What is HDRI and how do I use it?
thistledownsname
Posts: 1,318
in New Users
I've seen it mentioned around, and seen links on places to get it, but I don't recal seeing it in the tutorials that came with DAZ.
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HDRI stands for High Dynamic Range Imaging and is not specvific to DAZ Studio. It is an image that can be used for providing a light source for rendering. You could Google it to find out lots more. The recent Iray render engine can use HDRI images to light scenes, and there is one that comes with Iray, and it loads by default.
It really is a wide ranging subject, HDRI can be used by the 3Delight render engine as well, and in many other software programs.
Do you have any specific questions about it?
So, it sounds like the idea is you just load this instead of creating specific lights sources and backgrounds. I got the yosemite HDRI in the bundle over the weekend, and eventually found it in the content library and brought it in. It seems to work fine in 3delight, but just shows blackness in Iray.
In Iray you apply the HDRI in the Environment group - click on Environment map and select it there. Play with the first two options for modes. Pick Finite Sphere, and rotate the image to cast the light the way you want it, rather than moving objects and camera.
While HDRs can provide light sources, it is not uncommon to also add scene lights as needed. These augment the environment light, providing things like fill, eye ligrts, back lights, rim light, and so on.
When picking HDR scenes, try to find those with good contrast, and if you want shadows, with a strong single point light source. Many of the free (and several paid) HDR's give a muted lighting because they don't contain much variance. Your results may be disappointing with these.
Many people use this one for learning (it's for non-commercial use only):
https://community.renderman.pixar.com/article/107/luxor-jr-panorama.html
it has a single very bright light source, so it gives distrinct blue sky daylight shadows. If the shadows are too harsh, add other scene lights for fill -- the same as if the scene were in real life.
When you stand outdoor there is actually light hitting you from all directions. The sky is scattering light, clouds reflect and scatter light, the ground and other objects around you are reflecting light at you. An unbiased render engine can raytrace all the relection off objects in the scene, but it would be extremely expensive to try to model the interaction of sunlight with the atmosphere and clouds. One solution used in 3D rendering is to use a picture of sky and surronding enviroment to specify the intensity of light coming from all directions. If you use just a regular JPEG image for this, you will not get a very good result. JPEG images cannot represent the dynamic range of a real sky with the sun. For this reason people use a High Dynamic Range Images (HDRI).
Now many HDRIs were not made with enough dynamic range to really represent the brightness of the sun. Many of the free HDRIs you can find are intended to be use with a distant light to represent the sun and aligned with the HDRI. In this case the HDRI is modeling the ambient light. Some render engines may have support for this HDRI+distant light kind of lighting, but Iray does not. This, of course, does not stop you from using those HDRIs with Iray and adding the distant light yourself. I know some of the sunny day outdoor HDRIs sold here in the DAZ store for Iray are bright enough to cast shadows without any additional scene lighting.
HDRIs for 3Delight usually use UberEnviroment 2 (UE2), and most I've seen also use a distant light for the sun but I'm not sure about the yosemite HDRIs.
It is fairly common for the HDRIs to be low resolution images. By default both Iray and UE2 do not show the HDRI picture in a render. They only use it for lighting the scene. They both have options to draw the HDRI in the render too, but many HDRI images are too low resolution for good renders. Many HDRI sets come with a low resolution HDRI to model the lighting and a high resolution JPEG image to use on a sky dome. This can be made to work well with UE2 in 3Delight, but it does not work in Iray. If you add a skydome in Iray, it will block the light from the HDRI.
There is a great list of free HDRI sources over in the freebies section:
http://www.daz3d.com/forums/discussion/57531/list-of-sites-with-free-hdri#latest
The quality and dynamic range varies widely, so just know that not all of these will give optimal results. Be sure to check the usage rights as well if you intend to sell anything rendered using the free resources.
Also, when using different HDRIs, be mindful of your tone mapping settings in the render settings. If your render is coming out darker (but not all black) than you want, try lowering the number in shutter speed or f-stop, or raising the ISO value. Or a combination of those. Do the opposite if the scene is coming out too bright or too many details are washed out.
Edit to add:
If you have access to Photoshop, you can selectively increase the exposure level of the sun in HDRIs that don't have good dynamic range. It is best to do this with HDRIs that aren't going to be visible in your render (i.e. "render dome" is turned off) since it the brightness of the objects in your scene will not match well with the background. You also don't want to increase it way too much as that ends up throwing the natural light balance from the HRDI way out of whack.
Alternately, you can lower the exposure level of light sources as well. I have done this with some indoor HDRIs where a stray light source was casting odd shadows on figures in the scene.
Just got a few from the Digidotz site which can be used in DS, Bryce, Poser, Blender, etc. What I would like to know is how to bring them into DAZ Studio and Bryce for use in those two programs. In DAZ Studio I use the 3Delight render engine, as my computers are not powerful enough for the other render engines available for DAZ Studio.
Basically I just want to know how to map an HDRI onto the environment sphere, or whatever is used for this purpose. Then I want to know how to tweak the light to make it brighter or dimmer.
Seems as though no one is able to answer my request. I shall look elsewhere, but will continue to revisit this thread to see if there are any new comments.
Check this out! There's a new product for both render engines in DS by Parris, the IBL Master. Here's the commercial thread with a lot of info on how to use it and other tips: https://www.daz3d.com/forums/discussion/215066/ibl-master-image-based-lighting-control-for-both-renderers-a-new-ibl-for-3delight-commercial/p1
Here.s the product site: https://www.daz3d.com/ibl-master-for-daz-studio
The big thing about this is that it is a light shader that solves the problem with global illumination and transmapped hair and vegetation so rendertimes are very fast compared to UE2.
In hdri lighting, if just using the light from the hdri, how does one remedy the "pasted on" appearance of a character that's in the scene, but looks as though he/she is "glued on" to a backgrouund image. I'm trying to achieve the sort of subtle ambient shadows that the character woud cast upon itself and the area or things around it.