About HDRIs and matching backplates

Discuss Simlab Composer released by Simlab Soft
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numbthumb
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Joined: Tue Aug 31, 2010 1:27 pm

About HDRIs and matching backplates

Postby numbthumb » Fri Sep 10, 2010 11:04 pm

Hi everyone!
I apologize if the question I'm asking has already been answered, but I would really appreciate if someone could give me some clarifications about this one.
I have stumbled upon some HDRIs with "matching backplates" on http://www.doschdesign.com/products/hdri/. Now, as far as I know ( and I don´t really know much ) a backplate image is a photo into which a model is placed, and then HDRI would be used for environmental lightning and reflection.
But what exactly would be ment by "matching backplates"? A photo taken at the exactly same place, matching the aspect, the resolution, or something else? In other words, is it a prerequisite for realistic rendering to always use such sets ( HDRI plus respective backplates ) ?
Pardon me for being stupid and thanks in advance!

SimLab
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Joined: Mon Jan 04, 2010 8:09 am

Re: About HDRIs and matching backplates

Postby SimLab » Sat Sep 11, 2010 9:59 am

This is not a stupid question at all, HDR as you described is the spherical environment from which the model gets the lights.
When placing a car for example in the environment, it will fill part of the created image, while there will be some background part not filled by it.

The user can select one of the following 3 options to fill the background:
  • 1- From environment HDR: in this case the same environment spherical image will be used to fill the background
  • 2- Single Color: the user selects a single color to fill the background
  • 3- Image (Back plate): usually the environment (HDR) represents a large sphere, so the resolution when used to fill the background is low, this can be fixed by using backplates, which are high resolution 2D images of the same scene, to be used to fill the background of the image.

So Backplate is not a prerequisite, but it can help in improving the quality of the output image

Cheers,

Ashraf

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numbthumb
Posts: 11
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Re: About HDRIs and matching backplates

Postby numbthumb » Sat Sep 11, 2010 10:20 am

Thanks a lot, Ashraf, I was really confused about that.
Cheers!

dantas
Posts: 228
Joined: Thu Apr 08, 2010 10:56 am
Location: Australia

Re: About HDRIs and matching backplates

Postby dantas » Sat Sep 11, 2010 4:44 pm

Hi numbthumb, just to add to this, the actual rendering community or someone with a good eye for detail will pick up that the reflections on your model from the environment(HDR) are not matching the scene(backplate) if they were not matched, so your render will look more realistic if you have matching backplates, but to the untrained eye of the general public it wouldn't really be picked up, the render would be perceived as a real photograph, unless you had a sunset HDR with a midday snow scene backplate, then it would look odd to anyone.

Cheers
~Danny~

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numbthumb
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Re: About HDRIs and matching backplates

Postby numbthumb » Sat Sep 11, 2010 6:00 pm

Thanks for the explanation, Danny !


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