HDRI for Dummies

[Todd Dodd]

I am new to HDRi's and how they are used, manipulated, ect...  Does anyone know where I can get some good foundational training on how to use these in NXT?  Webinar, Tutorial, book, ect..  I am looking for indepth info beyond the quick "click here, click here and click here, and now you have an HDRi image in your rendering."  I have gotten an HDRi image into one of my renderings but it does not look right and I have no idea how to fix it.  Thanks for your help, Todd.

[Chas / Aug Posekany]

Isn't there some instruction on the Wiki pages?

I went and looked and there is some information there to get you started.

[Todd Dodd]

Yeah I have read those but I am looking for something a little more indepth than that.  Like I said I got one in my rendering fine by following the wiki but it does not look good at all.  The wiki does not really give you any insight as to what to do if it looks bad,  what you can adjust what you can't adjust.  For example I downloaded an HDRi from Accustudio and put it in my rendering.  The HDRI has the ground/horison sitting up so high that it makes my model look like its in a valley.  I have a grassy plain floating above the top of my building.  How do I get the horizon line of HDRi to match up with my model so that it appears to be on a more level site?  Is there any sort of Wiki or tutorial that cover more indepth items such as this?

[Chas / Aug Posekany]

I've always used the HDRI background for lighting effect. I then always remove the HDRI visible background either in the nxt editor or in photoshop and replace it with a background that fits the situation.

I have never relied on the HDRI to be the background in my final image.

Maybe we can both learn from someone elses input.

 

[akinlolu olugboji]

You take a suitable image background and convert to an HDRi with the NXT widget. Then use the  appropriate multiplier via intensity to get it to behave as close to reality as possible.

  http://www.accurender.com/photo/albums/country-villa-1

[Chas / Aug Posekany]

One big tool I find very helpful is using the lighting channels. You will note that your HDRI has a default channel.

Place you other lights on seperate logical channels then render and save you file as a .nxt image. You can then use the nxt image editor to adjust the HDRI channel up and down while using the overall brightness tone operator to equalize the image.

[Todd Dodd]

I read the wiki on channels, its not very clear, pretty brief, but I think I got it.  The initial image is looking better.  I was hoping tofind more of a step by step type of how to like they have doen for previous releases so that I have a base precedure to start from.  Anyway thanks for the help, I am sure I will have more questions as i try to wrap my head around this concept.

[Roy Hirshkowitz]

Post some examples here so people can actually help you instead of trying to imagine what "good and bad" look like.  Start with images.

 

To test an HDRI for lighting-- use the Studio preset, turn off any lights, select your HDRI,  and press the button.  Nothing more is required.

 

Not all HDRIs are created equal.  Getting a good map is more than half the battle.  Many of the ones on AccuStudio aren't really HDRIs, just converted backgrounds.  The horizon line of a correct, spherically projected HDRI, is supposed to be the equator-- if it's not there isn't anything you can do to adjust it.  The map is no good.

 

Check some of the other links on the hdri download page.  Four low-res HDRIs from Paul Debevec are included with nXt.  They're in the program folder.  These are normally not suitable for use as backgrounds-- but work fine for lighting.  For backgrounds you'll need to find some higher-res ones.

[Todd Dodd]

How do you access the NXT image Editor?  I have read the wiki and it says to use the: File / Open menu to load the image into the editor.  There is not a "File / Open" menu on the rendering window when the rendering is complete. The only menu's I have access to with out starting another program is the Autocad Architecture menu's and they do not provide access to the NXT Image editor.  I have checked my program list and I am not finding the NXT image editor there as a stand alone program either.  Do I need to download it seperately from the Accurender download?  Thanks for your help!!! 

[Roy Hirshkowitz]

It's a standalone.  You should have a folder in your Start menu called nXt, with access to a few standalone apps. including the Image Editor.  If not, let me know.

[Sean Casey]

If anyone would be so kind as to post images of renderings with HDRIs and without, this would be useful to make a comparison. I understanding the theory behind their use but would benefit from seeing actual samples which I can use to evaluate their benefits.

[Roy Hirshkowitz]

You can easily do it yourself (for exteriors anyway)-- just use the Studio lighting preset and compare it to the Exterior preset.  The default HDRI is a eucalyptus grove.  Three others (I think), are provided.