Why is this Rendering sooooo dark???

[Zom-B]

I did a Scene for testing Light, a lamp on the ceiling that got 8 light Spheres...

The strange think about this, is that I simply can't light up the Room in this scene,
no matter how I try to tweak the Light settings! Also testing with biger scaling in Rainhard or
linear tonemapping don't satified me, the light just seems to Stop after some meters
The Walls are totally white (with some bump) but just don't reflect any light?!?

I Know I could light the room up, by using some biger Lights behind the camera,
but it should be possible this way too, and I wana know what I'm doing wrong!

Also strange is, that the untonemapped.exr is totally black! I used the Reinhard at 1 1...

Here is the Render:


Here the C4D view:


And >>HERE<< the Scene Files + C4D Source.

[Kosmokrator]

your wall material is difuse or plastic?if is difuse try a litle glossy plastic like mat and see......

[psor]

Heya Zom-B,

I will take a guess. I'm not sure if you have the option to use
f-stop and shutterspeed in the cinema plugin. U3dreal has put
a lot of effort into the max plugin to offer such an option. He
is using the linear tonemapping for this. So I did a quick test
on your scene and changed the tonemapping to linear with an
value of 35000 and the room gets much brighter.

So I think it is like a real camera, you have to lower the
shutterspeed to get more light into the lens and this way get
a brighter image. Well ... since Indigo does not have native
support for shutterspeed and f-stop we have to use this
workaround. I could be a bit wrong here ... 'cause I'm already
tired ... hehe. ;o)

Hope this'll get you somewhere.


take care
psor

[Zom-B]

Yeah, Linear Tonemapping helps here "somehow", but the Image get totally "over bright"...

At the moment the C4D Exporter is very basic, just beeing able to use all Indigo functions, what is good enoug atm !

Here a Example with Linear TM at "just" 25000:


I checked the unmapped.exr again, and found out, that they are not totally black, but very very very very dark!
while coverting this 32bit to 8bit in PS you got to put "lighten" to +10 (!!!)
to get a result, same as my rendering at first posting...

As far as I could say, the problem is in the Light Sources!!!1!

There is no light information for the Light Speheres beyond the 8bit (or 16bit) colordepth!!!
So there is no light brigh enough to kill the "32bit darkness"!?

I may be totally wrong!!!!

could be a bit wrong here ... 'cause I'm already
tired ... hehe. ;o)

He he... yeah at 4 clock in the morning you are allowed to be tired

[psor]

Yeah, Linear Tonemapping helps here "somehow", but the Image get totally "over bright"...

At the moment the C4D Exporter is very basic, just beeing able to use all Indigo functions, what is good enoug atm !

Here a Example with Linear TM at "just" 25000:


I checked the unmapped.exr again, and found out, that they are not totally black, but very very very very dark!
while coverting this 32bit to 8bit in PS you got to put "lighten" to +10 (!!!)
to get a result, same as my rendering at first posting...

As far as I could say, the problem is in the Light Sources!!!1!

There is no light information for the Light Speheres beyond the 8bit colordepth!!!
So there is no light brigh enough to.... ähm... be bright!

Tell me if I'm wrong!

could be a bit wrong here ... 'cause I'm already
tired ... hehe. ;o)

He he... yeah at 4 clock in the morning you are allowed to be tired

Danke Anke!

Erm, ... first I thought darn why is your new image that overbright,
mine was looking like this with linearTM@35000:


... well I changed the meshlight to peak first ... *LOL*

Code: Select all

    <meshlight>
        <pos>0 0 0</pos>
        <scale>0.010000</scale>
        <mesh_name>light0</mesh_name>
        <spectrum>
            <!--blackbody>
                <temperature>6500.000000</temperature>
                <gain>0.00001</gain>
            </blackbody-->
            <peak>
                <peak_min>300.000000</peak_min>
                <peak_width>550.000000</peak_width>
                <base_value>0.000000</base_value>
                <peak_value>200.000000</peak_value>
            </peak>
        </spectrum>
    </meshlight>

I guess we need some insight of Nick ...



take care
psor

[Zom-B]

Oh yes... peak isn't this bright as BlackBody is >>looky looky<<.
I shoud try with RGB light and Linear TM!

Somehow I miss a upscalable Lightsource to 32bit total white, this would be perhapes usefull...

Would be nice if Nic could drop some words in here, tested settings etc. for 5h today

[psor]

Looky, looky ... spooky, spooky ...

It looks like the "balance" is way off and that the reinhard Tonemapping
will scale it almost to zero ... erm, ... I feel like I should hit the sack right
now .... *LOOOL* Well ... seriously, I have to read a bit about the TM
stuff ... at this point I feel a bit overloaded.


take care
psor

[Zom-B]

OK I tried a last one using RGB lights and Linear TM...
I needed a scale of 10'000'000 ( ) to get a result somehow usable:




The unmapped.exr is so messed up, its only 100 KB small and contains,
just very very low level color Information, check it out >>HERE<<

Now I understood why TM kills RGB lights if you use other Lightsorces like BlackBody or Peak...
BlackBody its about 400 times brighter tahn RGB Light, and Peak is 285 Times Brighter!
(Values are very imprecise calculated by the different scale of Linear TM for the 3 Types of Ligt to get a nearly same result)

[OnoSendai]

Hmm... not sure what to say here.
The blackbody spectrum type can produce very different intensities from the other types, depending on the temperature.
Also with Reinhard tone mapping, there is an automatic scaling so that the lightest pixel gets mapped to (1,1,1) (more or less).
So you have to mess round with the gain parameter of the blackbody type to get it right. The totally black exr thing *is* a problem tho, perhaps it's due as Zom-B says to the pixel values getting rounded/clipped to zero.
I'll fix it soon

[Zom-B]

Hey Nic, thanks for reply...

I just Played around with the gain value of Black Body!
It seems my conclusion with not 32bit scalable Light Sources isn't right!!!!!1!

At a Gain of 1 BlackBody do nice (nearly) pure white Light Spheres (at 6500 & D65) in the untonemapped.exr!
Scaling it to 100 its totaly overbrighten, scaling it to 0.001 its so black as in the first Post tests!
It it possibly intersting to think about some new default values for Exporter Coders for Lights (BlackBody gain at 1)...

But now back to the main Problem... why does this Lamps couldn't bright up the room!

I did some new tests, and also get a very interesting answer for this!
Her a UNTONEMAPPED Picture (1885 mutations per pixel) :

Same Picture after Rainhard:


Now I moved the Camera down, so the Light spheres are out of the Scene:
Her a UNTONEMAPPED Picture (3300 mutations per pixel) :

Same Picture after Rainhard:


So Reinhard behave like your Eyes do, to complicated to explain in english for me,
but >>Here<< a quick link to a example how HDR is used in "HL2: Lost Coast" it simulates the Human Eye reaction to bright light.

Back to to main question:
Why does the totally 1,1,1 white walls don't reflect the Light of the Spheres in the untonemapped picture?
Why is Tonemapping needed to raise the brightness of the walls?
This Black Body lights are done with a gain of 1.

BTW:
How acurated does Indigo Renders before calculating down to 32bit???
I know C4D renders in 96Bit Collor before down calculation...

[OnoSendai]

If the walls are highly reflective (e.g. RGB colour is high), then the light will bounce around a lot, leading to quite uniform lighting. Try setting the rgb colour to like (0.6, 0.6, 0.6)

[Zom-B]

Phuuuu.... I get more confused after each posting here!

Here a Test with the 0.6, 0.6, 0.6 Settings for the wall!
Again Reinhard 1, 1.

Indigo PNG Output (1186 mutations per pixel) : :


Indigo untonemapped EXR File:


This Time I also saved the Tonemapped EXR File, and look at this:


It seems the tonemapped EXR ist the File I allways aimed for!!!
So the question now is... what is the PNG file Indigo saves by default???
I allways thought its the tonemapped image at 8bit?!?

[Zom-B]

I rendered the first post scene again in v0.62, to see if something changed...
I used the exactly same settings (only BiDir is enabled now!) to get a better comparison!

Here a render after 2h 975 mutations per Pixel rendered on 2 PCs (I'll update later ):


Still a lot of this fireflyes remaining, but I got enough time

**EDIT**
Totaly forgot the Render , so her a rendering after 22h 7827 mutations per Pixel:



The Fireflys needed long time to leave, I think its because of the BumbMap on the walls...

The picture now gets much brighter than before... very nice!
I'll keep testing... I'm interested about the best "default" values for light
so in untonemapped.exr the color ist 255,255,255 (for black body its somewhere less than gain 1).
This default values are perhapes interesting for understanding the light parameters in indigo better,
and also for dafault settings for Exporters.