Extracting textures from HDRI

[Metin_7]

Hi,

I've got a few latitude-longitude HDR textures I'd like to extract parts from to use as texture maps. But to be able to use them as texture maps I'll need to remove the spherical distortion from the images. Do you happen to know a (freeware) tool able to do this?

I've got Photoshop CS5, so once the distortion has been neutralized I can do the cropping with Photoshop. Or is it maybe even possible to remove the distortion using Photoshop CS5 as well?

Thanks in advance for your help.

[MoonDoggie]

Well since I don't know of any anti-spherize plugins. I would just attempt to do it manually, at least until you find a better solution.

[3DMK]

AHHHH Brainstorm

JUSt load up your HDRI in max and render out what parts you need.

In max you are loading your spherical map, but through a camera all distortion is gone and you should get a nice flat tex....well as flat as possible!

[Metin_7]

Thanks for your reply Colin. I wouldn't know where to start doing this manually.

3DMK, thank you too! Not a bad suggestion, I can try that. But can you also render to a HDRI from Max, keeping all exposure levels?

[plastic_]

you can also do that with ptgui.

[Metin_7]

Thanks Marc. I'll check out PTGUI as well.

[3DMK]

I think if your input gamma is 1.0 and your output is 1.0 and you save as 32 bit you should have an output exactly the same output as your input. [Make sure you uncheck 'affect background' in colour mapping.

Hope this helps

[Metin_7]

I checked out PTGui, but as far as I can read at the site only PTGui Pro (not freeware) can do advanced panoramic transformations. I also tried HDR Shop, but no luck as well.

Maybe I'm the first person in the world who wants to use (parts of) a panoramic HDR image as a conventional, non-distorted texture.

[Metin_7]

I think if your input gamma is 1.0 and your output is 1.0 and you save as 32 bit you should have an output exactly the same output as your input. [Make sure you uncheck 'affect background' in colour mapping.

Hope this helps

Thanks again, I'll try this!

[Metin_7]

I tried the V-Ray approach, but I can't get the desired environment part to be small enough to fit into one render and a bit of distortion remains there as well.

This seems to be harder to realize than I hoped.

[3DMK]

I tried the V-Ray approach, but I can't get the desired environment part to be small enough to fit into one render and a bit of distortion remains there as well.

This seems to be harder to realize than I hoped.

To get more of the image in render you will need to increase your FOV [what is your camera lens currently??}

You will always get some distortion as 360 degree panos are usually done with a very wide angle lens...around 10-18mm.

Hope this helps

[Metin_7]

Thanks again, I'll retry it.

[egz]

You could also use a box camera to unwrap the image to a format that is easier to work with in Photoshop.
Set up the camera like this:


Make sure your render has an image aspect of 0.75 (ie 1500x2000 px), and render. If you set the vertical resolution to something close to the width of the spherical image you shouldn't lose too much information.
You end up with with an image like this with six squares in a cross, each representing the view of the unwrapped HDRI along one axis:



You can also change the rotation values of the HDR, or rotate the camera, to change the box projection if you need to straighten certain lines etc.

[Metin_7]

Thanks a lot Torgeir! I already tried to convert the latitude/longitude to a cross type of HDRI, using HDR Shop, but the result was still distorted. I'll look into your suggestion, thanks again.

[STORM8_LLC]

Why don't you just map it to a sphere with Full self illumination and then bake a texture map?