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ast issue, in part one of this series, we looked at

the five light types available in LightWave 3D

and explained how to set up a simple four-point

lighting rig. If you missed that part, dont worry:this instalment will continue our introduction to CG lighting

using techniques that can be applied in many programs.

Use this tutorial to discover the advanced lighting tools in

LightWaves Global Illumination panel, including Backdrop Only

radiosity, then set up a simple but effective lighting rig using image-

based lighting and a single, small Area light. In parts three and four,

oull make CG lights behave like real lights, and set up an indoor and

outdoor lighting environment.

First, an explanation of a key lighting term: radiosity. In the real

orld, all light bounces and reflects around the environment until its

absorbed. These reflections can occur hundreds, thousands or even

millions of times depending on the surface properties of the

environment. CG lights, on the other hand, do not reflect by default;

all of the light from CG sources is absorbed. This means that 3D

renderers need to deliberately calculate light-ray reflections.

In the old days, before radiosity was available as a rendering feature,

3D artists used to fake it, cleverly placing lighting instruments to

mimic the way light bounces. This trick is still used but is fast

becoming a lost art; as renderers and hardware become quickerand smarter, the need for fakes, tricks and hacks is diminishing.

Beautiful, more physically accurate lighting can now be produced

ith much less effort.

Be aware, though, that advanced lighting requires longer render

times. If your goal is photoreal effects or truly stunning renders, you

should accept this as a fact of successful CG lighting.

Start by opening LightWaveand loading up the scene named

3dw_LWLighting_part2.lws from the cover CD. Click on the Lights

mode button at the bottom of the interface, then hit the [P] key to

open the Light Properties panel. Youre now ready to begin.

Nicholas Boughen is CG Supervisor at Rainmaker in Vancouver.

His work includes Dead Like Meand I, Robot. He is the author

of LightWave 3D 8 Lighting, and training videos for KURV studios.

www.rainmaker.com

L

054 | D WORLD

3D ORLD December 2005

ACTFILE

In the second part of our guide to CG lighting, we take a look at the advanced lighting tools in LightWave 3D.Follow the walkthrough and create the dazzling set-up shown above BY NICHOLAS BOUGHENGet started in CG lightingPart 2LIGHTWAVE 3D

FOR

LightWave

DIFFICULTY

lementary

TIME TAKEN

30 minutes

Full-sized screenshots

ase model

(L ormat)

Start and finish

scene lesJ s used in the

scene files

ALSO REQUIRED

TUTORIALS |

OTHER ISSUES

Issue 70: Part 1Understanding real-world

lighting; basic CG light types

Issue 72: Part 3

Force CG lights to behave

exactly like real lights

Issue 73: Part 4

Lighting an interior scene

and an exterior scene

Subscribe today: page 44

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December 2005 WORLD

D WORLD | 055

t t e top o t e g t ropert e s pane , c c o a

Illumination (GI) to open the GI panel. From here you

an globally change Light Intensity, enable Lens

ares, o umetrc g ts, a ow aps an m ent

Intensity. You can manage the Ambient Colour settings and

enable either Radiosity or Caustics. Shading Noise Reduction

mproves g t ng qua ty or a osty an rea g ts.

01

n t e o a um nat on pane, set m ent

Intensity to 0%, turn on Shading Noise Reduction

nd enable Radiosity. Click in the drop-down box

next to ype an se ect ac rop n y rom t e st. eave

ll the other settings as they are.

02

ress tr + to open t e ac rop pt o ns. c

on the Gradient Backdrop box to add a generic Sky/

Ground gradient. This quick gradient is useful for

est ren ers. et ent o our to , , an y

Colour to 172, 225, 255. For more complex renders, click the

dd Environment bar at the bottom and Add Textured

nv ronment to nsert an mage or a custom gra ent.

03

STAGE ONE |Advanced lighting tools

et the Layer Type to Image Map. Set Projection to

y n r c a an t e exture x s to , t en c c on

he Image drop-down menu to load the image

background.jpg from the cover CD. You can leave all other

settngs n t e pane as t ey are.

06The first thing youll notice when rendering this

mage s t at t e g t coour s extreme y var e .

Because this light colour is taken from the image

hich is an outdoor photograph you can see highlights in

e ren er cause y cooure g t com ng rom many

irections. This effect is called image-based lighting and it

dds a brilliant level of detail.

07

Get started in CG lighting | TUTORIALS

Open the Backdrop panel again and turn off Gradient

Backdrop. Click on the Add Environment bar, then on

exture nvronment. ow c c exture

Environment, select the Y axis and click on Texture to open

up the Texture panel.

Click on the Lights mode button at the bottom of the

interface and then press the [P] key to open the

g t ropertes pane. e sure t at g t ntens ty

is set to 0% before continuing. Render the image by clicking

[F9]. Although the only light in the scene is turned off, the

scene s st um nate ecause we ave nstructe

LightWaveto emit illumination from the backdrop.

04 05

STAGE TWO |

EXPERT TIP

Types of radiosityBackdrop Only radiosity is like

Ambient Occlusion: no radiosity

bounces are calculated, but light is

emitted from the entire backdrop.

Its a great way to simulate skylight.

The backdrop does have to have

some colour in it, so set a colour, a

gradient or an image into the

backdrop. Monte Carlo radiosity willcalculate radiosity bounces, yet

takes longer to render; the more

bounces you add, the longer the

frame will take. Interpolated

radiosity enables you to shorten

render times by letting the renderer

guess the lighting values in a scene.

i

Open the Image Editor by typing [F6]. Select the

mage ca e ac groun . p g an c c t e ep a ce

button to replace it with white-square.jpg. As you

may expect, this is black with a white square in it. Wherever

t e mage s ac , no g t w e em t te rom t e a c rop;

wherever the image is white, light will be emitted. Now

render the frame.

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056 | 3D WORLD

3D WORLD December 2005

For the final image, pictured above, weve replaced

t e ac rop mage w t t e or g na ac groun

photo. This produces a good Ambient and Fill light

olution. We want the glasses to appear to be outside, so

e ve a s o a e an rea g t w t t e r g t s ze an

intensity to simulate sunlight. If you recall from part one of

his series last issue, the shadows should be quite hard-

edged with a little softness at their furthest point from the

g asses. oa t e scene w_ g t ng_part _ n s e . ws

to see the final set-up. You could easily switch the Backdrop

radiosity to Monte Carlo radiosity, to try out radiosity light

ounces. owever, w t t s o ect , muc o t e mater a s

quite dark and most of it is semi-transparent, so its unlikely

that youll see much difference.

12

TUTORIALS | Get started in CG lighting

ecause were creat ng a g t ng r g v a mage-

based lighting, we have specifically placed and

coloured the squares so they would match

t e pos t on an coour o g t ng nstruments. eres one

main disadvantage to this system: since theres only one

Radiosity Intensity value, all lights in the scene will have the

same eve o ntens ty uness t e o our vaue s care u y

adjusted for each square.

10

STAGE TWO (Continued) |Image-based lighting

ress to ren er. otce t at t e t e oor seems

uite blue. This is because it has Reflectivity turned

on, an n a t o n to e ng um n ate y t e ue

s e, t s s a so re ectng t at co our. ere are am er

highlights along the tile edges, and if you look closely, youll

see two s a ows: one occ u e rom t e ue s e an one

from the amber side, indicating two distinct light sources.

11

EXPERT TIP

Animating coloursThere are many different ways to

illuminate your scene using Backdrop

Only radiosity. In this tutorial, we

used a simple gradient backdrop,

but you have the option of using

anything that can be put in a Texture

panel, including photographs, HDRI,

procedural textures, plain colours or

custom gradients. You can even

animate these over time if you wish.

For example, you may want to

produce a time-lapse of the sun

rising or setting, or of a vehicle

driving past in the night. You could

also simulate a nuclear blast in the

distance the options are endless.

i

ote ow muc t s tec n q ue m m cs t e use o a

ingle, large Area light in the scene. You can see

learly that the light source comes from the left of

t e rame t s s w ere t e w te port o n o t e m age

exists in the backdrop. Lets try adding some colour now.

Using the Image Editor again, replace the image named

w te-square. pg w t co oure - g t. pg.

09

EXPERT TIP

Two techniquesThis tutorial demonstrates theversatility of image-based lighting.

Whether you use photos in the

backdrop or hand-drawn images, you

have specific control over how the

image illuminates your scene. For

most everyday purposes, this

technique may take too long to

render if you dont have access to a

render farm, so mix image-based

lighting with instrument lighting.

Its useful to choose an appropriate

backdrop image for your Fill lightsource and provide a more direct

light source through a Spot light,

Area light or Distant light.

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