Sky bitmap with daylight system

[Dave Buckley]

Hi guys another query that i hope people can help with

 

i have a fairly decent light setup for an exterior that i am practising with

 

however, i want to keep this light solution but use a sky bitmap in the background so i have clouds etc.

 

the scene is setup with a daylight system mrsun mrsky mrphysicalsky photgraphic exposure

 

i believe you can place bitmaps in the haze slot of the mrphysical sky but this doesn't seem to work

 

i have attached the original render and below is a link to the sky texture i am using

 

http://mpan3.homeip.net/content/resources/sky/dayfair.jpg

[MasterZap]

If you want to put the sky bitmap in the haze slot, read this. You need to turn it's output up to around 10-ish.

 

If you just want to use it as an actual background image, well, then just use it as a normal spherical environment in the environment map (remove the physical sky completely), or, if you only want it as a background image, use it in the "background" slot of the physical sky itself. Either way, you should also read this to understand that you need to turn it's output level up approximately 2500,0

 

/Z

[Francisco Penaloza]

puting a sky image with the Mr Combo sun and sky it is a very pain in the but, but there is some work around, normally I put the sky in post but if you want an animation I rather put a dome sky and make a work around that Jeff Patton explain here.

If you still want to use the image map in the mrsky you have to pull way up the RBG values of the image, remember that Mr Sun and sky use "a lot" of illumination and with the photographic exposure it is more evident, so your image must have the same "output" values

[Francisco Penaloza]

If you want to put the sky bitmap in the haze slot, read this. You need to turn it's output up to around 10-ish.

 

If you just want to use it as an actual background image, well, then just use it as a normal spherical environment in the environment map (remove the physical sky completely), or, if you only want it as a background image, use it in the "background" slot of the physical sky itself. Either way, you should also read this to understand that you need to turn it's output level up approximately 2500,0

 

/Z

 

LOL right after I did my post I saw yours, and I was reading your black rendering problems in your page !!!

glade to see you around here Master!!

[Dave Buckley]

ok in the image i posted i had the settings as described, i then made one change and that was putting the bitmap in the haze slot, i sat the haze value to 1 and the output level on the bitmap to 10, the bitmap was only just visible but it was also not projecting the true colours it did when viewed in a normal windows picture viewer????

 

i then tried with a skydome and just a mrsun, everything works but i had to select unitless on the photgraphic exposure and up the value of that otherwise the scene rendered black, and also the mrsun was having no effect even tho i had used ray switchers on the mental ray material etc, with me selecting unitless on the exposure control would i then need to up the intensity of the mrsun to get it to have an impact on the scene?

 

thanks for the help so far guys

[Dave Buckley]

also i am having difficulty getting my head around altering the settings of the daylight system so that the sun intensity, position etc matches that of the sky bitmap, if i use a sunset bitmap, would i need to reduce intensity (mulitplier) of sun and sky and obviously the time, and would i need to alter exposure control settings to accommodate

 

how do you guys go about this??

 

eventually i want to render out various images of the same building at different times of the day but i want to use sky images as the sky rather than the physical sky. i also want it to look as photorealistic as possible.

 

what are your general workflows for this kind of process?

[Dave Buckley]

any more follow ups on this guys??? struggling quite badly

 

really want my renders top notch so all the help is much appreciated

[MasterZap]

ok in the image i posted i had the settings as described, i then made one change and that was putting the bitmap in the haze slot, i sat the haze value to 1 and the output level on the bitmap to 10, the bitmap was only just visible but it was also not projecting the true colours it did when viewed in a normal windows picture viewer????

 

Of course not; the whole point of the "haze" method is to simply use some *picture* of clouds to drive the haze. The only thing used is the shape of the clouds (derived from the brightness levels of your photo - you may need to play with contrast in some cases). The colors come from the physical sky simulation that uses different haze values for different directions in the sky, hence generating a "faux claud" result.

 

It's not true volumetrics, of course, but it's pretty nice because it follows the color over time-of-day, and gives you the visible sun disk for free.

 

i then tried with a skydome and just a mrsun, everything works but i had to select unitless on the photgraphic exposure and up the value of that otherwise the scene rendered black,

 

I never said to use just the mr sun. You should still use the mr sun and mr sky lights, only you replace the environment shader with your sky image. So only the "visible" component of your sky is swapped out for your photograph.

 

and also the mrsun was having no effect even tho i had used ray switchers on the mental ray material etc,

 

Why would you use ray switchers in this case!?!

 

You have two options with a "sky background photo"

 

a) Keep using the mr Sky as lightsource

OR

b) Use the "Skylight" as sky lightsource, set to "Use scene environment" mode, multipleir 1.0

 

In either case you must make sure the physical intensity of your "background photo" matches that of a sky, which you by turning up your sky bitmap's "Ouput Level" - or - as you tried - by playing with the "physical scale".

 

My blog is shock-full of explanations on this topic.

 

with me selecting unitless on the exposure control would i then need to up the intensity of the mrsun to get it to have an impact on the scene?

 

Unitless/Physical mode only impacts "non physical" things (in a practical sense), i.e. whatever this is set to, doesn't impact the suns contribution, because the sun has a fixed physical interpretation at all times, and the exposure control treats those physical values with the physical exposures at all times. The unitless/physical switch is for any non-physical properties, like non-photometric lights, and, also, including your "background image".

 

/Z

[MasterZap]

also i am having difficulty getting my head around altering the settings of the daylight system so that the sun intensity, position etc matches that of the sky bitmap, if i use a sunset bitmap,

 

That's why the easiest way to achieve this is through the "haze trick". Yes, you do not get "perfect" clouds (nothing volumetric or thick), but a very nice "faux cloud" look, and it follows your time of day automatically and gives you a sun disk for free.

 

Also, by the way, I just attended a lecture by an architectural photographer. They say they avoid clouds at all cost, and if one sneaks into an image, they paint it out in photshop...

 

Ain't the world fun?

 

/Z

[Dave Buckley]

thanks a lot for your help zap

 

when i mentioned using a rayswitcher on the skydome, i was following a workaround described by jeff patton, where he talks about applying a bitmap to half a sphere that encloses the scene. it can be found on his blog.

 

i eventually got it to work

 

all i was worried about was trying to match the daylight system to that of the different bitmaps i had for different times of the day.

 

but with your help i am nearly there.

 

i am also looking for a best practice when it comes to gamma settings for p/graphic exposure and whether they should be changed when using logarithmic exposure.

 

the reason for this is that when i do make a render using a sky bitmap, the colour of the bitmap in the render is not the same as the original bitmap file?????

[pixelperfectg]

i was following a workaround described by jeff patton, where he talks about applying a bitmap to half a sphere that encloses the scene. it can be found on his blog.

Hold on there...my skydome tutorial isn't a "workaround" for anything. As I mentioned in that blogy entry it's merely a tutorial for people that have those skydome type maps that work best when mapped to a half-dome mesh.

[Dave Buckley]

my sincerest apologies jeff

 

i didn't mean a "workaround" in a "cheat" kind of way

 

more a workaround in another way of achieving what i wanted

 

[Dave Buckley]

also jeff while i'm here i may aswell fire another question at you as per usual

 

the polar bear style fur that appears on one of your random renders on your blog is amazing?

 

now any tips or upcoming blog posts relating to fur???? preferably big fluffy rugs for luxury apartments

 

i do have your rug material which i love and use for masses of grass but for a close up of a fluffy rug that polar bear fur would be perfect

[Dave Buckley]

ok so i am now doing my exteriors using jeff and zaps help, but primarily the following the tutorial detailed by jeff on his blog with the skydome etc

 

however in the attached image you can hopefully see where i am having problems

 

everything works fine apart from the skydome doesn't show up through the glass as you can see

 

is there something i am still missing or is this a problem with this method???

 

the glass is the preset arch and design glass for window panes

 

p.s. ignore the horrible bush, was just there to give a bit of colour before i populate with real vegetation

[Justin Hunt]

You may have to drop the rayswitch shader into the diffuse slot of the glass, instance the skydome map into the refraction slot,

 

JHV