View Full Version : HDRI very noisy render

01-14-2004, 09:14 AM
Hi :)

it's been a long time i didn't do some high quality rendering expecially with HDRI (i'm quite using more lightwave for low poly modelling and very simple rendering)

anyway i got this results :(

first the reference pic with no HDRI
just simple reflection and fast fresnel

now i added an HDRI pic from debevec (the forest).
the plug "Image World" in add environement in the backdrop menu

its 4x12 backdrop radiosity with no AA
but it's really noisy isn't it :(

i tried to reduce with 10x30 radio and noise reduction shader + lowAA

better! but i think it will be too long for a more complex scene.

where did i do something wrong :confused:
anyone can help me please :)

01-14-2004, 09:34 AM
Try blurring the HDR in the image editor (using the FBlur image filter).
If you still want sharp reflections, create a clone of the image, blur the clone and use it for lighting, use the original for reflections.

01-14-2004, 09:37 AM
oh ok :) i was afraid i made some mistake somewhere!

so it's coming form the hdr map!
ok thanks! :D

01-15-2004, 04:37 PM
renders are unusable if you use a 96 bit image as your global ilumination lightsource, even with shading noise reduction and very high levels of AA. The only way I can get a usable image rendered is to first convert the 96 bit image to a 24 bit image. The trouble with HDRI renders comes from 96 bit images on all 3 systems I use--a G4, an iBook and a dual Pentium PC--happens with ever render. The only solution I have found is to convert to 24 bit. I know that seems to defeat the purpose of using a 96 bit image in the first place.

I've tried using 96 bit images as both Image World for light probes and I've also tried 96 bit panoramic images as spherical maps(in the color portion of the surface editor with luminace at 100% and no ambient or lights)
Both of these methods fail to produce usable results; the images are grainy and have yellow specks everywhere.

If anyone has a suggestions on how to use a 96 bit image as a source of global illumination(that yields *useable* results) I'm eager to hear them.

01-15-2004, 06:01 PM
well with 24bits you lost all the goal to use hdri :(
i will look for other hdri maps. even maybe do my own.

right now i'm not working on it. i will see this later...

01-15-2004, 07:39 PM
try that,
open image editor, select image, and in image filter tab apply Hdr exposure, and play with it.

this filter work like a stabilizer, which limit some part of HDR info, and give you a more clean and fast lighting.

HDR blurring is an old suggest of Devebec to avoid noising and flashing during animation. If you add a slight blur to image used to lighting, you avoid to find a single pixel fire a light ray sometimes during animation.

i tell sometimes be cause due the randow nature of radiosity implementation of lw, not all pixel are used in every pass.

to have a good radiosity with HDR, enable motion blur, which cause a best and fine light sampling during every pass of antialias, if is not enable, lw do a single sample, than do antialias, if is enable lw do many sample, one for every antialias pass.

good work

01-15-2004, 07:54 PM
I tried that. The motion blur and blurring the image itself are useless. Like I posted before, the problem seems to come from it being a 96 bit image. I'll have to post some examples that help clarify it. Besides that you shouldn't have to blue the image to get good results.

One other detail I forgot to mention: if I radiosity render a scene containing objects that have surfaces that are bright light sources--for instance a model of a laptop with a polygon in the screen whose surface has a luminosity of 100% or above, it will render perfectly. Place a 24 bit screen shot in the color portion of its surface, it will still render fine. Replace that image with a 96 bit image--*any* 96 bit image--and you have a grainy, speckled unusable mess of a render.

This happens on my iBook with version 7.5a, on my G4 with 7.5b and on the PC with 7.5c.

I hope NewTek fixes this in 8.0 or at least provides a concise explanation of how to correctly use a 96 bit image as a source of global illumination in the new manuals.:confused:

01-15-2004, 08:41 PM
hi, moggbomber
here you can see a render like your,

with montecarlo 4 x12, no aa, no noise reduction, nude and crude render.


like you can see, no grain (a bit of griny is jpeg compression).
i attach scene to check (without hdr which is too big)

i add like i tell you a filter hdr exposure to normalize the light of hdr.
good luck.

the fact is that, like usual Newtek give us a powerful tool like HDR, but not explain how to use it correctly. i see similar situation for other software, but many tutorial born fast with lw user experience...

p.s. a big tips when you have a too bright surface is to reduce a lot the diffuse parameter.

03-31-2004, 04:43 AM
Ive found that all the "seigo" HDR image probes are very good images and dont give u that speckling. from what ive found, even in Fprime with monte carlo rendering, if the hdr isnt good it will give u that speckling. so i dont think its ever really the RAD- mode, or setting, its seems the hdr is usually the culprit. Granted, if your doing an animation then u need to be wary of light flickering with using radiosity. Ive been quite happy with Fprime, cuz using say monte carlo, or ever backdrop i think will give u flicker free animation