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BryceTalk Skies
July 22, 1999
Part 3 of 5
1 2 3 4 5

BryceTalk Skies, July 22, 1999
Part 3

Meta AuntiAlias: Reflash, go ahead!

Reflash: If I change the sun color, to say red

Reflash: the entire scene gets a red filter over it

Reflash: but I only want red light...not the red over everything

ideas??

Dr. Mojo: Sounds like you need more than one light.

Sky Pilot: That's your biggest light source

Dr. Mojo: If the sun turned red, so would everything you saw...

Wolfie: Thing of shining a red flashlight at night in your room..everything is going to look red.

Reflash: it doesnt look natureal

you can actually see the red added like a veil pulled over the scene

Dr. Mojo: That's what would happen in Nature!

Sky Pilot: I think so too

Wolfie: yes

Sky Pilot: Haven't seen a red sun yet

Reflash: amybe im living in unreality :)

stiffkat: reflash, have you tried using spots or large sphere lights?

lars: Yes. if the sun turned red in nature. We would all die and everything would look red.

norm: Example: Darkroom!

stiffkat: for local color

Dr. Mojo: The human brain adjusts v. rapidly to the color of ambient light. That may be why it looks wrong. You're in a room w/o the same red light.

Reflash: i will try spots, etc...thanks

if you watch

Clay: !

Reflash: a sunset, when the sun is bright red

Dr. Mojo: That is, only your picture is red, not your entire environment.

lars: flash are you just trying to turn one thing red.

stiffkat: ?

Meta AuntiAlias: Reflash, I'm working on an explanation for you that sorta covers a few things. Will paste it in here when I finish with it.

John_Spirko: At sunrise and sunset, due to the atmosphere, the sun can appear to be red, without coloring everthing red.

Meta AuntiAlias: Clay, go ahead!

Dr. Mojo: The sky is still v. blue in a sunset in Nature.

Clay: I have a neat little tip for cloud planes, it makes water look a little more real, if anyone is interested:-)

Reflash: ok, thsanks aunti..next

Sky Pilot: Is it something you could do with specular color on objects?

FSUGary: how's the queue lookin?

Dr. Mojo: Hmm. Dunno...

Wolfie: or possibly tinting the "ambiant" color of an object's material

Clay: nevermind go ahead

Sky Pilot: The red thing

that too

Heather: What was Clay's tip?

Dr. Mojo: Make ambient blue; that might help...

Sky Pilot: but will be all over

Meta AuntiAlias: stiffkat has a question...

Clay: (don't want to cause confusion)

Yojimbo: ;)

stiffkat: Mo, I got booted and missed part of this tonight, can you tell me if I add presets to clouds in the DTE should I stick to greyscale or do you have any tips about that?

Dr. Mojo: Color does not come through, so it makes no diff. what you do in the DTE.

Dr. Mojo: (colorwise)

stiffkat: ah, that helps :)

Meta AuntiAlias: yeah, color for clouds in DTE is fine :)

Dr. Mojo: Yes, it's strange...

Wolfie: So color in dte has no bearing on the cloud layer?

Only bump and alpha?

Dr. Mojo: Auntie, is it the cloud color in the Sky Lab that is irrelevant?

stiffkat: I want to experiment with some KPT 5 output and figured I'd need to go greyscale...

Sky Pilot: On the cloud tab

Sky Pilot: I think those colors are for contrast

Dr. Mojo: You know, I just don't remember exactly what the deal is. I know the colors in the Cloud tab in the SL are irrelevant.

Sky Pilot: To help you see them

Meta AuntiAlias: okay... I got some comments re: earlier question re: red sun...

Sky Pilot: M-kay

Meta AuntiAlias: oh, we're still on DTE and colros?

Wolfie: only for show in SL? Not applied to cloud texture then right?

Yojimbo: yes it's just Alpha levels as far as the color goes

stiffkat: done Aunti, thanks

Meta AuntiAlias: the color that you see, yes, is irrelevant. Has more to do with what Bryce does to any texture to display its likeness...

Sky doesn't USE any color information, usues only Alpha (or value)

but.. you'll still see the "likeness" of color for display

Dr. Mojo: That's the starnge part...

And I mean "starnge," not "strange!"

Steve Lareau: <whispering> Yojimbo- meet me in the lobby for a sec...

Meta AuntiAlias: may I take amoment to discuss Sun Color/Ambient Color and Materials: Diffuse Color and Ambient color?

You have lots of things to affect the color of something in sunlight.

First, you have the color of the object itself.

Some colors in Materials. That's for the object

orbit: please do

Meta AuntiAlias: materials: Diffuse and Ambient Color...

Diffuse color is what color object is when sunlight (or direct light) hits it.

Ambient color is all over color, and is seen more obviously when in shadow.

And both those things (we're talking materials here, still) are affected by Diffusion Amount and Ambience Amount. (whew!)

Now, in Sky& Fog, the Sun color is the color of the direct light as it hits that object.

.

So white object lit by red sun will look red where the sunlight hits it.

Dr. Mojo: <More accurately, "diffuse" is the reflection of an ideal Lambertion (diffuse) reflector.>

Meta AuntiAlias: And, there is Ambient color for sky, which is an all-over color, but is also more apparent in shadow.

(what he said!)

when it comes to creating your final appearance of object in scene and mixing colors....

Sun color is tied to Diffuse Color. The two of them will mix

Sky Ambient Color is tied to Ambient Color in Materials. They two will mix.

And Ambient Color (both) will affect overall appearnce of scene

Dr. Mojo: <Ambient accounts for multiply scattered, indirect light in a particulary poor approximation.>

Sky Pilot: Where the red gets all over is because Bryce sees it reflecting off other objets

stiffkat: I get it now!!

Meta AuntiAlias: clarify, Sky Pilot... we're talking red sunlight color

Sky Pilot: Back to orig ?

stiffkat: That's what I was trying for, how to mix them to achieve final output

Meta AuntiAlias: so.. in practical ways, those are the colors to play with...

Dr. Mojo: <What I sometimes do is subtract the ambient color & brightness from the sunlight, for an overall white sunlight. I use blue ambient and yellow sunlight.>

Wolfie: Is there any cross polination? Sun color to ambiant material color and vice versa?

Meta AuntiAlias: yes, there is....

Dr. Mojo: They get added up. Simple.

Meta AuntiAlias: same way as that weird light turns your lips blue

Sky Pilot: All goes into the equation

Meta AuntiAlias: lip color = diffuse color (material)

Dr. Mojo: (Where the sun illuminates. Ambient only, in shadow.)

Meta AuntiAlias: weird light = sunlight

the color combination is funky, or at least, that's what your eyes tell me! : )

Wolfie: oh...that is what that thing is up there?

Meta AuntiAlias: er.. my eyes tell me

Wolfie: I saw it once!

camel: You mean that round thing?

Yojimbo: lol

Clay: LOL

Yojimbo: Is that still out there?

Dr. Mojo: "On the big screen they showed us the sun..."

stiffkat: lol Mo

Dr. Mojo: Can you name the song?

Meta AuntiAlias: er.. by weird light = sunlight, I meant that the funky light (mercury light? I forgot.. it's the kind that turns your lips blue) shines.. the principle is similar to choosing light color in Sky and Fog...

Sky Pilot: Good example

stiffkat: pffffffft, no, heard it, can't name it

3d~?~elf: wierd al yank o switch?

Dr. Mojo: Elton John, "Grey Seal," Yellow Brick Road.

Meta AuntiAlias: so, ergo.. weird light = Sun (i.e., Bryce sun color) color

orbit: enjoyed this but will have to digest the rest 4:30 on the east coast isnt that far away night all

Sky Pilot: Those merc vapor lights don't do complete spectrum

Dr. Mojo: Look at 'em through a prism or diffraction grating sometime!

stiffkat: aaargh, I have that album too, my alzheimer's is at work ;P

Meta AuntiAlias: so... of course, in addition to the 2 already mentioned, Bryce sun color, Ambient color (sky) there's also Haze... and the Haze color......

Meta AuntiAlias: that also affects the appearnce of color in your scene....

Dr. Mojo: Fog, too.

Wolfie: By wierd light you mean mercury vapor light?

Meta AuntiAlias: ::::getting ready to pass the ball off to Dr. Mojo F. Kenton Musgrave::::::

stiffkat: yep, but haze and fog make decent sense to me.......for now anyway

Dr. Mojo: Ready...

Meta AuntiAlias: before we turn to a NEW feature in Bryce 4, Color Perspective.....

Dr. Mojo: You want strange color, I got it:

Meta AuntiAlias: any last questions/need for clarification on Ambient Color in Bryce Sky? or SUnlight Color?

stiffkat: I'm clear

Meta AuntiAlias: else hold your peace. and Ken'll tell all! : )

camel: LOL!!

Wolfie: got cloud ?

Clay: heheh

Dr. Mojo: Yeah, at the end!

Meta AuntiAlias: anytime you wanna direct 'em to the movie, Ken, let me know, and I'll shout out da URL

: )

Dr. Mojo: I have it in the prepared spiel--your cue awaits!

Yojimbo: ahh the tension mounts

Dr. Mojo: Okay, here we go:

I want to bring your attention to color perspective: a cool and important feature in B4's Sky Lab. I'll try to explain what it is and how it works. Please put on your thinking caps and bear with me--this is highly non-obvious and non-intuitive.

Aerial perspective, of which color perspective is a part, has been known by landscape painters for hundreds of years to be the primary visual cue indicating truly large scale. Leonardo wrote about it; it appears in the landscape behind the Mona Lisa.

Meta AuntiAlias: :::dons thinking cap:::::

Sky Pilot: But cool!!

Dr. Mojo: Without it, things cannot b emade to look really big!

Wolfie: ^

Dr. Mojo: For a little writeup on aerial perspective and the color perspective research that led up to the B4 feature, see http://www.wizardnet.com/musgrave/4_persp.html (there are cool illustrations there, too).

Sky Pilot: lol wolfie!

Dr. Mojo: (Let's see if we can crash wizardnet.com)

Aerial perspective has two parts: atmospheric perspective and color perspective. The former is simply the loss in contrast with distance that a grey mist can provide. The latter is the shift in color with distance, which is far more subtle.

The way they both work is this: First we get the color at the end of a ray, as when it hits a surface. Next we take the atmospheric color and partially substitute it in for the first, distant color, as a function of distance.

The greater the distance, the more atmosphere color is substituted in for the distance color. Altitude can also be a factor, as with Bryce's "fog," which is denser down low than up high.

So really close surfaces get virtually no atmospheric contribution, while really distant surfaces aren't seen at all--only the color of the atmosphere is seen. Both Bryce's "fog" and "mist" work this way.

Clay: neat quicky page mojo

Dr. Mojo: Glad you like it!

Dr. Mojo: Color perspective is the change of colors with distance due to the atmosphere. Dark areas turn blue and light areas yellow, then orange, then red, with distance (for the same reasons the sky is blue and sunsets are red--too complicated to go into here).

Sky Pilot: Heavy stuff

More realism!

Dr. Mojo: Indeed!

The controls for color perspective (CP) determine the rate at which the distant color is replaced with the color of the atmosphere for each of r, g and b, SEPARATELY. It's kinda bizarre and non-intuitive, but it IS that simple! "Trust me." >;^)

It turns out that to get white to turn red and black to turn blue (as we see in Susan's and my spiffy animation--Susan?) you need to start with a neutral grey atmosphere color, or something close to it. Too dark or light, and you lose one effect.

Wolfie: refraction and color absorption

Meta AuntiAlias: hang on.. will post url

http://www.metacreations.com/products/bryce4/talk/events.cfm

scroll down to today's date, and there's a linnk to an animation... : )

Yojimbo: ?

Dr. Mojo: It has some really bizarre effects in Nature. It is why the sky is blue and sunsets are red.

Wolfie: doesn't work susan

Meta AuntiAlias: or is slow (been some server problems today)

Dr. Mojo: D'oh! Glad I'm not the only one with troubles in posting!

Meta AuntiAlias: hang on a sec...

Yojimbo: I'm getting it

Meta AuntiAlias: taken a while to fill in.. is it happening?

Wolfie: this is the link: http://www.metacreations.com/products/bryce4/talk/events.cfm#

Dr. Mojo: For a gratuitous animation, see:

Meta AuntiAlias: er no

Dr. Mojo: http://www.wizardnet.com/musgrave/Sunrise.avi

Wolfie: much better

Dr. Mojo: Only the CP changes in that animation.

Yojimbo: Question regarding the Neutral grey?

Meta AuntiAlias: http://www.metacreations.com/products/bryce4/talk/movie_cp.cfm

Dr. Mojo: (Both animations, actually.)

Wolfie: are they the same?

Dr. Mojo: NO.

Sky Pilot: Animating a sky attribute

stiffkat: loading here........

Sky Pilot: cool!

Dr. Mojo: I'll post the scene file for mine sometime...hopefully "soon."

Wolfie: <-loading Mojo Movie

Meta AuntiAlias: Wolfie.. both the same where? Mojo's link or the link I gave you?

Wolfie: yes

Dr. Mojo: I also have a huge animation of a sunset done in a developmental version of Bryce. Not ready for real time, but someday. It's a sunset, done right. But don't all try to download it at once, please!

http://www.wizardnet.com/musgrave/Sunset.avi

Wolfie: sorry...already am

er I mean did

stiffkat: I'll go later Mo :)

norm: Sunrise: 24%..... . . . . . .

Yojimbo: ?

Wolfie: damn...it gpf'd netscape

Meta AuntiAlias: Ken, you want to say anything about the gray to color movie/anim that we did while the sunset.avi is downloading?

Dr. Mojo: I meant the sunset, not the sunrise--it's much bigger. And a completely different model. It's just a tease, alas...

Susan's and my animation shows the realistic use of CP. You should study the scene file and steal some of the settings.

Yojimbo: hehe

Meta AuntiAlias: wow.. I just noticed this about the movie we did with the pyramids... the higher the color perspective gets, the further forward the color advances......

Sky Pilot: That's a big help

Dr. Mojo: They get rather extreme near the end. But they are very realistic (for Earth's atmosphere).

Sky Pilot: Thanks!

Yojimbo: first time I heard "Steel" as a should do thing

Sky Pilot: Right

Dr. Mojo: Yeah, well, I'm an anarchist at heart...

Meta AuntiAlias: Let me know if the scene files don't load up properly or anything! didn't do complete tests of them!

Yojimbo: lol

DaleP: OK

CBXTX: ?

camel: Works for me!!!

Meta AuntiAlias: i.e., of compressing, hqx, upload, download, unhqx and un-compressing

stiffkat: cracking open scene files is a great way to learn :)

Dr. Mojo: I know this doesn't immediately make sense, but experiment with CP. You can get some truly bizarre effects, as well as unprecedented realism. Look forward to some tutorials on how to get certain effects. EXPERIMENT--you can create great moods with CP!

Yojimbo: What's the value for neutral grey?

Meta AuntiAlias: very valuable, when it comes to CP!

Dr. Mojo: Like, 0.5, 0.5, 0.5

Meta AuntiAlias: ; )

Yojimbo: ahh

thanks

Meta AuntiAlias: or in this case, 15 15 15

Sky Pilot: Great for underwater, right Ken?

Yojimbo: right

>>>> Next up: Ken's "cloud tease" (and what a tease!)

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