View Full Version : Hot spots / White spots in render

02-12-2014, 05:54 AM
After feeling happy that I got Fiberfx refracting with the 'volume only' option. I now have a scattering of hot/white pixels that go over 1000% rgb values when sampling them in the image viewer.


I wonder if anyone else have come across this kind of thing? No GI, Ray Recursion Limit: 20. I'm thinking it must come from refracting the fur?

Thanks for any feedback :)

02-12-2014, 06:11 AM
Maybe try render and export different buffers and corect this in Photoshop.

02-12-2014, 07:42 AM
Thanks Marcus, want to ultimately animate them so I'm gunna keep looking for a fix in LW. Definitely something not playing nice with FiberFX and transparency.


02-12-2014, 08:37 AM
If you're using Global Illumination, sometimes those hotspots can show up unless you have "Limit Dynamic Range" ticked.

02-12-2014, 08:48 AM
That would be my guess too. Take care about very high values in HDR environments.

02-12-2014, 08:49 AM
No GI in the scene, 2x area lights. I've also tried the Limited Dynamic Range but have the same results :S Thanks for the help

02-12-2014, 08:57 AM
If there's no GI it could be the light and or the shading samples being to low.

02-12-2014, 09:17 AM
Thanks for the help, just tried 4 and them 12 for light and shading sample and it still has the hot spots. However they do seem to move around with the different sample numbers :S


02-12-2014, 09:20 AM
Do you have very luminous polygons in your scene? Or a very tiny bump scale?

02-12-2014, 09:37 AM
What type of transparency shader have you got there? I remember one coming up with high results (may have been a bug now fixed..), clamping it nodally worked back then but it is a while back. Is it the Fresnel like one? Clamp it to 0 and 1 and see what it does. I know it is playing nice with the backdrop, but it is worth a shot.

Also, regardless of the transparency issue, you seem to have some full white pixels near the top of your furry character.

My bet is that both are some FFX bug.. Safe bet :)

ps: Nice work! But do you need a recursion of 20?

02-12-2014, 10:49 AM
Thanks guys!

I do have luminous polys to look like soft boxes and get caught in reflections and 120% Luminousity, no real tiny bump scale's. Transparency is make with gradient on incidence angle 0-100%. I was trying recursion cranked up to see if that help (which it didn't).

Did a render with FFX off and it's annoyingly fine :) might have more of a play with the FFX settings.


02-12-2014, 12:04 PM
Try Dielectric node for the glass?

Side note: They are all very cute!! it's a shame the face of the furry guy is being overwhelmed by the hair.

02-12-2014, 12:42 PM
When sum of diffuse+specularity+reflection (and maybe +refraction) is exceeding 100%, after reflection bounces they will add up together..

If you have diffuse 100% white color, and specular 100% white color and 100% white light color, then obviously in some pixels will have 200%,200%,200% rgb values..
Then imagine what happens if other reflective surface will find it during ray-tracing and add to it's own color.

02-12-2014, 03:00 PM
yes yes, but he knows all that.

Reproduced your bug 2create, wasn't too hard. If a thread shows "FFX" and *insert random issue* it is usually a safe bet to go directly for bughunting imho. If you delete the inner poly's on that glass surface I bet it renders fine. Damn weird bug too, it lights up the entire edge of my fur object. The same thing is showing for you, but only on specific places. Perhaps you use different sampling, AS or whatever.
Will post my simple scene so you can bug report if it indeed is the same bug (you never know with FFX!)

reproduced bug:

Hot pixels showing in reflection (and changing on the fur, something is going wrong in the FFX with the bounces):


delete the inner poly's of the glass and all is well again. Clearly a FFX bug.
I wish you good luck and hope it will be the last one you'll encounter.

ps: setting the recursion limit to 4 (just enough to pass through the glass) it is gone here too. set it to 5 and it is there.

02-13-2014, 05:16 AM
Cool thanks for reproducing this Hieron, deleting the inner poly renders just fine with FFX behind :) I'll check out the scene and look to submit a bug. Thanks again!

02-13-2014, 07:07 AM
Cool thanks for reproducing this Hieron, deleting the inner poly renders just fine with FFX behind :) I'll check out the scene and look to submit a bug. Thanks again!

No problem!

Nice work that you guys are doing btw. Will look forward to your results with this scene, hope to see it one day.