Tweaking an EXR image.

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pauljohns
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Tweaking an EXR image.

Post by pauljohns » Fri May 16, 2008 3:09 am

Hi everyone!

Below is my first attempt at using an HDRI image to give off cool reflections and stuff. I'm pretty happy with the results, since I'm a n00b and this looks a bit better than my usual renders, but I was wondering how I would go about tweaking a couple of things about the HDR image:
  • Although I am using DOF, and background is and should be blurry, I can also tell that it looks kinda low-res. Like maybe it got stretched out too much or something. Would I change that with world scale?
  • The bottom of all of the HDR images I have seen have a black bottom on them. How Can I move my image down a little to where the black line doesn't appear in my image?
Thanks for all of your help in advance, everyone!
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2492860469_d55f14a7cf_o.png
My first attempts at using HDRI (EXR) and DOF.
2492860469_d55f14a7cf_o.png (536.17 KiB) Viewed 2875 times

BbB
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Post by BbB » Fri May 16, 2008 3:14 am

Generally speaking, I would not use and HDR map as background. Use them only for reflection. Even the most hi-res of images tend to look crap as backgrounds because they're blown up so much.
You can try to find a jpg, flat version of your HDR map and use this as background - either projected on a plane placed behind your object, or in post using an alpha channel render as a mask.

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pauljohns
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Post by pauljohns » Fri May 16, 2008 3:19 am

oh, ok, gotcha. So most of the time, I'll either be using a texture mapped plane, or an actual rendered background. Cool, thanks! Now I know! That also answers the black line thing! Thanks BbB!

juce
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Re: Tweaking an EXR image.

Post by juce » Wed Jan 19, 2011 9:32 pm

Bertrand,

First of all, your "GH House Interior" on Ronen Bekerman is stunning. Nice to have something to aspire to. Everyone should check it out: http://www.ronenbekerman.com/challenges ... e/winners/.

I wonder if you could answer a question for me? You suggested that pauljohns use an image plane or an alpha channel as a backdrop for his render to work around the blurry HDR problem. If he were to do this, what should the light source be?

Experimenting a little I found that the lighting achieved by using 'sun and sky' or 'sketchup background color' looks out-of-place in relation to my image plane. I much prefer the versatility of using an HDR to light my scene but the blurriness and 'zooming in' are a source of frustration.

Any suggestions you could offer would be greatly appreciated

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galinette
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Re:

Post by galinette » Thu Jan 20, 2011 8:15 am

BbB wrote:Generally speaking, I would not use and HDR map as background. Use them only for reflection. Even the most hi-res of images tend to look crap as backgrounds because they're blown up so much.
I'm rendering 1920x1080 images with HDR envmap as background, and it looks sharp! You just need a very high resolution envmap. Best is to do it yourself with a SLR, but some very high res images can be found on the internet.

For instance, if you make outdoor animations or stereo images (like I do) , there is virtually no other choice than using the envmap background, because good parallax is almost impossible to match by compositing, and it looks fake.

Etienne
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http://www.eclat-digital.com

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ENSLAVER
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Re: Tweaking an EXR image.

Post by ENSLAVER » Thu Jan 20, 2011 1:06 pm

Yeah you can use HDR images for backgrounds in some circumstances, you do really need very high res images given they cover 360° - Over 10k pixels wide should be reasonable... with a bit of dof.

Try this site, they are pretty much all 10,000 x 4,000 - http://www.openfootage.net/?cat=15

Still, best practice would be to find hdrs with backplates. You can use a lot lower res which is good for ram(10k maps can use 1gb+) and indigo setup times. It's just hard to find free hdri's that come with backplates. There are a few sites that sell them though.

Soup
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Re: Tweaking an EXR image.

Post by Soup » Wed Jan 26, 2011 10:33 am

*ahem* This thread is 3 years old, and BbB hasn't been active here for a while now - he might not get the message 8)

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ENSLAVER
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Re: Tweaking an EXR image.

Post by ENSLAVER » Thu Jan 27, 2011 4:32 pm

You never know :lol:

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