The Atmosphere Editor in Depth

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Michel Rondberg's picture
Michel Rondberg
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Joined: Feb 12 2011

This article is currently being written, is subject to change, and  may be incomplete,content is saved while working on the article

ROUGH DRAFT, MAY CONTAIN TYP'O'S BAD GRAMMER AND MISTAKES

VERSION 0.1

PART 1: Lighting Models


The Light Tab

Before we talk about the different lighting models, lets quickly look at the Global lightin adjustment sliders 
THe Light intensity slider simply makes the light darker or brighter. The light balance slider set the ratio between
ambient light and direct sunlight. The ambient light ratio slider, lets you choose between uniform (The ambient color
you are defining, or from the sky (For nature scene we want this set at 100%, this is how the earth is lit by the sun. 
OFor an overcast day you can then set the light balance slider around 50% for a mix between ambient light and sunligt. 
For a bright summer day with little to no clouds one would put this more towarrds sunlight.

Lets look at ambient light. We will set the intensity to 0, light balance fully to ambient, and ambient light fully to from sky. This allows
us to look at the different lighting models and how they provide ambient light, (The way ambient light is generated in Vue)


The first model is the standard model, and is obselete. The ambient light color comes from the color you define in the ambient light color tab. This model is obsolete and there is no reason to use this at all.

Standard model:



The next model is GA, short for Global Ambience GA will grab the ambient color from the sky and use that as a form of highlighting.

Shown in this render:



You can see we have no contrasted shadows, so this mode is considered obselete.

Next we have AO and GI. These are basicly the same, only witht he AO model you can set the distance for the occlusion The skydome will lit the scene, and the GI engine will determine which parts of the object get skydome lighing or not. (occluded)

AO:




GI:



Finnaly we have GR, or Global Radiosity. This is the most realistic lighting model, and also the most expensive in in terms of rendertime. However it is  far superior to all other models. In this article we will only focus on GR.

GR:


GR, is another way to calculate GI, not only we get skylight, but Vue also calculated light reflecting from object in the scene and cast that onto other object. This will create color bleeding. Notice in the render above, how the red sphere, reflects its red color on the ground nearby. The blue sphere reflects some blue light into the shadow of the spheres. This is what happens in real life.

For this to work, light balance slider must be towards sunlight. A good value to try out is   80  to 99.
The gain, is used to boost the reflected light from object from below. The SDLG (Sky Dome Lighting Gain) will boost the light coming from the skydome litting the scene from above. To use SDLG  your light balance must be set near the sun. For high SDLG values like 6, you need atleast 90% sunlight balance.

The  checkbox "optimized  for outdoor rendering" is what should be used for outdoor scenes. Vue will limit the amount of photons being send, since the scene is infinite. This makes processing your nature outdoor scene faster. Untick this for indoor scenes. Reflected light will be much stronger and increased photons are used, since the area these photons can bounce in, is  confined to a small area like a living room,, or house.

Indirect atmospheres: This is cloud radiosity, we will talk about this later on.

Indirect skylighting: Indirect lighting from the sky will be calculated. (Each tiny dot int he sky is esentally a light source in Vue)
 

Michel Rondberg's picture
Michel Rondberg
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Joined: Feb 12 2011
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Michel Rondberg's picture
Michel Rondberg
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Joined: Feb 12 2011
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Michel Rondberg's picture
Michel Rondberg
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KenM (not verified)
See- I learned a lot :) Thanks :)
ClintH's picture
ClintH
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Joined: Oct 24 2010
I agree. Good information for sure.
Thanks for charing that Michel!
Michel Rondberg's picture
Michel Rondberg
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Joined: Feb 12 2011
Hey guys, I will be expanding this in much more detail, just 1001 things to do, and right now its 35 degrees , my a/c can hardly cope. Once the weather cools down a bit (and so my head) I will continue, stay tuned!! 
Drea's picture
Drea
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Joined: May 3 2011
same here... ;)
ClintH's picture
ClintH
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Joined: Oct 24 2010
Awesome news you guys!
I so want to bump up my Vue skills - both of you produce work that inspires me on a daily basis..thank you for that!
Szark's picture
Szark
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Joined: Jan 7 2011

I would love to see this finsihed one day. ;) I am been getting to this point through trial and error and even then this was a great help.