI. It does both. That's what it's designed for.

 

Having said that, it's not super-hard to take a nice spherical (or hemispherical) sky shot (non-HDRI), map it to a sphere, find the sun and put a light source in the exact centre of the sun in the photo. Your lights and shadows should be spot-on then.

[Dave Buckley]

when using hdri and showing sky in the render? would you still need to map the hdri to a hemisphere???

[Tommy L]

If this is for a still then do it in post. Make sure you render to a format that stores the alpha channel then just drop in your sky and tweak as necessary.

[Claudio Branch]

I would be judicious about using an HDR for the actual background image. It can be done, but you will want to use a really high quality/hi-res image.

 

For stills, I like to take my own photographs for the final background and use the HDR for it's light contribution and/or its presence in any reflective surfaces. For animations though, you cannot use this approach...

[WAcky]

I use a sky dome for reflections and make it invisible to the camera when rendering, then plonk in a sky in post to make sure its just right.

[Dave Buckley]

so if it was for an animation what approach would you take.

[Tommy L]

Ive done a few different things and been happy with them. vray sky environment works well. So does HDRI. The sky is less important with animation as long as the camera work and composition (direction) of the movie is good. Image focus can be directed by the movie maker and so the sky is less of an issue. In a still the eye drifts all over the image and everything gets a close examination.

[Dave Buckley]

all i want really is a realistic sky in stills and animations that looks as natural as possible, so i just thought hdri would be the way forward. The thing with adding the sky in post is that it takes ages finding a sky to suit the initial lighting solution, whereas with a hdri this is eliminated straight away as the lighting instantly matches the sky right?

[Tommy L]

Well yes, but why accept a generic solution when you can have complete control? HDRI skies are problematic because of resolution. A lower res file renders quicker whilst a high res looks better. Now you can put one in the GI slot and one to override the background, but you're still tying yourself to one image to solve 2 issues (lighting and sky). I think the best solution is

1: light the scene in a way that makes the buildings look beautiful.

2: put in beautiful sky that matches lighting.

There's no right way and I dont know your workflow and deadlines. But the above is my method.

[Crazy Homeless Guy]

i haven't had a lot of luck with using HDRI for the actual sky image. There always seems to be a scale issue, but maybe I am doing something wrong.

 

Like other, I have had varying degrees of success with different methods. Mostly I prefer to Photoshop skies because that gives you the most control. Just make sure you pay attention to the angle and direction the sun is coming from, and how the clouds effect the composition of the image.

 

I have used Zap's sky method with success a few times using MR.

 

You might want to scour the Vray forums (if they are back up yet) for a sky thread. I am not sure who posted it. It basically consists of a skydome, with a cloud texture mapped onto it. The blue part of the sky is masked out, so that you see the blue of the Vray sky behind. Then, as you move the position of the sun around, the lighting conditions of the clouds change to match the position of the sun. It is not perfect, but it is an excellent place to start.

 

In animation I like to use a sky sphere, with a map similar to the ones at 1000skies.com mapped onto it. Just make sure that the sun position in the sky map is rotated to closely match the sun position in the rendering.

[Claudio Branch]

In animation I like to use a sky sphere, with a map similar to the ones at 1000skies.com mapped onto it. Just make sure that the sun position in the sky map is rotated to closely match the sun position in the rendering.

 

I use a V-Ray Dome light with an HDR in the texture slot, perhaps I should try mapping the HDR onto a sphere...

 

When doing an animation, I'm usually only interested in using the sky portion of the HDR for my background anyway.

[Dave Buckley]

any chance you guys could post examples where you have used certain techniques to show the results of each technique???

 

so from what i gather its more a case of light the building any which way i choose, but just making sure that whichever sky i use, the sun in the photo and the render must line up basically

 

and i guess it doesn't really matter which way i get the sky in there as long as the factors above have been taken into consideration.

 

i was just worried about my lighting not matching my sky i think

[Tommy L]

only way to find out is to try it!

[Dave Buckley]

ok cheers guys

 

just been looking through a tutorial on the area written by neoscape about exteriors.

 

he mentions using a sky bitmap mapped to a dome as part of a vray light material but he then adds in a sky anyway in post??

 

any particular reason as to why he may have done that???

 

Why not just use the sky you add in post as the texture that is mapped to the dome?

[Brian Smith]

ok cheers guys

 

just been looking through a tutorial on the area written by neoscape about exteriors.

 

he mentions using a sky bitmap mapped to a dome as part of a vray light material but he then adds in a sky anyway in post??

 

any particular reason as to why he may have done that???

 

Why not just use the sky you add in post as the texture that is mapped to the dome?

 

could be to help prevent strange colored edges appearing along the boundary of the 3D objects and what was the background color. could also be because the background dome affects the GI in the scene...quite drastically in fact.

[Dave Buckley]

why does everybody tend to use dome lights and image mapped to half spheres???

 

any particular reasons why people don't use the GI Environment Override??

[Dave Buckley]

i think what i am trying to suss out is all the different ways that we can use a sky hdr to light an exterior scene as i am aware that there is more than one way.

 

For example, for a sunny day exterior, i would probably light it with sun and sky and physical sky as i normally do

 

then i would put the hdri in the reflection slot so that the reflective materials look good for when i come to add a sky later

 

OR

 

put a hdri in the environment slot and add a direct light and add sky in post

 

OR

 

add the hdri to the texture slot of a dome light and add a direct light and add sky in post

 

OR

 

hdri in enivironment and reflection, vray sun

 

OR

 

rather than hdri, map an image and vray light material to half a sphere nd add a direct light

 

 

you get the point, what i am saying is there are many many ways to get the same result, but what are the pros and cons of all the different methods. with me not being an expert (yet ) i find it hard to spot major differences

[Brian Smith]

well to each his own, but i think the best way (imho), is to always use a 3D background rig as described in week 13's article here http://www.cgarchitect.com/upclose/VI/default.asp.

 

as for hdri's, i believe that while you can certainly get nice looking images, their use is most warranted in low intensity exterior scenes...ie when the sunlight is not overpowering the skylight. there's really no hdri illumination that you cant create with real lights, the only question is how long will it take to setup. the lower the illumination, the more difficult it becomes to duplicate the look you can get from an hdri and more difficult it becomes to remove noise.

 

if you do use an hdri in vray, i highly suggest using only with a dome light, as the results will always be much better. not sure about mental ray. don't even consider an hdri in the environment channel an option with vray.

 

 

 

i think what i am trying to suss out is all the different ways that we can use a sky hdr to light an exterior scene as i am aware that there is more than one way.

 

For example, for a sunny day exterior, i would probably light it with sun and sky and physical sky as i normally do

 

then i would put the hdri in the reflection slot so that the reflective materials look good for when i come to add a sky later

 

OR

 

put a hdri in the environment slot and add a direct light and add sky in post

 

OR

 

add the hdri to the texture slot of a dome light and add a direct light and add sky in post

 

OR

 

hdri in enivironment and reflection, vray sun

 

OR

 

rather than hdri, map an image and vray light material to half a sphere nd add a direct light

 

 

you get the point, what i am saying is there are many many ways to get the same result, but what are the pros and cons of all the different methods. with me not being an expert (yet ) i find it hard to spot major differences

[Dave Buckley]

when you say that is the best way in your opinion, is that opposed to photoshopping a background in???

 

What i was thinking of doing was using the standard sun and physical sky and then drop the sky image that i am going to use in photoshop into the reflection slot in the vray environment.

 

that way the scene is lit at the correct time of day as the photo i am going to use and also the reflections match

 

i haven't read the chapter you outlined yet, but i'm guessing that is kind of the same principle but you get the background in the render and also the reflections will then come from that background right??

[Dave Buckley]

just want to say thanks brian, your 3ds max 2009 intermediate to advanced book came through this lunch time and i can safely say i think the chapeter on backgrounds will help me a lot (so will the entire book to be honest)

 

i'm now just going to test and find the advantages of one method over the other, for example, advantage of using half dome over a cylinder etc, and why you have chosen to use cylinder and a dome in one example and what benefits that brings.

 

i guess i don't need to use hdri at all really.

 

i just thought that if i used normal vray sun and sky and then photoshopped a sky in, then the lighting wouldn't match but i guess it won't be that noticable with materials and textures etc on there.

 

with regards to applying a jpeg/light map to a dome i guess that eliminates the lighting variation problem for me and then just add the same jpeg in in post. reason for this being when you increase the mulitplier of the light material the original jpeg blows out, so i could use the jpeg to get variation in lighting, and then add the same jpeg used for lighting in post

 

or something along those lines anyway

[Peter M. Gruhn]

Is anybody using Dreamscape for skies? Comments?

[Billabong]

Is anybody using Dreamscape for skies? Comments?

 

I tried it on an ocean animation I had to do once, but the sky options are limited. Plus you have to use the dreamscape sun in order for the sky to work.

 

Although this was the beginning of last year when I had used it and It was an in house contract job. So I haven't used it since and don't know if they Sitni Sati has made any more improvements to it or not.

 

I read somewhere on here the other day where someone was using Vue Infinite to create their own BG skies and using those on a sphere. I might have a look at that myself

 

 

-B