TexSky VS HDRi comparison
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hello all,
who here uses HDRi maps in their Sketchup + VRay renderings?
i made a quick comparison between the HDRi lighting and VRay Sky lighting (with both of them using a HDRi texture in the BG slot in Environment tab), and the attached screenshots are what i came up with.
i am more and more persuaded that the combination of VRay Sky as the light source with an HDRi image as the background is the best option available, both in terms of workflow and speed - the HDRis' various resolutions require a lot of guessing of exposure and IM&LC settings, their final lighting quality is still questionable and they take more time to render at same settings.
however, it may be that i'm doing something wrong, so if anyone had any tips about HDRi workflow, my ears are open.
the screenshots:
[xxl-img:3kozemj7]http://i.imgur.com/icppd.png[/xxl-img:3kozemj7]
[xxl-img:3kozemj7]http://i.imgur.com/1szP8.png[/xxl-img:3kozemj7] -
I use a combo of VRay Sun along with a HDRI that has been blurred for GI. See this video tutorial http://www.youtube.com/watch?v=D3-TxEzW4sQ. You cannot use an out-of-the-box HDRI because this version of the plugin does not support dome lighting and you get splotches. If you open the HDRI in Photoshop and Gaussian blur it then save out a separate file and use this as your GI and use the original as your background, you will get great results. In order to bring in casted shadows you have to bring the sky back in using a tricky workaround.
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thanks valerostudio, that's exactly the tutorial i followed and the settings are the same
the only diference was that i actually did use out-of-the-box hdri image, but had to increase HSph to 100 and Samples to 55 to get rid of the splotches (these numbers are the same in both scenes, but with Sky lighting only i can reduce the numbers to 50/25).
the advantage is that i can retain using the camera's exposure controls.
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I use HDRI's from time to time - if I have many views in different directions. If it's one or two directions I often just Photoshop. But lately I've been having some nice results from combining Sky and HDRI for GI source - allowing me to get much softer shadows with the nice colours HDRI gives.
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thomthom, do you have any examples available?
when you mention the soft shadows - i actually forgot that my comparison is viable only in the 'sunny day' situations. if the sky was overcast, soft shadows might actually come in handy... hmm. more testing involving real-life photography needed.
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@eidam655 said:
thomthom, do you have any examples available?
Trying to remember what projects I used the technique with....
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I hope that Dome Light is in the works for the next release. If you have ever used this feature in Max along with a nice HDRI, like Peter Gunthrie's, the results are fantastic! Well worth the minimal cost. http://3docean.net/user/paguthrie/portfolio
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I did try out using higher IR subdiv values with an unblurred HDRI and it does seem to work well. I did test it with a Peter Gunthrie file and it looks really nice. I guess I always was under the impression that you could not do this without getting splotches. It may also depend on the resolution of the HDRI as well.
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valerostudio, that's exactly what i found out.
at first i had a scene set up with vray sky only and then decided to put the hdri into the same scene following familiar Fernando's settings. it turned out to be way too bright, so i had to began messing around with the settings.
so first thing i tried was just to create a blurred version - to my surprise, it didn't erase the splotches.
then i tried to scale it down - splotches gone, severely underexposed (and i believe this is the reason Fernando suggests to give up vray's physical camera exposure controls, the iso/shutter/f-stop values would not make sense if they had to be set to extremes).
while the test images were rendering i was reading the vray documentation and realized how HSph value actually works (determines the lighting half-sphere subdivisions) - so to retain exposure controls (to be able to use the hi-res hdri) and to get rid of splotches (as blurring the image didn't work) i increased those HSph and Samples values.the physics worked. although the rendering time got quite severely prolonged.
i'll try 3DSMax's Dome Light, when i'll have time again. sounds like a simplification of matters.
PS: i tested it with PGuthrie's "1325" HDRi map, which comes at ~7k px width i think.
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I think the reasoning behind the workaround with blurring the HDRI and using it along with VRSky is to save on render times. Increasing those IR map subdiv increase times dramatically. You need to be around 100 in order for the splotches to clean up. If you use a blurred HDRI, you can use lower values like 35 and still get good lighting results. Dome light solves this because the HDRI is mapped to a dome close to your model, when you an HDRI as an environment, its mapped to a giant dome that lives around SU space, and this is why you end up with splotches.
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I have a problem which is close to this topic. My background is too close to the object. How can I minimize or zoom it out?
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mmm.. maybe you can try to resize the model.. not sure..
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