How to Change Background Photo's WEATHER ?

Fauvist

When you're using a background photograph or an HDRI background to surround a house with huge windows - how do you make it look like it isn't a static photograph - weatherwise?  A background photograph or HDRI of a forest or a beach - the clouds stay in exactly the same position, If you need to make a series of renders in a room with huge windows, it looks absurd to have exactly the same image for the background for every hour of the day, and the weather never changes.  Is there somewhere to get HDRIs that are EXACTLY the same location and position, but at different times of day, and with the clouds in a variety of configurations?

Richard Haseltine

You don't - and HDRI is a single, static image not any kind of scene description that can be modified or moved about in. If soemone had extended acces to a location they could create HDRIs at different times of day and in different conditions, but that would require access at the right times and that the person making the sets could set up their equipment in the saem way each time.

Hylas

On CGAxis you can find sets of HDRIs that are the same scenery at different times. S'expensive, though.

Use DAZ' sun/sky together with a cloud system (like this one or this one), and actual geometry for landscapes (like Terradome 3), for more control.

MelanieL

This could help with changing the apparent time of day and maybe the weather (e.g. golden sunshine or grey overcast): Iray HDRI Reshade but you'd need something else for cloud cover.

FirstBastion

If you use the SUN/SKY option in iray you can atleast set different times of day,  thus causing the shadows due to sumlight outside to change as well as the color temperature of the sunlight,  going from a strong tinge of blue in the early afternoon,  to a warmer and redder sun/sky as sunset approaches. Its free option inside Daz Studio

If you couple that with a cloud cover product design for use with the sun sky option you can get some decent results of an ever changing sky.  You would need some kind of exterior environment directly outside the windows.  This is an example of one such product though I haven't used it  but the principle works.  https://www.daz3d.com/iray-sky-pro

FirstBastion

edit:  I really should read the comments before posting an answer,  I agree with  Hylas's comment above.  

daveso

if a background image was used, couldn;t one of the weather product overlays/planes be placed in between the image and subject window?

FSMCDesigns

Stay away from any interiors with large windows

Jason Galterio

You can add a Skydome to a scene with an HDRI. Modify the transparency of the Skydome to create an overly to change the weather. Won't change the position / make up of the clouds if they are present in the original HDRI.

Another option is to render twice. Once with the HDRI, a second time with what you want to weather to look like. You can layer the images and work with the blend styles to create the effect you want.

kyoto kid

...I have Iray Sky Pro and it works very nicely as the cloud dome can be rotated by itself to change the cloud view and still be correctly illuminated by the Iray Sun.

With straight photo backdrops you have to be careful to match the shadows cast by the Iray sun with the angle of those in the photo.  This can present issue when needing something in the background while the camera is viewing through windows of an interior setting. If using an HDRI, the best solution for adding ambient light inside the room space is a using a "softbox" light which is basically a primitive with the emission channel turned on that isn't seen by the camera as the room space will be in complete shadow from the ceiling plane.

If you want the sun to shine through the windows into the room space  it gets trickier. For example having a photo of a ridge of hills illuminated directly by the sun yet wanting the sunlight to stream through the windows facing those hills, could appear a bit incongruous.  This is one reason why I tend to build the foreground scenery details using geometry. 

 My main issue with using full HDRI's (besides them being someone else's photo environment), is sometimes luminosity and temperature of the "sun" is a bit off and the sun is usually in a "static" position (the IBL Skies sets by Denki Gaka  stand out as like the old LightDome Pro for 3DL, they include a range  of domes for each sky condition with the sun at different angles between zenith and the horizon)..

As to positioning the sun in Sun/Sky mode, I find using the Sun Dial rather than the default coordinate/time settings to be a much simpler way to set the sun to the desired elevation and azimuth (rotation).  This control can be found in the Content Library tab under Render Presets/Iray/Sun Dial Set.

Doc Acme

Daz really does have a spiffy Sun/Sky implemtation.

But if ya really want get silly with this:

https://www.lightmap.co.uk/

You can make/edit your own HRI's.  And then some.

WendyLuvsCatz

yeah even the animated texture scripts don't work on it, it would be nice if it at least rotated slowly if just clouds like Flowscape and a few other softwares do

I use animated skydomes in other softwares affecting lighting and it is awesome (I tend to shy away from HDR files though as they are humongous) if fact I render my 360 spherical image series in Carrara and iClone for them to save resources rather than having volumetric clouds in the former clogging my scenes.