HDRI Lighting

[cberg]

I have a fundamental question about how HDRI background images work in Vectorworks.  In other programs, adjusting the brightness of the HDRI controls the amount of light that enters a rendering.

 

In the attached file, I have imported a simple interior HDRI into a scene.  It's pretty high res (as I thought these needed to be).  For clarity, I have turned the background on to understand where the light is coming from.  I have turned ambient light to zero.  And disabled indirect lighting.    I am finding that no matter what I do to try to control the amount of light coming out of the hdri image, the rendering appears to be the same.   What am I doing wrong?

 

Link to file:  https://www.dropbox.com/s/f4droj6tbdyqtok/Test.vwx?dl=0

 

[PVA - Admin]

This has happened to me a few times. So far, the main reason seems to be that if I didn't use a REAL HDR image for the panoramic background, then I couldn't control the brightness, nor was the lighting accurate, it was sort of an average color lighting of all the various elements in the image. I have noticed even stranger results on occasion, like renders becoming incredibly green or yellow because not all HDR information was present in the source image file used for a background I created. 

Example attached here of a confirmed working HDR image background with two brightness controls, I also used 2 separate render styles and bgs on this one for the comparison and added a light that I turned off in order to disable default lighting to make the difference very clear:

 

EDIT The attached background is REALLY high res, apologies for the huge file size.

Test_with_RWstyles.vwx

[cberg]

That makes sense.   I was wondering if there was something inherent in the HDRI image which was downloaded from a third party site.  Is there any way of figuring out whether an image is a real HDRI?

[rDesign]

@JimW - do the recommendations by @Dave Donley over at this 'FREE HDRI Images' thread still hold true, in that you should use "low res HDR for environment lighting and the high res for visible background" ?

Edited May 31, 2018 by rDesign

[PVA - Admin]

16 minutes ago, rDesign said:

@JimW - do the recommendations by @Dave Donley over at this 'FREE HDRI Images' thread still hold true, in that you should use "low res HDR for environment lighting and the high res for visible background" ?

I would say that is still true, but that you would now HAVE to use the .HDR files for any of these if you wanted to use them for lighting. I downloaded a handful and most seemed to include two .HDR files, one with a 2k or 4k in the name, and one with ENV (environment) in the name. These still work fine for me here, but the JPEG ones which some users might assume were what they should use because Explorer or Preview showed the image contained within (not always true with HDR format unless you have an app that reads them installed) and showed a dummy icon for the HDRs.

If you were using them just for appearance or reflection and not lighting, pretty much any image will work as a pano background, but for Environment Lighting specifically there are more rules.

[PVA - Admin]

22 minutes ago, cberg said:

That makes sense.   I was wondering if there was something inherent in the HDRI image which was downloaded from a third party site.  Is there any way of figuring out whether an image is a real HDRI?

Not sure, I had looked into this before but hadn't found a quick way. Generally if there is an actual ".HDR" extension, it's fine, but if its just a PNG or JPEG its no good.

However, it IS possible to just rename a JPEG to HDR and then it would look fine but not light properly, honestly I often just test them in a render before i trust them. This was part of the reason I didn't push for that big pack of backgrounds Luis and I made to be default content, it needed to be double checked for things like this.

[rDesign]

34 minutes ago, JimW said:

I would say that is still true, but that you would now HAVE to use the .HDR files for any of these if you wanted to use them for lighting. [...] These still work fine for me here, but the JPEG ones which some users might assume were what they should use because Explorer or Preview showed the image contained within [...].

If you were using them just for appearance or reflection and not lighting, pretty much any image will work as a pano background, but for Environment Lighting specifically there are more rules. The help file is a little vague.

 

Not to hijack this thread, but the page on Creating Panoramic Backgrounds in the Vw Help File should be more clear in stating that .JPG files are typically not HDRI files and cannot effectively used for HDRI-based Environment Lighting. 

 

25 minutes ago, JimW said:

Not sure, I had looked into this before but hadn't found a quick way. Generally if there is an actual ".HDR" extension, it's fine, but if its just a PNG or JPEG its no good.

However, it IS possible to just rename a JPEG to HDR and then it would look fine but not light properly, honestly I often just test them in a render before i trust them. This was part of the reason I didn't push for that big pack of backgrounds Luis and I made to be default content, it needed to be double checked for things like this.

 

While it might be *possible* to rename a .JPG to .HDR, this will not convert it to an HDRI file. 

 

How to tell — if you open the subject HDRI image file using a text editor like macOS TextEdit or Windows WordPad, the first few lines in the header will tell you if it is an HDRI file or not.

 

Example file header from an .HDR file that I downloaded off the net:

Quote

#?RGBE
FORMAT=32-bit_rle_rgbe

-Y 1500 +X 3000

[...]

 

Example file header from an .HDR file that I created in Cinema4D:

Quote

#?RADIANCE
GAMMA=1
EXPOSURE=1
SOFTWARE=CINEMA_4D
FORMAT=32-bit_rle_rgbe

[...]

 

The line in the header that says 'FORMAT=32-bit_rle_rgbe' identifies it as an HDRI file.

Edited May 31, 2018 by rDesign

[PVA - Admin]

1 minute ago, rDesign said:

While it might be *possible* to rename a .JPG to .HDR, this will not convert it to an HDRI file. 

 

Apologies, I don't mean to suggest doing it since it wouldn't work properly, just that you might find resources online where that was done. Didn't make that clear, my fault.

[PVA - Admin]

2 minutes ago, rDesign said:

Not to hijack this thread, but the page on Creating Panoramic Backgrounds in the Vw Help File should be more clear in stating that .JPG files are typically not HDRI files and cannot effectively used for HDRI-based Environment Lighting.

Actually, I think it needs to be split up even further than that. The IMAGE background will work just fine from anything, its only when the Environment Lighting is using a non-HDR that bad or confusing things start to happen. It references Lighting Options as another area that explains it, but its never spelled out. I'll reach out to tech pubs and see what we can do to make it clearer. 

Honestly I've been wanting to do this with a lot of the Renderworks help materials, integrating new things I learned/rediscovered in my content creation work.

[cberg]

Your file was helpful, Jim!  Doing some more testing, there was something odd about that HDRI file that I first experimented with.  When I tested another HDRI image, it worked fine.  As long as I know the process is sound, I can experiment with various environments to see how they affect my model. 

[zoomer]

I think there are available 2 types of HDR(I) images.

The "cheaper*" ones that work more or less like a high res Panorama photo,

where in Modo you have to adjust a brightness value manually,

and the better ones, real HDRI images that have correct brightness (+range)

information included.

I think these can't be easily created by hobbyists and panoramic Apps.

 

*Although many amateur photographers create such by shooting silver spheres

and sell these.

(Which is great btw)

 

Perhaps the ones without proper information unsettle VW.

Edited June 1, 2018 by zoomer

[grant_PD]

It should be fairly straightforward to see if an image is actually 32 bit

If you open the image in photoshop, a true HDR image will be 32 bit, and photoshop will tell you that when you look at the bit depth. 

If the image was just a panorama saved as 32 bit, you will be able to tell when you change the bit depth in photoshop, a dialog box will appear in which you can set the exposure and gamma.  You should be able to see a wider range of exposures available with an image that still retains (useful) 32 bits of information.  

[cberg]

Grant_PD and rDesign,

 

 

Believe it or not, the original HDRI that I used for my sample would have met both of those criteria, but still didn't work in VW.  That's fine; I wasn't super invested in using it.  I am leaning towards Zoomer's explanation because, upon closer examination,  the interior studio scene does have a DIY look-feel to it. 

 

Mostly I was wondering whether I was understanding the software functionality as designed.  You all are awesome!

Edited June 1, 2018 by cberg