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Scaling your environment/HDRI???


Tim Saunders
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I am a huge fan of the fill light effect you get when using HDRIs in exteriors. However the problem I faced when I was working on Challenge #2 for AVC2006 was when I rendered the scene positioning my spherical environment with an hdri was that the background was extremely stretched out and pixilated. I have one of the hdri collections from dosch and great they may be at giving me the reflection and environment light I'm looking for, there is no way I can get the background I want. I have the same problem with any spherical invironment.

 

So now my question... Is there a way to scale down the size of my environment sphere so it is not so stretched out? I'm not looking for a way to fake it by rendering the scene with a background alpha channel to be replaced in photoshop. That is my normal technique, but I would like to know if there is a way to make the reflection, environment map, background to match accurately, while still giving the desred background.

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your spherical map should be of a huge resolution to show up well in the background. imagine you render 2500x2000 pixel, you will only see a small part of the entire enviroment, depending on your FOV. as the spherical enviroment covers the whole 360° it should be many times your output resolution, let's say 10000x5000, it is nearly impossible to get spherical backgrounds like this, although i saw some collections like that, but these were not HDRI, because it is nearly impossible to shoot a whole 360° panorama in a short time, consisting of several images, and several exposures.

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My point exactly. If my spherical environments are aproximately 2500 pixels wide, and even if I only render at 2500 pixels wide the background is extremely stretched out sinse I am only seeing maybe 25% of the map. the remaining 1875 pixels ar stretched on the non-visible parts of the scene. I see no way around this other than replacing the background post rendered.

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Applying a large panorama map ( 6000 X 3000 pixels) to the inside of a sphere in Houdini, works great. It renders super crisp with no pixelation at ~640 X 480 (Apprentice version doesn't allow for a higher res.) There is some panoramic distortion, so applying a six-faceted cross shaped map to a cube (like QT panorama format) might give better results.

Doesn't really solve your problem in 3ds max, but just for your information :)

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  • 9 months later...

A physical background rig is the best way as i see it and it's what i use on every single one of my projects. Even when i want to use the hdri as the background i would never do it any other way because no other way gives you the kind of control that a physical rig gives you.

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If by rig you mean make a dome and manipulate it, and then applying your HDRI as a bitmap to it for a background, then I've done that but tried to use an HDRI as an enviroment with it and the environment doesn't show through the dome correctly...even with a normal modifier applied to it.

 

If that's what you mean. If that's not what you mean then I don't know how to rig. If it is, I still couldn't get to work right. Any suggestions?

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This is the rig that i was talking about. You just need to make sure that you have the rig invisible to GI, not cast shadows, and not visible by the dome light or any other lights you're using to illuminate the scene. The rig should be illuminate by a single omni light only, which shouldnt affect any other objects.

 

http://cgarchitect.com/upclose/VI/Week13/A_Little_Background_Information.pdf

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  • 4 years later...

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