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colour mapping the human and and photography
show user profile  zeefusion
I am trying to come up with a answer that best describes how humans see colour and how a camera sees colour.

For example, and I may not be correct because this is why I am asking. The human eye sees everything as linear?

If you attempt to replicate a linear environment in 3d, in some situations the lights can appear blown out. This is because 3ds max renders through a camera not the human eye. To correct this you can apply an exponential colour mapping so that it brings everything back to how we think it should be.

Do cameras use exponential or something else?

Thanks
read 1153 times
6/7/2011 7:02:28 PM (last edit: 6/7/2011 7:02:28 PM)
show user profile  Error404
I do know your mind has alot to do with it, filling in gaps and making things look different. As far as what sort of 'curve' your eye sees a linear ramp of value as, I have no idea.

Just a for instance, when I'm hiking out near the ocean after the sun has just dipped down below the horizon, the water usually looks noticeably brighter than the sky just above the horizon, as if the water were reflecting brighter than the sky. But just for sanity sake, take a photograph and it's clearly not the case, the sky is much brighter. And then the old trick of the grey dot on a white surface and a darker grey surface, your eyes/mind make the identical grey dots look like quite a different value depending on their surrounding values, even though they are the same.

Your eyes/mind do alot of cool and funky things. Same thing with motion and with sound as well. If you see someone's lips mouthing something different than what you are hearing, in some cases you will "hear" what the lips are mouthing, and not the actual audio that is being played.

www.DanielBuck.net - www.DNSFail.com

read 1126 times
6/8/2011 11:43:34 AM (last edit: 6/8/2011 11:45:52 AM)
show user profile  Nik Clark
Your mind does a lot of the work, As 404 Daniel said. Look at the following mind blowing image.

The green and blue are the same color. Amazing.



read 1117 times
6/8/2011 11:58:39 AM (last edit: 6/8/2011 11:58:39 AM)
show user profile  zeefusion
I see green and pink :/
read 1108 times
6/8/2011 12:16:26 PM (last edit: 6/8/2011 12:16:26 PM)
show user profile  zeefusion
I have been reading thishttp://robertokoci.com/advanced-vray-materials/


here is what they said "One important thing: set the color mapping type to exponential as it is the way that things work in nature."

I am now confused about what is correct for rendering what we see, linear or exponential?

I assume linear is correct but may return un-desirable results because 3ds Max renders through a camera, there for exponential is a much better match to what we expect to see.
read 1100 times
6/8/2011 12:37:45 PM (last edit: 6/8/2011 12:37:45 PM)
show user profile  Mr_Stabby
the dynamic range of an average photograph or a computer screen is about 1/100000th of what human eye can perceive, obviously a lot of fiddling is required to push anything useful into a medium that tiny but worry not! this has all been figured out and all you really need to know about it is

the dynamic range of the whatever you are capturing is defined by exposure value
the dynamic range of the capturing medium is defined by how many bits per pixel you are willing to spend on it

so basically the more different levels of light you need to squeeze in your medium the smaller exposure(=bigger EV) you need, now here comes the tricky part - the perceived dynamic range following highest level of light relates exponentially to its lower level counterparts.. this is difficult for me to put into english but ill make up an example - lets say there are 2 lightbulbs and a torch in a dark room, 1 lightbulb is twice as powerful as the other one and both of the lightbulbs are brighter then the torch. Now if you take a picture and adjust your exposure to carry the full dynamic range of the weaker lightbulb you get a ratio of how much more powerful the weaker lightbulb is then the torch but if you take a picture and adjust your exposure to carry the dynamic range of the more powerful lightbulb with the weaker lightbulb still in the picture you get a new ratio between the weaker lightbulb and the torch and it is exponentially smaller. This sounded better in my head...

anyway all that you should be concerned with is choosing the correct amount of light to illuminate the scene because materials reflect/absorb light in different quantities relative to their intensity (alltho im unaware if 3d renderers actually take this into account because the differences are extremely tiny in most practical cases) and the exposure to capture the full range of luminance you will be sticking into your medium

read 1079 times
6/8/2011 4:41:05 PM (last edit: 6/8/2011 4:58:43 PM)
show user profile  zeefusion
So............. it doesn't matter what colour mapping you choose? They are all correct? If so, then why do people bang on about using linear colour mapping all the time?

I have always used exponential because that's what I was taught. I then started using Linear because that's what people say you should use because that's how things work.

Now my results are very blown out, so I read on and find out that exponential is far more realistic to how we as humans see things.

I'm now like grrrrrrrrrrrrrrrrrrrrrrrrrrrrr!
read 1066 times
6/8/2011 5:03:36 PM (last edit: 6/8/2011 5:03:36 PM)
show user profile  Mr_Stabby
oh im just talking about how light appears not what setting to pick, i have no experience with vray or any of its weirdness

read 1059 times
6/8/2011 5:24:01 PM (last edit: 6/8/2011 5:24:01 PM)
show user profile  zeefusion
I thought it was the same for all renderers? How does MR deal with this? Is it just Vray then that has made it complicated? Does MR just render linearly or something?
read 1056 times
6/8/2011 5:26:58 PM (last edit: 6/8/2011 5:26:58 PM)
show user profile  Mr_Stabby
linearly? as in linear color space output? thats a whole other topic and not dependent on renderer at all, linear luminance output? that would be just silly why would anybody do that. Linear input? irrelevant, numbers dont care how people see things

basically there is no such option in mr, i havent got the slightest clue what ur talking about

read 1043 times
6/8/2011 5:55:23 PM (last edit: 6/8/2011 5:55:23 PM)
show user profile  zeefusion
I'm just trying get my head around it all. Vray users suggest rendering using linear colour mapping and saving out as gamma 1.0 so that everything is linear.

But others render using other colour mapping methods such as exponential and state that this is a more natural method. I assumed these were common terminologies that are used in all 3d rendering applications. But from your response it doesn't seem so.

Only reason why I am confused is because a guy said "One important thing: set the color mapping type to exponential as it is the way that things work in nature."

So I assumed exponential colour mapping is a common thing. Which went against what I thought was correct that everything is linear.

Maybe I am getting mixed up but its because I am trying to understand why there are various explanations stating different things. I wanted to find out what is the "correct" method for rendering through a camera.
read 1036 times
6/8/2011 6:03:42 PM (last edit: 6/8/2011 6:07:41 PM)
show user profile  cadmonkey33
if you're using lwf, you're supposed to use linear. thats the point of lwf.

if not, you can use one of the other options, exponential, hsv exponential, reinhard etc.
ppl who dont use lwf tend to like exponential coz it tames your blowouts.
some also like reinhard for the same reason.
hsv exponential restores some of the colour you can lose in your highlights with exponential.

but really, its a matter of taste. anyone you ask will have their own opinion. thats why you get conflicting advice on forums.


Nat Saiger.
Portfolio

read 1024 times
6/8/2011 6:25:36 PM (last edit: 6/8/2011 6:25:36 PM)
show user profile  BishBashRoss
I believe if you want to use proper LWF then linear multiply is required. Otherwise you can try the other options depending on the look you are after.

Edit.

Damn you CAD Monkey! ;)





read 1023 times
6/8/2011 6:26:57 PM (last edit: 6/8/2011 6:33:37 PM)
show user profile  albongino
Here we go again!
You could break it down into 2 options: 1 to simulate what the eye sees, 2 - to simulate what a camera sees.

For the eye simulation option:
Since the eye can adjust to a given light situation in a way a camera wouldn't, then there are no blown areas in the image (Exponential). So you adjust the lights in the scene to give an appealing look throughout the image, while trying to keep as much contrast as you can, (this method is I think the most popular)

For the camera simulation option:
you focus only on a subject in the image and depending on the light intensity on your focus area with relation to your light sources, there will be blown out/ overexposed areas or the contrary. (Linear/gamma 2.2), in this situation you are playing with an image just like a real photographer / cinematographer would in reality.

as per which is the best way to go? I guess you just try to find your own recipe, just like everybody else, either by combining techniques or bending "rules", the important thing is to get a decent image out of it.

................



read 1009 times
6/8/2011 7:01:35 PM (last edit: 6/8/2011 7:01:35 PM)
show user profile  zeefusion
Thanks albongino, that's exactly what I wanted to hear :)
read 1006 times
6/8/2011 7:32:51 PM (last edit: 6/8/2011 7:33:00 PM)
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