HDRI Time-Lapse Sky Dome FAQ

HDRI TimeLapse FAQ

Q: What’s HDRI?

A: HDRI stands for High Dynamic Range Image, and when used as a background or environment in computer generated imagery, these images can be used to light your virtual scenes.

Q: What’s a time-lapse?

A: Film is usually shot at a frame rate of 30 frames per second or “real time”. In a time-lapse, frames are shot once a second, or once a minute. This results in the passage of time being greatly sped up.

Q: What’s a sky dome?

A: An image of the sky shot in hemispherical format – sometimes with a single 180 degree fisheye lens pointed straight up, sometimes shot using a special panoramic tripod head. These sky domes are then dropped into a virtual scene or are used to replace an existing, boring or unwanted sky in still photos or film.

Q: Will it work with my 3D software?

A: All software listed below has been confirmed able to load HDRI time-lapse sky image sequences. Please contact me if you’ve confirmed our time-lapse HDRI skies work with software not on this list.

  • V-Ray 3.0 / 3dsmax
  • V-Ray 2.0 (via Autodesk’s IFL manager)
  • Blender Cycles/Octane
  • Lightwave Octane
  • Modo 701+

Q: What’s all this business about un-clamped and 1-step HDRI lighting?

A: An unfortunate number of HDRIs you’ll find online are shot with just a few brackets (I call them MDRs or medium dynamic range), and don’t capture the true dynamic range in an environment. When you use images like this in your scene, you often have to fix them by adding in your own sun and making other adjustments. If you use an unclamped HDRI, you simply drop it in and your lighting is complete, accurate and realistic.

I wrote about this on CGArchitect and also did a video discussing it.

Q: The file sizes for these are crazy (40gb for the largest), are they usable?

A: Each frame is only ever loaded into memory one at a time, so it is exactly the same as using a single HDRI or background image. You will just need 40gb of HDD space. If you order on USB you can load the frames off that and keep your HDD space. If you are working over a network, or want to work with proxy footage, I’ve provided 1024px resolution frames with each time-lapse sky dome.

Q: How long will they take to download?

A: First, make sure you have no downloads running, second, go to www.speedtest.net, find your MBPS download speed, then go to www.numion.com/calculators/time.html, enter the size of the time-lapse you want (7-40gb), and it will tell you roughly how long it will take.

Q: Large downloads are painful, they usually drop out and I have to restart a million billion times ugghhhhh!

A: I’ve partnered with Continuata, who provide a super reliable, error tolerant solution. During download, you can yank your ethernet cable out, switch your modem on and off, pause and resume, power your computer on and off – and it will pick up where it left off.

Q: How much are they?

A: The shortest are $229 while the longest is $289 USD. USB/Shipping is $49. There is a bundle that contains all 5 time-lapse skies for about the price of 4, available for download or external HDD for +$99.

Q: Why are the download versions more expensive than USB?

A: This is to account for the expense of using the Continuata service and Amazon s3. The files are pretty massive and neither of these services are free. Regardless, once USB+Shipping is added to the USB version, download is still much cheaper.

Q: I want a time-lapse that runs for about N minutes, do you have any?

A: The longest runs for 50 seconds, and can be frame-blended (time-stretched) to almost any length, if you have the hard drive space. The motion speed of course will get slower and slower.

Q: What is frame blending?

A: The time-lapses can be lengthened by frame-blending (or equivalent time-stretching methods) in programs like After Effects. Using time remapping, time stretching and pixel motion, new EXR frames can be created in between each frame.

Currently AfternoonSlow01 is the best for this, and Afternoon2Night01 is also quite good, with some very minimal warping possible.

You may wish to consider frame blending LDR background frames to save on space, and using the full size or smaller HDRIs for the lighting. Or potentially even frame blending the end result render (your success with this will vary based on your scene/animation!).

Q: How do I use these in _______ 3D program?

A: Tutorials coming soon!

You’ll want to use high importance sampling, unbiased or brute force rendering techniques for these un-clamped HDRIs.

For VRay 2 users, grab the IFL manager here and that should point you in the right direction. http://docs.autodesk.com/3DSMAX/15/ENU/3ds-Max-Help/index.html?url=files/GUID-EB7F4F5B-6082-44A8-AD50-C401FA758ABA.htm,topicNumber=d30e522900

For VRay 3 users, Tim Back from ArchAngel Visual did this quick and easy tutorial.

Q: You shot these skies incorrectly, that’s why there’s flickering.

A: Flickering is often the result of incorrectly shot time-lapse footage, but not in this case. Usually flickering is caused when the aperture or shutter speed is set to automatic, or the aperture is set to a non wide-open setting (aperture blades don’t open and close the same amount each time).

The flickering effect in Hyperfocal’s time-lapses however is caused simply because in one frame, the sun is out, then in the next (say a minute later) it is behind cloud. When the frequency of clouds and shooting speed line up, you can have a series of frames that are bright/dark/bright which causes flickering.

Depending on your scene, the amount of open space, material usage, etc, it may or may not be an issue. Some people like the effect! Read which skies can be problematic, with a detailed breakdown on flickering here.

Q: Have you got a sky that has these features: ……..?

A: This is it for now, but I’d love to hear what you’d like to see in the future.

Q: Is Paul Debevec in any way affiliated with your work?

A: No. I merely studied his original research papers and used his time-lapse skies to compare against my own during development.

Q: What is the licensing type?

A: Royalty Free. Read the license here.