? tutorials for using HDRI resources ? exr files?

Diomede

I was going through my 3D folders and noticed that I haven't been making use of hdr as much as I should.  In particular, I'm not sure I understand all the files that come with HDR packs.  

Is there a general walk through with the basics?

On a more expert level, is there something that goes through all the file types and adjustments?

Take for example, the Skies of Gaia pack for Iray.  https://www.daz3d.com/skies-of-gaia-volume-2--40-8k-hdris-for-iray

Instead of hdr files, I find exr files.  Can they be used?  Can the duf files be used in Carrara somehow?

WendyLuvsCatz

you need to convert exr to HDR or any other format for Carrara as it doesn't read them

however even converting it to a jpg Carrara can still use it as an ibl

its not fussy about format for image based lighting

Gimp will do it

Bunyip02

If you don't want to use GIMP there is also Picturenaut !

http://hdrlabs.com/picturenaut/

Dartanbeck

WendyLuvsCatz said:

you need to convert exr to HDR or any other format for Carrara as it doesn't read them

however even converting it to a jpg Carrara can still use it as an ibl

its not fussy about format for image based lighting

Gimp will do it

The HUGE main difference here is that HDR (incl EXR, etc.,) are in float32, meaning that they hold data beyond the rgb scale, which limits us from 0 to 255.

Using HDRI fro lighting, it's the values above 255 that produce illumination as if it was an actual light in your scene. In contrast, an image that is not float32 (Carrara only supports HDR for float32) will be using the same conditions as a normal background setting as a lighting aid - not exactly a true light source. This goes for other render engines as well. We can get lighting information from any image background, but float32 data has the ability to actually cast directional light.

I'm certainly no expert on this, but I did learn that as I began adventuring into making my own HDR images

Example:

In PhilW's Advanced Techniques for Carrara, Phil demonstrates how we can take multiple 'exposures' of render, and then merge them into an HDRI using Photoshop. Nowadays only the subscription version of PS allows us to do this, which was my main push toward Affinity Photo - buy it once kind of thing. Here's a cool video on how to merge multiple exposures into and HDRI using Affinity Photo (I love this instructor!!!)

When exporting as an HDRI, you'll be 'keeping' the extra data from all exposures, which Carrara (or other engine) can use for 'actual' illumination - reading the above 255 data as projected light. Something like that ;)

Dartanbeck

I intend to revisit all of this some day. In fact, it's actually one of the priorities but is below a whole pile of higher priorities! LOL

This was my first HDR test in Carrara.

Experiment

Use HDR as light source

Test HDRI as being the Only light source

Result - success, but revealed that I require a lot more experience with making the various 'exposures' as well as merging them to an HDRI. We are, however, seeing directional lighting - something that will Not occur from something that is not float32 (32 bit)

The problem that I had/have with this idea is that it takes so very long to render in this way. It requires full Global Illumination with Indirect Lighting, and only really benefits (I think) if those settings are turned up significantly - I could be wrong. This test only used meager settings in the render room. Like I say at the top, I will be revisiting this because I'm hoping to find a good workflow using this process.

Yeah, it's still dark, but it proves that the HDR casts directional lighting. The amount of light coming from the HDRI has more control in the Background tab than a non-HDR background.

If I remember correctly, this next one was my first Iray test - again using an HDRI that I merged myself.

I never really did put the time into figuring out how to best set up Iray for animation rendering. Even with my new machine, I'm not happy with the time it takes but that's without looking deeper - and I know there are tutorials on how to speed up the process. Another thing on my list of things to do - Argh!!!

The HDR I made for that one (above) was made using the low-polygon-count BG cityline from mmoir's BG Landscapes for Carrara. I populated an entire 360 degree scene using the buildings he gives us in that pack. They render really fast and still look really cool, I think.

Dartanbeck

So then I made a few HDRI using my EnvironKits - using different lighting techniques for getting the various exposures. That's the part that I still need a lot of experience with. I need to find a good workflow getting just the right lighting for each level - and get that down just right.

I did this one in Iray, but I did add a rim light to enhance the right side of him with the red/yellow lava color

The reason I was using Iray for these is because that's what I was doing at the time - experimenting with making HDR for Iray

Using HDR only (no other lights) in Iray

Using the same HDR only (no other lights) in Iray, but with a little embellishment on the lights on the ship using Howler's lens flare

Dartanbeck

Float32 (32 bit) images contain everything that was 'soaked up' when the image was taken. When we 'develop' the image, we're optimizing it to fill the full range of RGB from 0 (black) to 255 (white) and, as we see in James' excellent video tutorial above, enhance the tonal range in between. We're doing this using all of the data, but the developed result, the final file, the bmp, jpg, png, tiff, etc., is now, what... 8 bit? 16? Not remembering of hand. But it's condensed down to the RGB scale.

This is where we can easily see 'blow-out' in an over-exposed image, or unrealistic-looking pools of black in under-exposed images. 

Well float32 allows us to use the over and under exposed data as information about the 3d space around us and fill it with light, or suck it away - I think. 

I've tried experiments with just small orbs of light and niothing else. It was getting to the point where I wasn't getting any of my other work done, so this was when I aborted and put it off for another day.

Things to note from my experiments that I feel are very handy:

We don't need to 'see' the HDR - set something in backdrop to replace or remove (black) the background image - black backdrop allows render-to-alpha

In that case, the HDR sphere doesn't necessarily need to be HD - depending on the accuracy we're looking for

PhilW's Realism Rendering is a great resource!

PhilW's Advanced Techniques for Carrara is a great resource!!!

Diomede

Thanks, everyone.  Excellent info.

Diomede

Here is a quick test with an HDR in the JDA pack that has rural virginia.  https://www.daz3d.com/rural-virginia-hdri  Officially, it does not say that it is compatible with Carrara but it does say Iray.  I wanted to see if it could be used in C8.5.  The hdr file (not duf)  is found in the runtime\textures\\JDA HDRI\rural virginia directory.  All other light set to 0, including bulbs and scene ambient.  In render settings, sky light is checked on and gamma is set to 2.2.  Test object is a UFO in the DAZ store.

Dartanbeck

Yep! You got it! I buy HDRI packs from time to time to add to my collection, though I really don't use them - more just for testing and such.

There are some brightness options for you - better explained in detail in PhilW's Realism Rendering video course, but you have the brightness slider in the Background settings when Scene is selected and then you have the Sky Light settings in the render room. I've been away from this to remember which is best for which. One will do more to brighten the actual HDRI (I think this is the one in the Background settings) and the other plays more with how much light is cast by the HDRI onto the scene objects (I believe this is Sky Light in Render Room). 

Remember that it is Indirect Lighting that allows the HDRI to actually cast direction illumination, if I remember correctly.

Diomede

Thanks.  I don't have indirect light checked for the UFO test.  Always more to test.