View Full Version : How to control pronounced highlights

11-21-2014, 07:59 PM
Hi folks,

this is my first attempt of getting through the modeling and rendering process with LW ... so far everything went pretty nice. But now I am stuck with some pronounced highlights coming from the environment mapping. I am using a dome light with a 'Gray Sky & Cool Sun' environment map.

On the render there are coming up some tiny highlight spots over the model in places where I wouldn't expect them ... and they seem a bit too harsh o pronounced to me. To minimize 'em I tried several settings in the Render dialog, such as Reconstruction Filter and Soft Filter but all of them did affect the image quality by a way I was not after. For this renders, the shading and lighting samples are both at 8.

See images below.




11-22-2014, 06:13 AM
They are very noticeable on the second image. Not sure what you mean by the environment map is that an HDRI image? If so, then apply a full presicion blur filter on the hdri in the image editor. Other things to tweak are the specularity but that looks fine except on those hot spots. And lastly you can try to activate "limit dynamic range" in the render tab.

11-22-2014, 08:47 AM
Yes I'm using an HDRI image as 'Image World'. In the meanwhile I am doing some renders with another HDRI image to rule out it may something related to the image. With the other image, of course the reflections changed but the problem with the pronounced hightlights continues.

Lastely when trying the "limit dynamic range" as you suggested I could perceive a noticeable improvement. Still trying some other tweaks. Seems that I am on the right track now.

Thanks a lot.

11-22-2014, 09:49 AM
Yes it will turn out to be the sun in your HDRI. Very nice model and render otherwise.

11-22-2014, 10:29 AM
Hi I did some more renders on that subject. Basically the "Limit Dymanic Range" did the trick. Other settings are Shading Samples 1, Light Samples 8, with Adaptive Sampling 1/9 in Camera.

I added two additional renders where I used the freshly acquired light probes from illuminatedtools.com (http://illuminatedtools.com/) offered here in the forum section. I think the "Elevator" does a good job here.

Original Cool Sky Probe

Subway Interior (http://illuminatedtools.com/library/int/int_day_subwaytrain/)

Elevator Interior (http://illuminatedtools.com/library/int/int_elevator_metal/)


11-24-2014, 02:42 AM
Looking good, what Limit Dynamic Range does is basically cap the luminous areas of your render to 256 before antialiasing so it doesn't have to try to smooth an area with 1000 to an area with 10 luminosity (it will fail to antialias correctly). You do however lose the ability to export to a high-dynamic-range image.

11-24-2014, 01:29 PM
For preserving dynamic range with nice AA you might want to take a look at this thread (http://forums.newtek.com/showthread.php?144533-Aliasing-does-not-go-away-what-am-I-doing-wrong&p=1409694#post1409694) http://forums.newtek.com/images/icons/icon7.png


11-24-2014, 03:00 PM
Thanks for your valuable hints. The "preserving dynamic range" thread is quite advanced stuff ;-)

I never thought of that such things would be possible directly in LW.

For now I am going to model some more stuff to complete the scene and pretend to do some basic rigging too.

This will keep me busy for an hour or two ;-)


11-24-2014, 11:12 PM
As was mentioned, you could also try blurring the image. You could also try making a fairly low resolution version of the HDRI you're using. That would have the same effect as blurring the image and save memory.

Apparently, LW2015 has a solution, but we don't all have $495 in our pockets at the moment. :)

11-25-2014, 12:32 PM
Blurring the image does help for reflection highlights but we need to be carefull for not overdoing it and changing the overall contrast ratio too much on the diffuse shading, otherwise the lighting characterization will be lost. In such case, a low-res version helps in conjuction with the blurring trick in the sense that we need lesser kernel size for the convolution (besides the memory savings already mentioned). A low-res version alone may also help for getting rid of sharp reflection artifacts due to very bright details in the HDR map, however a low-res version alone will help very little for antialiasing the overall bright areas.



The 180 pixels version of the 6144 pixels HDRI doesn't make any difference in the aliased area of the alien's head.

In this case the proposed AA recovery trick is still able to help even:


The new importance sampling solution helps for avoiding sampling artifacts being that it will distribute more efficiently the fired rays (Multi-Importance Sampling will help even more for shading), but it won't help for the aliasing artifacts shown previously. Just in case, DP Dome Light (http://dpont.pagesperso-orange.fr/plugins/lights/Additional_Lights.html) has also an Importance Sampling solution which works in previous LW2015 versions too.


11-25-2014, 02:34 PM
The release of LW2015 is a bit of bad luck to me ... Since I bought 11.6.3 just a couple of days ago :-(

11-25-2014, 10:15 PM
Gerardo, thanks for the info with pictures. :)

Caustics, contact customer service and see if they'll upgrade you. I don't know if they will, but it doesn't hurt to ask. :)