lighting 3D interiors

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Basics of simulating interior lighting

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Download and install my Room Model into Vue 3D, if you're a Vue modeler and want to follow through with your own experiments using my info. It's populated with all the props and was made in Vue 5 Infinite as a .VOB file of 6.9MB, in a ZIP file.

Room Model notes

To keep all props in place I had to "Group" everything. To do that, I needed to move all light sources to a separate layer in the object list. You might want to "Ungroup" things (right click on an object) and move the light sources back into their objects. This is only in the objects list. All light sources are still properly located inside the model room.

Interior lighting introduction

Interiors, almost by definition, have surfaces near each other. In the real world this means that light is reflected from all but the darkest surfaces and it then illuminates nearby surfaces, which may also reflect in their turn and light even more surfaces.

This scattered light usually builds up to something like a rough equivalent of adding another (dim) light source into the environment. It's called "ambient light" and is very much like the ambient sound field that builds up in most indoor environments from multiple reflections of sound energy.

But simply adding some light everywhere in an indoor scene, to mimic ambient light, doesn't look very realistic. And if you make it bright enough to compensate for the lack of sunlight in most rooms, you loose too much contrast (dynamic range). This state of affairs tends to lead to dark, washed out indoor scenes, when your only simulated light source is sunlight through windows or such.

Happily, we can bring Radiosity to the rescue. Radiosity lighting calculations are fairly new and not available in all computer graphics programs. They are the only type of lighting calculation which accurately simulates indirect light reflections from surfaces.

At the cost of long render times, Radiosity can simulate natural looking interiors.

Understanding interiors and indirect lighting

When light hits an opaque surface, it is either absorbed (converted into a bit of heat) or reflected - but usually a bit of both. Since most surfaces are not such great mirrors, this reflected light is usually scattered in many directions, which gradually dissipates it.

However, this reflected light will light up nearby surfaces and the nearer the surface the brighter. Of course, colored surfaces will also color the light they reflect and add that color to nearby surfaces.

All of this indirectly reflected light is called "ambient" light to distinguish it from the light that comes directly from a light source without any reflections and is therefore considerably brighter.

These days, most room surfaces are painted in light or white colors to use this behavior of light to increase the level of illumination in rooms, without requiring as much window space or as many artificial light sources. Windows add cost and leak heat or cold, while extra light sources also add to building cost, put out excess heat and consume expensive energy.

Most methods of calculating the lighting in a 3D computer graphics scene can't deal with the indirect light reflections from one surface to another. They fake it by just adding light everywhere in a room, to represent the ambient light - but this is unrealistic, and it shows.

The relatively new "Radiosity" type of lighting calculation does accurately simulate indirect light reflections - so it is the key to natural looking interior scenes in Vue 5i.

Radiosity to the Rescue!

To demonstrate interior lighting with Radiosity, i built a 3D model room. It has white walls and ceiling and a wood floor and is completely light-tight, except for a large window (no glass) and a small skylight (no glass). This is what it looks like.

A simple 3D room model for interior lighting experiments.

Standard Render

Here is what a Global Illumination type of lighting calculation looks like in this room. There are 2 light sources. The sun is shining through the skylight and the window. And an invisible Point Light is placed just inside the window. You can see that even with this extra light source, standard illumination is not a very good solution. Of course, i could turn that point source way up in level, but that would lower the scene contrast and overpower the sunlight coming through the openings.

Dissapointing standard render of room interior.

Radiosity Render

Without changing other settings, we turn on Radiosity and render again
(sorry, had to switch trees on you).

A big improvement!

But what if we turn off that point source? Just how much does this Radiosity help with only the outside sun?

I like it! Of course it takes even longer to render.

To make comparison a bit easier, i cut strips from each render. Which do you like?

There are brightness differences that make it a bit hard to compare, but if you look at the edges, corners and undersides of the room surfaces, i think you can reach some conclusions. Personally, i like the top render, but maybe with a bit more Radiosity gain.

Those Devilish Details

Here is a short summary of light settings and methods, but first an important note:
These settings are the correct ones to get the effect i want, as far as my current understanding of Vue Infinite goes. But they were not meant for maximum render quality. They are set for medium quality and minimum render time.

Also, Vue Radiosity will continue to imrove in the future and new setting will become available - so be sure to keep up to date by reading the manual.

Several of the quality settings should be boosted, if you want better quality. In other words, you don't have to change which settings are used, but you could very well increase the numbers which affect quality.

Atmosphere Editor > Light:
Settings apply to all lights

Gain: 0.10 (strength of Radiosity - but amount of ambient seems a stronger effect)
Quality Boost: +2.5 (combines several settings you can't see into one easier one)
Light Intensity: +1.10 (overall scene brightness)
Ambient: 60% Ambient, 40% Sun (ambient light Vs sunlight - Radiosity needs considerable ambient - but not too much!)

Sky dome Gain: +1.0(Similar to boost in Ambient Vs Sunlight, increases skylight)

Light & Shadow Settings:
Shadows: 60%
Invisible: (i.e. lens flares off)

Point Light:
Invisible: (i.e. lens flares off)
Shadows: Disabled

1. Use Radiosity for indirect surface reflections
2. Walls and ceiling are white to better reflect light
3. Boost sunlight, to get more light energy into the room - including sky dome
4. Add point light and place it near window to avoid hot spots and improve realism
5. Skylight above planter provides more light, especially onto tree

Unused possibilities:
1. Could have also boosted default brightness of wall/ceiling material in Material Editor > Effects

2. Could have set Global Radiosity > Indirect lighting. Better quality + long render.

Vue 5 Infinite Settings Details:

Time to show those screen shots of important settings.

First, the Light settings in the Atmosphere Editor:

Now the render settings (1 of 3):

(2 of 3)

(3 of 3)

Please be sure to read the extensive information in the "Help" files for the light settings and for the render settings - it really is critical to understanding Vue.

~ End ~


Wishing you a creative future!
   _jim coe
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