Help with environment map

[Bosseye]

Hi all, hows tricks?

Right then, I'm trying to get an environment map to work, so I've searched all I can find on the forums and I've seen the devs 'compositing' turorial but I'm still having an issue with the scale of the map:

1) I've downloaded a free .hdr map of a grassy landscape with trees.

HERE IT IS!



2) I've converted it to an .exr file
3) Loaded it in sketchup, is visible when rendered, rotates fine etc

BUT!

The scaling - at the moment the view of the env map is waaaaay too zoomed in, ie a wide open landscape with a huge field on one side and a large stand of trees on the other, when I render, the environment map is zoomed right in on one of the tree trunks and so is way too close, missing out on the actual landscape and is also too blurry to look any good.

SEE WHAT I MEAN! As you can see, the map in indigo is zoomed right in on the tree to the right under the sun flare...



Rotating makes no difference, obviously just rotates the map around, the width parameter doesn't seem to do anything whether I set this to 1 or 10,000, I've tried spherical and lat/long and as far as I can see theres no way to 'zoom out' or scale the env map?

I've tried shrinking the dimensions of the .exr file right down in photoshop but I get the same result just lower res I've tried increasing the dimensions of the image but this gives the same result but kills rendering times, I've tried upping the resolution of the image, but this ultimately just whacks the dimensions up and causes memory errors in Indigo.

Where am I going wrong?

Any clues? Cheers!

[Soup]

Yes you would think that resizing the map would scale it properly...
A bad hack could be resizing the image but keeping the canvas the same size... But, ew.

Try the image plane technique described in that tutorial, make it an emitter, and maybe use sun & sky as well..

[galinette]

I do not think the background is too scaled. It is the correct result if you consider the FOV of your camera settings.

Sketchup default has a FOV of 35°, which is a 35mm film equivalent of 60mm focal. Set this to 60° for instance and you will have a more eye-natural FOV.

Simple explanation : an envmap records the 360° spherical color of what is surrounding the camera, whatever its resolution is. Then indigo takes the camera FOV and orientation, and automatically creates a background corresponding exactly to what the camera will see of this environment. Normally, you cannot get wrong (if the envmap is not wrong) and always get the physically correct background from the envmap.

You can hack and use the backplane technique, but then you will get a hacked result (magnification of the background not really consistent with object size). But this may be what you want!

And last thing to consider : the objects in the envmap (trees) are supposed to be at infinite distance. That means, your scene size should be somewhat smaller than the real distance of these trees. If the trees are 20m away from the camera when recording the envmap, then scene objects should be not farther than 10m, otherwise something will look wrong and envmap objects (tree) will feel like "huge" objects.

All this is a little bit complicated to explain without a picture, but just remember these short hints:
- Set a larger FOV (such as 60-70° or 28-35mm) to have something that looks like eye vision with envmaps
- If you use an envmap, choose it so that objects in it are much farther than total scene size.


Etienne

[Ecifircas]

And is there a way to make your scene feel like it is "touching the ground" of the environement map?

[galinette]

Thats not really possible with indigo without a little bit of compositing with another software (like photoshop).

In non physical renderers, you can define a ground plane and apply a kind of "shadow matte" material on it. This special material will look transparent but will receive shadows.

In physical renderers you can't. These materials would be violating optic laws and would screw up the algorithms.

Try to render several passes:
- One normal pass like the picture you posted
- One "alpha mask" pass
- One pass with a grey plane for the shadows
Then composite all these to make the required effect with photoshop.

Note that, with your chrome teapot, you will not be able to have shadows on the teapot reflections. Also, if the teapot makes strong caustics, the result may be difficult to composite.

Etienne