3D Lighting Note

Lighting I
What is light?
Types of lights in Maya
Light properties and controls
3-point lighting
Framing your shot
Light linking

1. What is light?
This is an ancient question, something we encounter everyday from the moment we open our eyes, from the first moment weÕre born.
The essence of light is that it is a form of energy. Being a form of energy means that it follows one of the major laws of physics, mainly the law of conservation of energy. This law states that energy is never created nor destroyed. Energy is converted from one form to another.

Physics has two models to describe the behavior of light. There is the wave model and the particle model. They are both equally valid, and the details are not too important in our treatment of light, although for our purposes the particle model is the predominant model used in computer graphics.

Light decay
Color of light
Diffuse and specular
Kelvin scale
Light travels in parallel rays in the particle model


for class 2/12/08

3 point lighting

The visual function of shadows
define spacial relationships

reveal alternate angles - profile of character

enhancing composition

adding contrast

indicating off screen space - cookies

Integrating elements

Which lights needs shadows
shadow clutter

secondary shadows

Shadow color

testing shadows

Shadow size and perspective

Shadow algorithms
depth map shadows
resolution and memory use
depth map framing -- look through camera -- light with big cone angle poor shadow map, tight angle, tight shadow

Depth map bias and self-shadow artifact
banding pattern, increase/raise bias to remove banding artifact
fixing light leeks with bias set too high

transperancy support

raytrace shadows
how raytrace shadow work
trace depth

hard and soft shadows

hard and soft light
soft shadows with depth maps
array of lights
light dome

soft raytraced shadows
area lights
light radius
mimic area light

turn up shadow samples or shadow rays to soften noise


UV mapping
specifics for next weeks assignment:
- your scene must have camera that you render through, that is not the perspective camera (or any orhtographic cameras).
- That camera must be locked in place for your renders (I should be able to open up your scene, hit the render button, and get relatively the same render as what you turn in)
- size should be 1024x1024 (1K square in the presets of the render globals)
- light 3 different times of day or weather situation (cloudy/overcast, in a room at dusk, outside in a picnic, etc)
- don't be afraid of moving things around, but keep all the elements in there.
- all surfaces should be a assigned a shader/material other than the default Lambert
- Don't be afraid to rebuild or crate substitute geometry (The orange for instance).
- At the beginning of class I will inform you that I'm about to download files from the server. If you're maya project and renders are not in there, clearly labeled, it will be counted as late.

Introduction and project overview
Introduction to the Maya's UV Texture Editor
Getting Familiar with the Planar Mapping
Exploring Cylindrical Mapping
Exploring Spherical and Automatic Mapping
Getting Started with Multiple Projections
Sewing UVs Together
Moving the UV Data from the polygon model to the original sub-d monster


wooden crate/shading 1

reality isn't perfect

first put logo on

luminance -- adjust level first and make higher contrast to remove parts of the logo

-- first layer of weathering

use repeating damage from grime pattern

-- use channel as selection to weather more

where did all the paint go?

take logo and smudge down...use same weathering on smudging
lower opacity, and change to overlay

next displace to make paint look like it's seeped into the grain

need a map with contrast on crevices of wood board, the rest is grey so it doesn't get pushed. It's a subtle effect, but makes a difference.

rest of wood is too clean...need to dirty it up some
-- add some spattering
--add soft layer of dirt
--edges is usally darker and dirt getting caught there
-- use adjusted, inverted channel from wood grain, mask out center and feather it, then use grime selection to remove some dirt and mult over

Then make bigger square, and apply same treatment to get narrow edge

extracting textures from images (label on crate)
convert to greyscale and adjust greyscale to be able to multiply

plank textures


3/03 Camera Properties Ð Rendering!

- Fundamental properties
bad camera work (or cinematography) can ruin an other wise good story or image
- camera
- camera aim
- camera aim and up

- the lens is the optical component of a real camera, it redirects (bends) the light onto the film to create an image. The nature of the bending of the light is dependent on the type of glass, the thickness, the curvature of the glass, etc.

-focal length - distance in mm from the center of the lense to the film plane
normal 30-55 (human eye, is about 50mm), telephoto >55, wideangle <28
-clipping planes
-show manipulator
-show interactive movement
-auto render clip plane (-1 0)
-z depth pass in render globals

- output settings (make camera renderable!) -- watch out for multiple renderable cameras in your scene
- Environment - background color
-image planes! what fun

- film back
o film gate, film back and film
o square v. non-sq pixels
o camera aperture Ð fstop in real camera Ð size of the opening of the camera, and thus the amount of light that can enter in to the lens
¥ The larger the fstop, the smaller the opening (less light goes in)
o Shutter speed is the time it takes for the shutter to completely open and close (measured in seconds)
¥ When the shutter is closed, the frame is moved to the next frame
¥ Narrow shutter angle restrict the motion blur
¥ Wider shutter angle will increase the motion blur
o Motion blur

- Frame rates
- Maya render globals
- Anti-aliasing and sampling
over sampling
adaptive over sampling
under sampling
- Depth of field
3 parameters
length of lens
distance at which camera is focused, diameter of aperture (f-stop)

Depth of field describes the photographic effect that occurs when a camera focuses at a particular distance. Objects that are nearly that distance from the camera appear to be in focus, while objects that are far from that distance are blurry. Most computer graphics cameras do not simulate out-of-focus objects, and this is equivalent to a pinhole camera.


Mental ray and rendering in passes

- plug-in load
- render globals
- what makes mental ray special
-3 renderers
-3 different kind of raytracing algorithm's
-global illumination
-final gather
-mental ray satellite for easy renderfarm setup

render passes

- why use them at all?
- hulk quicktime
- diffuse
- specular
- beauty
- ambient Occlusion
- shadow
- mattes
- rgb lights
- reflection w/bump
- smooth reflections
- spec
- grunge/scratches

putting passes into after effects/shake
-multiply ambient occlusion
-play with reflections, by changing opacity and screening reflection over
-use matte passes to isolate areas


general notes on 1st lighting assignment:

follow directions.
--label images
--locked camera
--camera for each render
--too many shadow casting lights
--low depth map resolution -- shadows look blocky
--texture are too large
--jpeg renders not so good....too much pixelation
--lights are really hot in some images.
--when raytracing, make sure you don't have super reflective surfaces...an apple is not as as reflective as a mirror
--textures 72 dpi...2k at the most -- can usually get away with 512k
--try to use a texture method that offeres lossless compression, such as sgi, targa, exr or tiff...be wary when compressing with tiff's LZW compression as mental ray is not able to use images with that compression.

-caustics -- need to enable photons in light--make sure you add photonic mental ray materials
-fg -- like GI except you only get one bounce (can enable secondary bounce, but not usual)
-hdri -- high dynamic range images...allow you to light very very realistic lighting conditions


3/31 Shading II

¥Build shading network for camouflage shirt.
¥fractal texture
¥layered texture
¥2d placement node
¥bump map
¥facing ratio

¥cd texture -- build a cd in class
displacement versus bump maps
stencil nodes?

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