Exporting a skydome for UDK

laskey_c5511810f5

Hi,

I’ve been messing with Bryce 7 pro for about a month. I like if very much. I want to use it for custom skies in the UDK. I am stuck, so I came here with a couple of questions.
I am having a hell of a time predicting what the export from the IBL tab is going to look like. Can someone explain the difference between the spherical and light probe export options. Also, does the file type influence the output?

Basically, if I position the sun at altitude 2 I would expect to see the sun at the edge of a circular 2048x2048 map of the sky, if I exported a spherical map. But thats not the case, the spherical map outputs a rectangular map.

If I output a ligh probe map, i seem to get the round image im looking for but he sun is much closer to the center of the circular map then it should if i want to project this map onto a semishere. And the edges of the circular portion and really stretched.

Thanks for any help and i continue to read and try new things.

Cheers,

Dave Savage

There may be a better more relevant video to watch but this one springs to mind being a recent one.
It may help you to watch it from the 5 minute and 30 second mark as it goes through the process of exporting from the Sky Lab.
it's for a slightly different end use but in reality is doing basically the same job as a skydome.

The rectangle one is correct. It will be 2:1 in proportion and will stretch the image so that when it's mapped onto a sphere (using a spherical mapping mode) it will correct itself rather like the standard image of the Earth we see reproduced in a flat form for atlases etc.)

David Brinnen

laskey said:

Hi,

I’ve been messing with Bryce 7 pro for about a month. I like if very much. I want to use it for custom skies in the UDK. I am stuck, so I came here with a couple of questions.
I am having a hell of a time predicting what the export from the IBL tab is going to look like. Can someone explain the difference between the spherical and light probe export options. Also, does the file type influence the output?

Basically, if I position the sun at altitude 2 I would expect to see the sun at the edge of a circular 2048x2048 map of the sky, if I exported a spherical map. But thats not the case, the spherical map outputs a rectangular map.

If I output a ligh probe map, i seem to get the round image im looking for but he sun is much closer to the center of the circular map then it should if i want to project this map onto a semishere. And the edges of the circular portion and really stretched.

Thanks for any help and i continue to read and try new things.

Cheers,

Can you tell us what format UDK accepts for skydomes? By which I mean, file types and projection method for the image. Knowing that would really help unravel how best to get you what you need from Bryce.

Horo

@laskey - instead of using the skydome only, use the full sky. Export as Radiance.hdr 96 bit and spherical. Then, in a HDRI-compatible graphics application, set the lower half to black if it disturbs you to have light from the undersife. A spherical panorama to be wrapped spherical on a sphere must have the aspect ratio of 2:1 (width:height). If you program only accepts domes, the aspect ratio should be 4:1. In any case, Bryce will output spherical as 2:1. Here's an example - tone-mapped, of course. Sun at 0° azimuth and 2° elevation.

laskey_c5511810f5

The tutorial im trying to follow is here:

http://www.youtube.com/watch?v=qU0hdaFARQo

I guess I need output as shown at 1:11 but Im hoping bryce can directly output similar to 3:01 so I don't have to manipulate it in photoshop. Or, how can I map the original image (1:11) to a dome?

Thanks

Horo

Why 1:11? I watched the video and the guy had a 4:1 panorama, which is half a spherical one. If he added the same size below with a black image, he'd got a true spherical map, which he could map on a sphere, then remove the lower half of the sphere. Transforming a half spherical panorama into a square aspect ratio and then transform it again as polar map for a dome is very laborious. Any dome has an aspect ratio of 4:1 if it is to be mapped on a half sphere (dome) spherical. If it's possible in the application you use to map polar, than you can take a photograph that was taken with a circular fisheye lens, looking straight up.

EDIT TO ADD: if you don't mind a bit of distortion, you can create a sphere in Bryce and make it full reflective (mirror ball). Then move the camera above the sphere and point it down. Set the aspect ratio of the document square (1:1) and move the camera until the sphere fills the document. This will give you a dome.