Anybody have a problem like this? I just used a sample of the HDRI file from Paul Debevec's site (st_peters_probe.hdr) and translated it via HDRShop to a longitude/Latitude map. The problem is that I get this artifacting (circled) when I render. This may be caused by my settings not being precise enough, but I thought I'd sound off anyway. Suggestions? The image shows my current render settings as well Ken 

I don't know the fix, but you have ray-tracing turned off, and it reminds me of what we used to get in C 1.1 with terrains that were rendered in the hybrid ray-tracer.

Ken, You might want to crank up the interpolation precision a bit. I've not had problems quite this bad but similiar. I have found that the filter sharpness and interpolation precision can have a big impact. You might want to also up you photon count a bit. As for the previous post, I have found that full raytracing is in fact NOT required if you're doing HDRI only and there are no lights! I'm finding myself becoming very lazy in my lighting because HDRI can produce some very nice reflection and lighting effects. As most of my images have been boring green product shots I do a quick low res render to check the ligting intensity and then leaving it rendering over night with all the settings high. There are some nice HDRIs on the C3 disk 2 that work well. I'm hoping to have time over Xmas to learn how to create my own HDRIs which at this time of year in Calgary will have a lot of snow in them. Andrew *<:=

Ive had problems like that before as well, fire up Full Raytracing and that should take care of your problem. E

I decided in the past that interpolation was the big evil-doer. Turn it up high or turn it off (and get some sleep for free, because it takes a lot longer to render). And planes and infinite planes are the first to show this kind of artefacts. I suppose the interpolation works the same as, for instance, the jpg compression method, where calculations are made for a larger part of the surface. The lower the interpolation number, the larger the chunks that are treated as one 'lighted area'.

OK, here's the sitch... I tried different renders using all of the mentioned solutions... Final Verdict: Full raytracing: This has absolutley no effect on the artifacting in the render. What this does do is sharpen the reflection on the sphere/cone structure. Good thing, but not a viable workaround. Adds to render time only slightly. Interpolation: This did not visibly affect the image, except to add to render time. No go... Photon Counts: This changed the size of the artifacting and made it smaller, but did not remove the problem. Also added to the render times.... All settings to best/lowest value: This solved the problem, but it went from a 2 minute render to a 40 minute render... gotta be a better way. Final conclusion to render artifacts (after much testing): Change the lighting quality out of fast mode to best mode. This allowed the lighting to fully reflect off the white base object and be accurately portrayed. Artifacting was removed and the final render time was only 5 minutes more (at 7 minutes total) than the original. Thanks for the excellent advice, guys, as it gave me a starting point for figuring this out. I'm going to keep working on HDRI as a means for natural lighting. Just FYI, setting a spherical camera in a scene that is 2:1 ratio will yield a HDRI lat/long map. Use GI and you can just translate the image using HDRshop to an HDR image that carrara can use! Ken 

Here's a test using a "home-grown" HDRI map built in C3! Same basic object as above, but using my map (inset) instead of the one produced by Paul Debevec. Ken 

Is your HDRI image produsing any light? All your surfaces are reflective. How about dropping in a non-reflective object?

tkane, there are no lights in this image at all, just the HDR image driving all lighting. The only non-reflecting object is the plane which they are sitting on. Three objects total: The plane, the sphere, and the cone. Ken

I understand your setup. The reflective objects will reflect the background whether it's an background image or HDRI image. I was asking because the plane (which is not very reflective) is very dark as though it was not receiving light. I have tried to create an HDRI image and it looked great with reflective objects. But once I added non-reflective objects, it showed me that my HDRI was not generating any light. That's why I was asking you to put in non-reflective objects to see how much light you are really getting from the HDRI image.

OK, here'a a test render. There is obviously light coming from the HDRI as I've jacked up the skylight intensity in the render settings. The attached image has a number of objects, some reflective, some not. The numbers show the skylight intensity settings in the render panel. As you can see, there is a marked difference. The HDR image just doesn't have the range of the other captured HDR image I used, but it does light the scene. I intentionally used a low light setting as this is a darkened room with a "pseudo" studio light prop. Pseudo meaning it has a few objects that glow in an approximation of a lighting rig in a studio. I think it is working, but I will have to test to be sure. Ken 

I have only a rudimentary understanding of HDRI lighting so maybe this question will sound off base but... If you just convert a spherical camera rendering to *.hdr file don't you end up with a "LDRI"? Low dynamic range image? Wouldn't this only approximate true HDRI lighting when used in C3? Would it be possible to "expand the range" of the C3 "LDRI" with different "exposures" in C3.? I think I've seen this talked about somewhere. Sorry for all the quotes! Ed

Ed, very perceptive and very true. I'm not at all sure how I would go about simulating exposure settings in C3, but I'm sure it can be done. Right now I only use one image to set up the shot, so I guess, yes, it would be LDR. For what it's worth, though, it seems to work just fine for what I am looking for. But for specifics, I am VERY sure that by using GI images to create the HDR file (whether HDRI or LDRI) it is a better approximation of natural lighting than just adding in a straight ray trace without GI. Maybe I'm rambling.... ?? Ken

Ken, Thanks for the reply. I think you should also be thanked for such a good post of the results of your experimentation. Really helps all of us.

If you are making your own HDRI images from digital photos, either from a probe, or just a straight picture, one exposure will work, but will be a LDI(low dynamic image). It will light the scene but only in a very general way, but will provide good reflections. Try bracketing the main exposure with shots 1 or 2 stops up and down, or as many stops as you like. Then combine them in HDRIshop. The lighting will become more scene specific, shadows will harden where they should, espcialy if there is a sun in the shot! Don't forget to use a tripod, as the frame must register.

So maybe we could try different renders with different light intesities? Or maybe we just get into a chicken and egg situation! Almost Always Confused Ed