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Where is the HIGH Dynamic Range ? lost I fear...
Posted: Sat Jul 02, 2005 9:19 am
by Hervé
Hello ,these two renders where made with professional HDRI from Dosch Design.
Well, first I think the Dynamic range is somehow lost during the transfer into MXI, in the 2 examples , I have oriented the camera facing north and south (also the decor , as I first thought even if I move or oriented the sphere dome, nothing changed)
well look at the first... the sun is facing the camera (almost contre-jour), so the wall facing the camera should be much darker. Now look at the second render, this yime , the sun is behind, so the wall should receive much more light, also as you can see spherical mapping in LW looks like open GL exactly (maybe an info for you NL Team) off course, rendering with the same HDRI gives much better results in LW..
Don t take me wrong, when checking, it looks like the place in this hdri where the sun appears is about one million times brighter than the sky, well it does not look like in Maxwell...
BTW, Tom said the same, that is : no difference between LDR and HDR images

Posted: Sat Jul 02, 2005 9:24 am
by tom
Hehe....
Nooo... I didn't say HDR is the same with LDR in Maxwell.

I said that it's practically hard to differ HDR/LDR illumination for most scenes.
Posted: Sat Jul 02, 2005 9:30 am
by Hervé
tom wrote:Hehe....
Nooo... I didn't say HDR is the same with LDR in Maxwell.

I said that it's practically hard to differ HDR/LDR illumination for most scenes.
Tom, for once, let's not play with words... I'd say maybe 10% better... but too bad... is there a fix in the air... like Love is in the air, everywhere I look around... love boat.... ta da da da da da...

Posted: Sat Jul 02, 2005 9:34 am
by tom
So, do you really think there's something wrong with HDR to MXI conversion?
Posted: Sat Jul 02, 2005 9:55 am
by Hervé
I am just a stupido artist, not a coder... but if someone at NL could test it.... dunno..., I am rendering now a 360° pano with F_prime, and the result is 2 moons of difference... I'll post result later...
too bad there are no ways of opening an MXI converted, and see where are hot spots... like in LW viewer... I point the mouse, and it says how much light tere is at that spot....

Posted: Sat Jul 02, 2005 10:17 am
by Micha
Herve,
is the second image the M~R? My experience is, that you must change the gamma to a lower value for better light contrast. Maybe, here is the difference between your images.
If you try to test the lighting of a HDRI, I recommend to use a grey objects at a grey ground. So, you can better see shadows and lighting.
Posted: Sat Jul 02, 2005 10:28 am
by Maximus3D
I ran into a odd problem last night when doing a HDRI test with Maxwell, i got no shadows at all, nothing, it was just nice clean reflections from the HDRI map and that's it. And i tried, i used the Kitchen map from the web, i tried the Cathedral and several others. All showed the same result, no shadows. Anyone else got the same or is it just me ?
/ Max
Posted: Sat Jul 02, 2005 10:37 am
by Hervé
both are Maxwell.....
I am doing some more testing now...
Max, it is very hard to get shadows out of a small hdri, I guess not enough info...
Posted: Sat Jul 02, 2005 10:51 am
by Micha
Here a test image from a LDR last week. You mean shadows like here in the kitchen environment? Do you try a stronger Gamma? This should help.

Posted: Sat Jul 02, 2005 10:58 am
by Maximus3D
Mm yea i tried it all, they all looked flat to me. But i give it a new try today to see if i did something wrong, maybe i was just too tired late late last night.
/ Max
Posted: Sat Jul 02, 2005 11:17 am
by Hervé
OK, to help me and others...
the converted hdr >> MXI goes in emitter material shader of a sphere... right ?
OK, now where do U load the LDR to be seen on the sphere...
I tried in Color channel... no
I tried in Luminosity channel, yes it works, but I wonder if I do right ..?
Posted: Sat Jul 02, 2005 12:14 pm
by Hervé
I dunno, but there is somethig wrong here... I mean if I just map the MXI resulting from HDR>>> MXI convertion, and no maps in the luminosity channel, I get a bleck render, ... if I map the corresponding HDR in Luminosity channel, I get a black render, .... if I map nothing, but only level the slider, I get some lit in the render, but background is grey/white... If I map the LDR version of the HDR, I get a render, but luminosity slider has no effect (0% or 100,000,000%) I get always the same render....
If I play with the gamma and exposure during render, it shows by the way the image gets over-exposed (when you exagerate with exposure) that it gets brighter & brighter until over-exposed in almsot a linear way.. I mean if the sun is facing the camera, and the camera itself faces a wall, then the parts on each side of the walls just over-expose first, then the parts that are aginst the sun... but here it is not the case... am I clear or am crazy...
Posted: Sat Jul 02, 2005 12:19 pm
by Hervé
here are some renders... but does not look so good...

Posted: Sat Jul 02, 2005 12:23 pm
by Hervé
here are some F_Prime tests...

Posted: Sat Jul 02, 2005 12:29 pm
by Hervé
to finish with this... until we have some sort of tutorials... or fixind... dunno;...I dont say I am right or anything, but we need some tuts Tom..
the spherical mapping that looks like open GL... look on first page to see a Maxwell render...
here is the LW open GL screen shot..
