Light

To have as realistic look I can create, I need to understand how light is going to act in my scene, and how I can use this to optimise my assets.
In this I shall be looking at light and it's physics, the way it reacts to certain materials (though some of this was covered in Rembrandt's works) and then how a computer can achieve this.
Unfortunately unlike my other posts this will be largely text, which I shall try and arrange, with little image use.

I started off reading a book called QED (Quantum Electrodynamics) written by Richard P. Feynman published in 1985. This book was meant to be teaching his wife about his life's work, theory of light and matter, but she died in 1982. So he instead decided to write it out as a book to help many other people. "The main purpose in these lectures is to describe as accurately as I can, the strand theory of light and matter - or more specifically, the interaction of light and electrons." (Feynman 1985 P4)

Firstly it is important to explain that other physics law had been found before light, sound being a motions of atoms in the air, heat also being described as motion however gravity is not motion and stands alone. And in 1873 a guy names James Clerk Maxwell proposed that light is an electromagnetic wave.
Around 1900 matter was better explained, to have a nucleus with electrons circling it. However in 1926 the theory "uncommon-sensy" explained new behaviours. This was called the Quantum theory (quantum here meaning an aspect of nature that goes against common sense). And thus Maxwell's theory had to be changed as magnetic light didn't fit with this new quantum theory. And in 1929 Quantum electrodynamics was established. And to this day physicists can't find anything wrong with it, as they love to find out new things.

The first thing about light is to understand that white light is a mixture of colours, as Newton found out but splitting them up using a glass prism. These different colours of light can be measured in a number called a frequency. As this frequency number gets higher the colours of light change from red to blue to violet to ultraviolet (which is unseen by the human eye). Any further up the scale and we go into X-rays, gamma rays etc. In the other direction you get red to infrared waves, television waves and radio waves.

What is light? (Unknown) Davici's World Available at <http://www.davincisworld.com/Light/WhatIsLight.htm> Accessed 28th October

(Light can also be split further using a process of polarisation as light travels up and down as well as side to side, and one way can be blocked. This is how 3D glasses are done these days.)

We know, after Newton wrongly calling the Corpuscles, that light is made from protons acting like particles. And we can measure and see this using a Photomultiplier.

(Feynman P15)

When a photon hits metal plate A an electron breaks loose from one of the atoms on the plate and goes straight to plate B s it's strongly attracted to it (being positively charged). Once it hits, the force breaks free more electrons off this plate and are attracted to plate C, and so even more are knocked loose. This is repeated 10 or 12 times until enough electrons (billions) hit the last plate L making a current which is amplified and sent to the speaker which makes a click noise.

Assume this:

• Light moves in straight lines
• It bends when it hits water
• It's reflected off surfaces like a mirror (being an equal angle it hits the mirror to when it leaves)

How Mirrors Work (2009) How Stuff Works Available at <http://static.howstuffworks.com/gif/mirror-light.jpg> Accessed 28th October 2012

For a piece of glass this is slightly different as it's a complicated material for it to move through. This can be seen using this experiment:

(Feynman P17)

A photomultiplier is placed at A to catch the reflected photons, another is also placed at B to measure how many photos get through the surface. Results found that for every 100 photons released at 90 degrees an average of 4 arrive at A and 96 arrive at B. Which show that it's only partially reflected while the rest goes through. This mystery of why certain light is reflected or not was a difficult problem for Newton.

One idea was that the glass was made up of holes and some went through, others didn't.

This idea was scrapped as Newton said "Because I can polish glass" (Feynman P18) and instead the idea that the particle has to be aimed just right to pass through was invited.

However all these ideas were unrefined at therefore we don't have a plausible idea of why certain particles move through a block and some are reflected. 

It was then later found that light reacts differently when travelling through different thicknesses of glass. And using the same experiment as above, they would place different thicknesses of glass in front of receiver B and see how many photons are being picked up at A.

Naturally as the thickness increased more and more photons were being reflected back to A. Once they hit 5 Millionth of an inch of glass reaches a maximum of 16% reflection, and increasing the thickness would make the reflection number gradually return back to 0%. But whats funny is that increasing it further would repeat the whole process again! And we get this effect:

(Feynman P22)

We need to then understand that different colours have different amounts of peaks and troughs (up and down). This one peak and trough is called a wavelength and different colours work in different rates, for example red and blue:

(Feynman P34)

This can be best described when looking at oil (or soap bubbles), as the oil film spreads out a moves around the surface of it's water it causes changing in viscosity (thickness of liquid) and so reflect different colours and parts of the wavelength and they hit it at different rates.

manf1234 (2007) Soap Bubble [YouTube video] Available at <http://www.youtube.com/watch?v=lRhUQTuEu3I&feature=related> Accessed 28th October 2012

The partial reflect of white light of 2 different surfaces is called iridescent and works on many other things like a hummingbird's and peacock's feathers.

Chapter 2

We are going to look at light being reflecting in mirrors more in-depth now. And it's important to understand how to calculate everything I'm explaining.

To start off with, we have the experiment ready, to see how much light is being reflected at G from S and read at P:

S is the light emitter

P is the photomultiplier

Q is a block to stop direct light

and the rest of the letters are the mirror split up to illustrate different places light could reflect from.

(Feynman P43)

Now all the reflective lines in the above image show the length the light will have to travel and each stage to be reflected back to P. This is something we want to narrow down to get a more accurate reading.

So we have the time it would take each light to get to P in the graph below this, and obviously it dips as it takes more, then less, then more time to be received at P.

From here we can establish time, and therefore get an accurate reading of arrows. *I didn't mention this before but these arrows can be used to predict light receiving by starting a stop watch, with a hand, when the proton is emitted and stopping it when received. This gives us an angle at which to draw the arrow, being the angle of the hand (The same direction towards the mirror opposite once reflected).

From here we can move onto the graph below this one and put together all these arrows to create this shape, and finally filling in the last arrow (the thicker line) shows us that arrows A-D and J-M wont have a large if any effect on the P receiver as it's not close to the direction of any of the other arrows.

This means that we can safely assume that no reflections from A-D and J-M on the mirror shall be picked up by P and not effecting our findings.

But also we can see that the ones that will be picked up are clearly at where the least time shall be taken to do so. And so we can say in the world that light moves where it would take the least amount of time doing so. And therefore the other parts of the mirror cancel each other out (proven by looking at these parts and having the arrows left forming a complete circle.) Leaving G the main and most important part of reflection, being an equal angle from the light going towards and being reflected back against the mirror.

Some mirrors have been scratched away at certain points to reflect only certain parts of light (reflect certain angles of those arrows) for example a DVD shines those colours when you rotate it, this is because this is happening:

(Feynman P48)

Now we shall look at light going through air and water. And now we place the photomultiplier underwater.

(Feynman P50)

Again the same principle showing that light will go the least time from S to D through water. From this we can establish, and must know, that light travels slowing in water (which I shall look at why later) and this explains other forms of light and water. It is then interesting to look at why mirages happen when there in no water on the floor (when driving for example). Light goes slower through cooler air than it does warmer air and for someone to see a mirage they must be in the cooler air looking down at the hot air nearer the ground. And this can all be understood by finding the path of least time light has to travel.

(Feynman P52)

So as light goes in a straight line, we can accurately angle it to react how we like, if we know the physics. The previous graphs showing light through water showing that light arrives at the photomultiplier at different times because they enter differently and therefore taken different time to arrive. However if we do this using a lens type (glass) we can make light arrive equally at the one point P.

(Feynman P58)

This is similar to how the eye works, focusing light so we can see clear images and not a jumble of different ranges of light arriving at different times.

To look at transmission of light we can set this experiment up and look at the way light has turned (it's angle) and shrunk (in intensity). This is to prove how more

(Feynman P70)

For this I shall explain how light is acting. 

1. Photon goes through the air, turning but not shrinking

2. Photon passes through glass, not turning but shrinking to 0.98

3. Photo goes through the glass, turning and not shrinking

4. Reflection off the back, no turning but shrinking that 0.2 of 0.98 = 0.192

5. Photon back through the glass, turning not shrinking

6. Reflects off front surface, not turning but shrinking to 0.0392

7. Back through glass again, turning and no shrinking

8. Through back surface glass, not turning but again shrinking to 0.0384

9. It goes to the detector, turning but not shrinking

The turns made in 3 and 5 are exactly equal to 5 and 7 which helps us state that "when the probability of reflection in 0, the probability of transmission is 100%" (Feynman P71) And therefore in nature 100% of the photons are accounted for, as I know and should explain to you that energy (which light is a form of) can not be destroyed or created only transformed. 

Feynman, R. (1985) QED Penguin Books.

Light reaction

Light reacts in 3 main ways when connecting with a surface:

• Absorption
• Reflection
• Refraction

Absorption works as light hits the surface it is absorbed, this is because light is converted into another form of energy, usually heat which is why it can be absorbed by the material. This is caused by the vibrations of the atoms of the material's surface and effects the objects darkness or opacity.

Harris, William (Unknown) Pigments and Absorption How Stuff Works Available at <http://science.howstuffworks.com/light12.htm> Accessed 29th October 2012

This is why we see colours. The certain frequency of the waves that have been absorbed have been taken away from the white light and those left bounce back, which is that colour the eye sees. For example the green of plant leaves contain chlorophyll which absorb the reds and blues, so reflecting green back to the eye, and therefore being green.

Reflection works as I have explained above, but it's important to know that is is happening on everything and everywhere. A direct reflection like on a mirror causes an image to be bounced back, however reflection on a rock would diffuse the light scattering it into different directions so no visible image can be seen.

Vollmer, Jan (2008) 3ds MAX +VRay Tutorial :: Time in Running CGIndia Available at <http://cg-india.com/tutorials/3dsmax_makkingof02.html> Accessed 29th October 2012

Refraction happens when light is being "bent" into a new direction when it hits a new density surface for example most commonly glass and water. When hitting its surface, the more acute the angle, the more of a chance it passes through, being refracted, and therefore the more acute the angle is in the new material.
At a perfect refraction of glass we can split light up into all the different frequencies of colour. this is because when the white light is angled perfectly against the prism each frequency of the light is refracted at a different angle causing it to split.

Light (Unknown) Wordpress Available at <http://feigel.files.wordpress.com/2011/02/light.jpg> Accessed 29th October 2012

This also helps us explain why sometimes you can see through surface of water, and sometimes not. (leaving out the the cleanness of the water) If the light's angle when hitting the water is too sharp, then most of it would get reflected back to the eye, so you'd only see the surface. If the angle was obtruse it would pass through and reflect back to the eye off anything underneath the surface.

Light and Shadow

When talking about light, it is obvious that it comes hand in hand with shadows. Therefore when creating my scene it is important to consider the concentration of my light, and the dynamic occlusion.
It is then easy to assume that when light isn't very concentrated, filling a room equally the objects will seem softer, with colours less intense. In comparison if the light is harsher, for example a spot light then the colours will be more intense with the effect of Chiaroscuro. (The light against dark shadows, much like Rembrandt's work.)
Dynamic Occlusion is slightly different as it's about the shadow. The idea being that the further away the shadow gets from its original, the subject, starting point the less concentrated it becomes as other light around it effects it. This can be easily described when shading, starting with the dark under shadow, and fading it out to light areas.

Materials

As I will be working with some materials in my scene I wanted to look at some that may be relevant, and illustrate them here.

Teddy/Toy fur reflecting light

fangzhengcn (2009) Teddy Bear Lapm/light - NEW!! PRlog Available at <http://www.prlog.org/10328851-teddy-bear-lamplight-new.html> Accessed 29th October 2012

Wood and light partial absorption when wood is thin.

Robin, Julian (2010) Solid Wood Light Yaean Design Available at < http://www.yaean.com/en/blog/2010/07/06/solid-wood-light/> Accessed 29th October 2012

Water being reflected of it's surface and below it (3D)

White, Elliot (2008) Roof Pool, Blog Available at < http://www.yaean.com/en/blog/2010/07/06/solid-wood-light/> Accessed 29th October 2012

Plastic absorbing light

Eugene, Oregon (2007) New Plastic Light Revealed PRWeb Available at <http://www.prweb.com/releases/2007/06/prweb534851.htm> Accessed 29th October 2012

Mirrors image unless reflected exactly distorts and glass reflect partial so slight obscures view

(Own image)

Massey, Anne (1990) Interior design of the 20th century p.204

Clothing in light causes creases, and folds to show up.

(Own image)

This study of light are just a few things I need to look into to create my scene, but now I know the physics of real light I can look at light used in the computer and how that replicated.

Digital Light

By studying [digital] Light & Rendering by Jeremy Birn I have learned a lot about how I can use lights in my scene to create a realistic look. This book is for all the main 3D softwares and therefore some of the lights may have a different name when I come across it etc.
A well light scene is important to show off tones and textures, without it an object you've put so much time in could be wasted if it's not set up properly.
This first thing this book mentions is about settings on a monitor to see.

To start with I should turn off all my light in the scene, this is so I have complete control over my lightings. In real life artists will do this to see what natural lighting will occur. Though this isn't the case in a computer scene, it's still good for control.

I should then look into what ambient light does to the scene, this light is the natural light that bounces off everything filling a room. However it doesn't look amazing on a computer sometimes and must be checked.

(Birn p.12)

Now to add light sources I must understand what a couple of them mean.

• Point (omnidirectional) Lights - Is a light, much like a light bulb or a star, that emits light uniformly in all directions away from it's source. However real light doesn't work like this as, for example a bulb, has a metal socket that stops light going in that direction. You can do this in 3D by either applying a texture map to the light or placing the light in a 3D objects that blocks parts of the emitted light. (Lampshade)
• Spotlights - are popular to control the light aimed at a specific target. These lights are limited in illumination within the specific beam, unlike point light. The lights can be rotated to be aimed anywhere, set to follow a target, or aimed as if they were attached to an object. (Useful for car headlights) This can be adjusted to harsh and soft light, positive or negative light, and can be used to slightly lighten and darken areas, such as windows and room corners.
• Directional Light - makes the light source seem further away than other lights, as the shadows casted become parallel to one another. It works by setting a single vector and hitting each objects at the same angle no matter where they are placed in the scene. This light can be used along side other lights, as a main fill room light source, and is said to look better than ambiance. (above image right)
• Area Lights - Is a more realistic type of lighting as all rays are not emitted from the same point. If the point is larger the light appears softer, with softer shadows and a 'wrap around' effect on objects. However because this light is high quality it adds time to the rendering, and isn't ideal for quickly rendered animations, but good for still life high-quality images.
• Spherical Area Lights - Being similar to Area Lights, though specifically spherical, these ones can be used when the object is closer, instead of the point light. It means the light being let off is more diffused and softer.
• Flat Area Lights - These take shape like a ceiling light and have a still soft diffuse emitted light source. And changing the rotation does have an effect on the scene. As well as this, the flat are light can be used to simulate the reflection from brightly lit walls and ceilings, which provides a soft and realistic light for portraits and still life renderings.
• Linear Lights - Are similarly laid out to fluorescent and laser lights. This can only be adjusted one way, long ways. This light can also be aimed to effect the subject, the linear sides are softer but the end lights are harsher, more focused. This light can be used to general soft light as it doesn't add to the rendering time as it's only emitting from one axis rather than two or three.
• Models Serving as Light - This is basically what it says it is, using 3D models you've created as a light source.

 FOOTBALL PLAYER SHADOWS AND LIGHTS

Birn, Jeremy (2000) [digital] Light & Rendering, New Riders

COLOUR

Light is related to colour, and using the notes I took in Marie-Claire's lecture on colour, I will talk a little about it.

The perception of colour is a sensory experience. And white colour is a mixture of all colours, relating to how light works, and black has no colour. Which is why we can't see much in the dark, and why all the colour becomes desaturated.

• Hue is described as a colour family of pure colours, which can be played around with in photoshop and has no link to blackness or whiteness of colour.
• Saturation is the strength of a colour, which can be changed to look more along a grey scale rather than intense colour.
• Lightness is the addition of black and white, being mixed up with saturation, however the subtle difference being that a colour become lighter or darker, changing colour and not loosing it's colour.

In colour pigments, when mixing paint, yellow, blue and red mixed become black, however in light terms yellow, blue and red becomes white. Which is also the case on a computer, being the RGB scale. Though when printing these colours change to become Yellow, Magenta, Cyan, which must be taken into consideration when printing out pieces of work.

We see a certain amount of colours where as some animals, like butterflies, bees and birds can see ultraviolet light, and also a bull actually see's in black and white, which undermines the whole red cape Spanish games.

First seen in rainbows, people painted them as they looked upon this phenomenon. Light was looked into by many theorists, with different ideas on how it worked:

• Pythagoras thought light came as beams coming from the persons eye it's self. and would rest upon the object they were looking at.
• Aristotle talked about rainbows being reflections of raindrops, which he was right about.
• Aron Forsius came up with the first drawn colour-system.
• Athanasius Kircher showed linear diagrams of the RGB colour-system and often wondered why the sky was blue.
• Isaac Newton discovered the splitting of light forming the mixture of colours, the rainbow. And split his light understand them.
• Ignaz Schiffermuller's colour-systems derived more colours like sea-green, olive-green.

Colour and light used in paintings can be found in 1836 by John Constable seeing a rainbow.

Constable, John (1836) Art Work of the Month - May 2002 [internet] Available at <http://www.liverpoolmuseums.org.uk/nof/aotm/displaypicture.asp?venue=&id=120> Accessed 18th November 2012

Robert S Duncanson 1859, another rainbow

Duncanson, Robert (1859) Midterm 1, Study Blue [Blog] Available at <http://www.studyblue.com/notes/note/n/midterm-1/deck/168927> Accessed 18th November 2012

In early days paint would have to made when needed, as it wouldn't keep well at all. Colour men, were people that worked for the artist, if they had the money, and would create these colours by mixing the correct mixtures, being very expensive they had to do it correctly. 

This means the paints we use now, from the shops in a tube, aren't the correct exact colour pigments, though theres one shop in London that do create exact colour pigments like before: http://www.cornelissen.com/

Different colours can be seen on different computer screens, cos not two screens are exactly the same. This is why when TV was adjusting itself there would come up before a program, a test card with the image of a girl and her clown toy. This was so that anyone wanting to watch the programme could switch their set to match the test sheet as some films,

Test Card (2012) KSL, Available at <http://www.stevelarkins.freeuk.com/tvtools.htm> Accessed 18th November 2012

 and shows are set to a certain colour, like Amelie is very red and green showing it's in her own world.

Amelie (2012) MBTI IN FICTION [blog] Available at <http://mbti-in-fiction.tumblr.com/post/32526307368/amelie-poulain> Accessed 18th November 2012

Children also see colours differently, being brighter and not as developed, which is why this film could have also been shot in this colour palette. 

The wizard of oz, was the first Technicolour film with the yellow brick road and the red shoes.

Understanding colour can help create better work as the use of colour is important for realism.