focus range on when using HDRI

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focus range on when using HDRI

Postby alaman64 » Mon Feb 08, 2016 2:25 pm

alaman64 Mon Feb 08, 2016 2:25 pm
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.

2016-02-08_9-21-30.jpg
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Re: focus range on when using HDRI

Postby face_off » Mon Feb 08, 2016 8:55 pm

face_off Mon Feb 08, 2016 8:55 pm
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).

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Re: focus range on when using HDRI

Postby alaman64 » Mon Feb 08, 2016 9:27 pm

alaman64 Mon Feb 08, 2016 9:27 pm
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
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Re: focus range on when using HDRI

Postby linvanchene » Mon Feb 08, 2016 11:28 pm

linvanchene Mon Feb 08, 2016 11:28 pm
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.

- - -
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Re: focus range on when using HDRI

Postby face_off » Tue Feb 09, 2016 1:24 am

face_off Tue Feb 09, 2016 1:24 am
That's good info - thanks linvanchene.

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Re: focus range on when using HDRI

Postby alaman64 » Tue Feb 09, 2016 3:54 am

alaman64 Tue Feb 09, 2016 3:54 am
Thanks for the explanation,

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Re: focus range on when using HDRI

Postby alaman64 » Tue Feb 09, 2016 3:05 pm

alaman64 Tue Feb 09, 2016 3:05 pm
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?
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Re: focus range on when using HDRI

Postby linvanchene » Tue Feb 09, 2016 6:27 pm

linvanchene Tue Feb 09, 2016 6:27 pm
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.jpg
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.jpg
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...

- - -
Attachments
Dome test files v1003.zip
zip with dome .obj and .ztl v1003
(342.52 KiB) Downloaded 235 times
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Re: focus range on when using HDRI

Postby alaman64 » Wed Feb 10, 2016 4:19 pm

alaman64 Wed Feb 10, 2016 4:19 pm
Thanks linvanchene for taking the time to try it,

I'll download you're sphere and see if I can figure something out.

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Re: focus range on when using HDRI

Postby DrHemulen » Thu Feb 11, 2016 10:44 am

DrHemulen Thu Feb 11, 2016 10:44 am
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
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