Your advice in using hdri ?

one of my bad habits is using hdri background whenever I can and ignorantly hope that can beautify my render (they created an environment for reflection and also help lighting, is that good ?). In fact, some hdr give really ugly result, I attached here some renders made with different hdr lightings, as you can see, some of them are good, some are unacceptable (the noisy one). At last, some questions’ popped out from my head, how do you define a good hdr image for a specific scene ? When is using normal lamp rig better than hdr lighting ? Is hdr background the only way for reflection ?

All were rendered in yafaray with the same settings.
http://img27.imageshack.us/img27/5281/hdrcmp.jpg
By hecklervn at 2011-06-18

The trick to good HDRI is to use different resolution images for different passes. The lighting should ideally be done by a blurry, low res HDRI image to reduce the noise. You don’t need detail for the light colors. The reflection should be a simple large JPEG of the scene. You want this to be high res. And the environment should be a high res HDRI image. There are tools that will take a high-res HDR image and create the rest for you, a good one was on Blender Nation maybe a little more than a month ago I think. In any case, I haven’t found a way to do this correctly the way I’ve described without compositing in Blender, but when you get it working it makes for a scene with very natural lighting that also renders very quickly.

There’s a couple of good links to hdri sets available in the following post:
http://forums.luxology.com/discussion/topic.aspx?id=57221

As per m9105826’s explanation, you will find multiple images per set,
respectively some of them higher some of them lower resolution.

I suggest checking out Bob Groothuis website for some high quality & value IBL sets.

Thank you, as you said “low res HDRI image reduce the noise” why some hdr always give noisy result even after I reduced their resolution (I have tried with the 3th one in my attached) ?
Another thing, can anyone load successfully extremely high res hdr (~100Mb) in Blender ?

Try using a gaussian blur on the image you’re using as well. It will help remove a lot of noise. If you’re still getting too much noise, increase the samples by 2 and repeat until it’s gone. If you’re above 10-12 samples and theres still noise, however, post the scene here and I’ll try to see what the problem is.

As far as large images in Blender, I know some people in the past have had problems with them, but I’ve always been able to open them. It may be a RAM issue; I have 16GB of RAM so I wouldn’t expect it to be a problem, but if someone had like 2GB total and other programs open it would definitely cause a problem.

Start collecting them and making your own, I have a favourite one I use for everything, but all my images are starting to look similar…

also, separating the enviroment pass can make it easier to remove noise and correct any nasty colours with the compositor.

I know this is an odd place to ask this question, but it sounds like you might have the answer. If I’m separating things into layers, what do I need to enable/disable to have a render layer in the compositor that is just the sky or just the background with stars? Whenever I try what I think would be the common sense way to do it, I only get a black/blank render layer.

sorry, forgot to check this thread… :stuck_out_tongue:
For your lighting, you’ll want to separate the Environment pass for the compositor:
http://www.pasteall.org/pic/show.php?id=13997
and use reflection mapping for shiny objects.
http://www.pasteall.org/pic/show.php?id=13998

Great! I’ll give it a try. I kept thinking checking the ‘sky’ box was what I needed to get the proper pass for my background layer. Thanks!

If I remember rightly, Yafaray blurs hdr images internally for lighting, and uses the sharp version for reflections, so pre-blurring probably won’t help much.

Noise in hdr lit renders is usually caused by small, bright light sources in the image.

You could try increasing samples for the lighting, and any residual noise can be cleared by increasing Samples and AA Samples. For these kinds of hdri you just have to accept it will take longer to obtain a clean render.

Anyone can load hi-res hdr images if they have enough RAM.

Thank you, but in fact I can load that huge hdri in Maya or Cinema4D, only Blender gives the error “cannot get an image
My system has 2gb of ram

Did you try another build? I haven’t got any problem to load big HDR maps…

I just tried loading a 142mb hdri. It uses 1.5 GB RAM to load it and rendering the default cube uses nearly 3 GB. (I have some other applications open at the same time)

Do you use 32 bit Windows? I remember reading some versions of Windows will not allow an application to use more than 1.5 GB RAM. I don’t know whether that error indicates a lack of RAM, but it is possible the operating system is preventing Blender accessing enough RAM to load the image.

Maybe my system is the cause of that error, I couldn’t load the large hdr in both XP and Seven :frowning: I must say I hate my machine :frowning: