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focus range on when using HDRI
Posted: Mon Feb 08, 2016 2:25 pm
by alaman64
Hi,
When I use an HDRI background and a plane as a shadow cathcher, can't figure out how to get the camera to keep the near background in focus and blur the stuff in the back ground. In iray it's simple i choose infinite sphere with ground and it works, can i do the same in octane?
here's a sample render from iray, notice how the ground under the box is in focus and stuff in the distance is blurry.
Re: focus range on when using HDRI
Posted: Mon Feb 08, 2016 8:55 pm
by face_off
Reducing the Thinlens->Aperture will increase the depth of field. If using an IBL, all parts of the IBL will get the same DOF effect (which will be the same behavior as iRay).
Paul
Re: focus range on when using HDRI
Posted: Mon Feb 08, 2016 9:27 pm
by alaman64
Hi Paul,
Sorry don;t understand, how do you change the thin lens aperture? is that the same as the regular aperture, if so, yes I know how to change that, and I do see the change in DOF, as you mentioned the backdrop is always out of focus, in Iray it looks like it wraps the background and create a ground object, so then things in the distance are blurry and things up close are in focus. maybe this example is more obvious
Re: focus range on when using HDRI
Posted: Mon Feb 08, 2016 11:28 pm
by linvanchene
face_off wrote:Reducing the Thinlens->Aperture will increase the depth of field. If using an IBL, all parts of the IBL will get the same DOF effect (which will be the same behavior as iRay).
Paul
alaman64 wrote:Hi Paul,
Sorry don;t understand, how do you change the thin lens aperture? is that the same as the regular aperture, if so, yes I know how to change that, and I do see the change in DOF, as you mentioned the backdrop is always out of focus, in Iray it looks like it wraps the background and create a ground object, so then things in the distance are blurry and things up close are in focus. maybe this example is more obvious
iiray.png
OctaneRender:
- the HDR background is a 360 degree sphere
- there is no way to indicate the distance between background sphere and camera
- there is by default no ground
Iray
- the HDR background is a dome
- you are able to indicate the distance to the background
- there is a ground
- - -
Background:
- the background part of the HDRI may be blurred the same way in both Iray and OR
not yet tested:
- in Iray the HDRI background depth of field may be calculated based on the indicated distance settings.
Floor:
because the Iray dome has
distance settings
a ground floor
depth of field may be applied to the floor part of the HDRI dome in Iray based on realistic calculations.
- - -
Re: focus range on when using HDRI
Posted: Tue Feb 09, 2016 1:24 am
by face_off
That's good info - thanks linvanchene.
Paul
Re: focus range on when using HDRI
Posted: Tue Feb 09, 2016 3:54 am
by alaman64
Thanks for the explanation,
Nick
Re: focus range on when using HDRI
Posted: Tue Feb 09, 2016 3:05 pm
by alaman64
So how can i get this done?
If i have a dome or half a dome that has floor and sky, would i be able to apply and HDRI texture to the dome and light the scene that way? I do remember seeing blackbody texture emission, do you think that would work?
Re: focus range on when using HDRI
Posted: Tue Feb 09, 2016 6:27 pm
by linvanchene
update / edit:
added more findings and updated the .zip file with some more dome .obj test files with flipped V and a spherical UV
alaman64 wrote:So how can i get this done?
If i have a dome or half a dome that has floor and sky, would i be able to apply and HDRI texture to the dome and light the scene that way? I do remember seeing blackbody texture emission, do you think that would work?
Which HDR image from which product are you using?
- - -
I did some tests but was so far not able to figure out a solution how to use a HDR image set up for a sphere to use on a dome with ground plane.
There was always distortion on the ground.

- dome flipped normals and flipped V
@ blackbody emission
If you are familiar with adjusting the proper power settings for the HDRI environment you can use a similar workflow to find the optimal settings for texture emission.
Using the HDRI environment seems much more intuitive though. I am still having issues finding the right balance of values when using texture emission with sky spheres or domes...
@ UV issues
It seems you have to use a dome with inverted normal facing inwards to see the texture.
You may also need to flip the V coordinate before exporting the dome from Zbrush to DAZ Studio.
I tried with experimenting with the following values
- the UV settings in Zbrush
- the "projection mode" in OctaneRender

- Which UV settings for a dome to use a sphere UV without ground distortion
Nevertheless I was not able to find a combination so it is possible to use a map that was created for a spherical UV and apply it to a dome with ground plane without getting the ground area distorted.
- - -
If someone wants to keep trying the updated .zip with a WIP dome .obj and two .ztl is added...
- - -
Re: focus range on when using HDRI
Posted: Wed Feb 10, 2016 4:19 pm
by alaman64
Thanks linvanchene for taking the time to try it,
I'll download you're sphere and see if I can figure something out.
Nick
Re: focus range on when using HDRI
Posted: Thu Feb 11, 2016 10:44 am
by DrHemulen
I think it's going to be hard without doing projection math of some kind.
If I undestand corretly, you need to show half of a spherial image on a plane. Maybe we could use methods from map making, there are several methods for such projections. I guess it should be possible to create a UV map that's based on such a projection?
With regards to the emission, remember that you can just use the "no shadows" trick on the environment sphere, and have a normal HDRI background shine through it.
Edit: Some inspiration maybe:
http://blender.stackexchange.com/questi ... here-shape