[casey]

I'm wondering how to do this.

Occasionally I have scenes in the real world, and I would like to be able to place objects into them such that Maxwell renders the lighting correctly for the object so that when composited, it looks real.

I read a good tutorial on the forums about rendering with a grid, then placing an image on the grid so it lined up with the rendering properly. But unfortunately this technique doesn't really help with the _rest_ of the lighting, which is the full sphere of irradiance.

So basically, if I have a camera and a tripod, and I want to capture the lighting environment and put it into Maxwell, how is this done? I tried taking lots of photographs by spinning the camera around for good coverage, but I couldn't find a reliable way to turn these into an _accurate_ lat/long map for Maxwell to use. When I tried manually stitching them together, I found that the resulting renders didn't seem to have the lights/reflections coming from the right places accurately at all

- Casey

[Mattia Sullini]

It's easier than you might think
First take several shots of the same view with different exposure settings (check exposure bracketing http://en.wikipedia.org/wiki/Bracketing).
The more you take and the wider is the stop range, the better will be the hdr, but 3 shots is the minimum to get an almost working hdr.
Then you should load the shots both in photoshop or in a dedicated app (such as hdr shop) and build the hdr, and you are done.
More complicated if you need a panorama or an environmental mapping...in that case you can either get have a dedicated cameras (for just a couple of tenth of thousands dollars) or go for the software solution by manually or automatically merging the several hdrs you created into a complete 360° panorama.
Anyway the core concept lies in the bracketing: once nailed it the rest maybe will take some time but is more banal.
Not a step by step tutorial, but just an hint i hope could be useful for you

[casey]

I am not talking about the process of taking an individual photo. I understand how to capture an HDR photo.

The problem is the mapping of photos to an accurate lat/long map that Maxwell can use. Lat/long maps are particularly difficult to work with, unlike, say, cube maps ("cross maps") where the positioning is much more intuitive for manual editing.

I think it's pretty much a requirement that you need to use special software to make a lat/long map, because I can't see how else you could make an _accurate_ lighting environment without it. But I'm not sure what software actually makes lat/long maps, which is why I'm posting here. What are people using for this? Has anyone out there actually made a lat/long map of a real scene for use with Maxwell? What did you do?

- Casey

[Hervé]

The best at my taste.. so fast... so precise..

http://www.ptgui.com/

h.

... and if cash is not a problem.

http://www.spheron.com/

[Mattia Sullini]

Sorry if i understimated your skills
Maybe this link could be useful
http://www.panoguide.com/howto/panoramas/spherical.jsp

[martgreg]

Could you please show me the grid method you mention...this is something that i may find interesting...

sorry I cant help you ....but maybe you can help me

[casey]

http://www.ptgui.com/

That is pretty sweet. Which one of the projection modes is Maxwell's, I wonder? There's several options... Rectilinear? Someone should post a tutorial on this. Maybe that someone will have to be me, once I figure it out

Could you please show me the grid method you mention...this is something that i may find interesting...

Here is the original thread.

Basically, it doesn't help you with the lighting at all. What it helps with is composites where you need the background image to be aligned properly. But it's a nice trick.

- Casey

[Burnum]

PTGui Pro is the tool I'm using, it's based on some free tools but it's so much nicer to work with.

panotools has some info on the free stuff.

As far as shooting the Pano source images You need a Pano rig to make things work best, it's very hard to stitch images that have paralx issues.
If budget is an issue you can get a usable one like the Panosaurus. There are many nicer ones out there, but they cost a lot more. I'm fond of the Nodal Ninja myself


Mmmmm, spheron.... drool....

[Mihai]

You need to create a spherical panorama for use in Maxwell (360x180°)
I have an older Nodal Ninja pano head, a bit flaky but works ok. It's pretty important to avoid parallax issues otherwise the stitching will be difficult. Depending on the focal length of the lens (take into account the real focal length based on sensor size), you need to take the right number of overlapping photos for easier stiching, about 30-40% overlap. For a 12mm lens (19mm equivalent on a 1.6 crop factor sensor), I think I needed 8 positions for the middle row, 6 for the the bottom row, 6 for the top row, plus top and bottom.

[casey]

Wise words as always, Mihai... many thanks!

- Casey

[Burnum]

8 shots for the center Row before multiplying by however many other exposures you take? nice.

I currently have the cash to get a nice wide lens, so i've been using a 24(x1.6). It takes 222 shots to make an HDR... (bracketed by 3)
I'm currently looking for a way to hack my EOS 350D, so I can get more than 3 bracket steps.

I think they also call the type of Spherical needed a Equirectangular projection.

[Mihai]

On a sunny day you really need at least 6 exposures. The darkest one should capture the sun as small as possible. Even more than 6 would be better. 3 will not make a very HDR image, especially if you have the sun in the photo. It's very annoying for me too because the Canon 400D can only bracket 3 exposures, and I have to manually go and change the shutterspeed on the camera for each position. It would be easier with the Canon remote control but it's expensive, just to use it for this....

[Burnum]

do you have a way to calculate the changes in shutter speed? I have not tried to figure that out yet.
I also seem to be doing more indoor type than outdoor, so I don't have a Sun to deal with very often.

I use my Mac Laptop to take the shots, in the Image Capture application. It gives me a full screen view and I just hit the space bar for each. though I have been considering trying to figure out the best way to make 2 bracketing start points (so I only need to change the shutter twice) or hack the firmware to give me as many as I want. (there is the CHDK hacks for smaller canon cameras, but that doesn't work on an EOS)

I saw a list of all canon cameras on the web that shows how many they let you bracket. All of them do only 3, unless you get a 1D... Here is the list

Oh, I'm not sure yet if it's possible, but I think there may be a way to get Lightroom to talk to the EOS as well. I'll have to investigate further.

[Mihai]

I just go by one fstop difference, so I either multiply or divide by 2 the shutter speed for each shot. Maybe it would ok to go by 2 fstops difference and thus capture a wider range with the same amount of shots....anyone knows?

[Burnum]

the last auto bracket I did, was a 2 stop, it chose: 1/15, 1/60, 1/250
Hmm I didn't make the connection that it is roughly close to X4. I need to read up and or test, to see if you get clearly better results with 1 step vs 2 steps. (plausible)