Space bodies’ components and light spectroscopy
www.plutorules.com/page-111-space-rocks.html
This help’s us understand the composition of components in/on solar system bodies.
Dips in the observed light spectrum, also known as, lines of absorption occur as gasses absorb energy from light at specific points along the light spectrum.
These dips or darkened zones (lines of absorption) leave a finger print which identify elements and compounds.
In this image the dark absorption bands appear as lines of emission which occur as the result of emitted not reflected (absorbed) light.
Lines of absorption
What light is best to illuminate gems for resale
www.palagems.com/gem-lighting2
Artificial light sources, not unlike the diverse phases of natural light, vary considerably in their properties. As a result, some lamps render an object’s color better than others do.
The most important criterion for assessing the color-rendering ability of any lamp is its spectral power distribution curve.
Natural daylight varies too much in strength and spectral composition to be taken seriously as a lighting standard for grading and dealing colored stones. For anything to be a standard, it must be constant in its properties, which natural light is not.
For dealers in particular to make the transition from natural light to an artificial light source, that source must offer:
1- A degree of illuminance at least as strong as the common phases of natural daylight.
2- Spectral properties identical or comparable to a phase of natural daylight.
A source combining these two things makes gems appear much the same as when viewed under a given phase of natural light. From the viewpoint of many dealers, this corresponds to a naturalappearance.
The 6000° Kelvin xenon short-arc lamp appears closest to meeting the criteria for a standard light source. Besides the strong illuminance this lamp affords, its spectrum is very similar to CIE standard illuminants of similar color temperature.
What Is The Resolution and view coverage Of The human Eye. And what distance is TV at best?
https://www.discovery.com/science/mexapixels-in-human-eye
About 576 megapixels for the entire field of view.
Consider a view in front of you that is 90 degrees by 90 degrees, like looking through an open window at a scene. The number of pixels would be:
90 degrees * 60 arc-minutes/degree * 1/0.3 * 90 * 60 * 1/0.3 = 324,000,000 pixels (324 megapixels).
At any one moment, you actually do not perceive that many pixels, but your eye moves around the scene to see all the detail you want. But the human eye really sees a larger field of view, close to 180 degrees. Let’s be conservative and use 120 degrees for the field of view. Then we would see:
120 * 120 * 60 * 60 / (0.3 * 0.3) = 576 megapixels.
Or.
7 megapixels for the 2 degree focus arc… + 1 megapixel for the rest.
https://clarkvision.com/articles/eye-resolution.html
How many megapixels do you really need?
https://www.tomsguide.com/us/how-many-megapixels-you-need,review-1974.html
Single vs Dual Processor Servers – CPUs, cores and threads
phoenixnap.com/kb/single-vs-dual-processors-server
The backbone of any server is the number of CPUs that will power it, as well as the actual model and the type of the CPU. From that point, you add the needed amount of RAM, storage and other options that your use case requires.
A CPU (Central Processing Unit) is a piece of hardware responsible for executing tasks from other parts of a computer.
A Core is a physical part of a CPU. Cores act like processors within a single CPU chip. The more cores a CPU has, the more tasks it can perform simultaneously. Virtually all modern CPUs contain multiple cores now. This enables the execution of multiple tasks at the same time.
Threads are like paths your computer can take to process information.
If a CPU has six cores with two threads per core, that means there are twelve paths for information to be processed. The main difference between threads and physical cores is that two threads cannot operate in parallel. While two physical cores can simultaneously perform two tasks, one core alternates between the threads. This happens fast so that it appears that true multitasking takes place. Threads basically help the cores process information in a more efficient manner. That being said, CPU threads bring actual, visible performance in very specific tasks, so a hyper-threaded CPU might not always help you achieve better results.
Single processor servers run on a motherboard with one socket for a CPU. This means that the highest core count CPU available on the market determines the maximum core count per server. RAM capacity constraints with single CPU configurations remain one of their biggest drawbacks.
The most apparent distinction between single and dual-processor servers is that the motherboard has two CPU sockets instead of one. This is followed by additional benefits such as the massive amount of PCI lanes, two separate sets of cache memory and two sets of RAM slots. If the specific motherboard has 24 memory slots, 12 slots belong to the first CPU and the other 12 to the other CPU. In cases where only one CPU slot occupied, the CPU cannot use the other set of RAM sticks. This rarely happens since dual processor servers always have both slots occupied. Dual processor servers and multiprocessor systems, in general, are the best options for space-restricted environments.
While dual CPU setups pack enormous core counts and outshine single processor servers by a large margin, some tests have shown only a marginal performance increase over single CPU configurations with similar core count and clock speeds per chip. This refers to the circumstances where two CPUs worked on the same data at the same time.
On the other hand, we see immense performance boosts in dual processor servers when the workload is optimized for setups like these. This is especially true when CPUs carry out intensive multi-threaded tasks.
www.techsiting.com/cores-vs-threads/
Material X – an open standard for transfer of rich material and look-development content
MaterialX is an open standard for transfer of rich material and look-development content between applications and renderers.
Originated at Lucasfilm in 2012, MaterialX has been used by Industrial Light & Magic in feature films such as Star Wars: The Force Awakens and Rogue One: A Star Wars Story, and by ILMxLAB in real-time experiences such as Trials On Tatooine.
MaterialX addresses the need for a common, open standard to represent the data values and relationships required to transfer the complete look of a computer graphics model from one application or rendering platform to another, including shading networks, patterns and texturing, complex nested materials and geometric assignments.
To further encourage interchangeable CG look setups, MaterialX also defines a complete set of data creation and processing nodes with a precise mechanism for functional extensibility.
Open Source Nvidia Omniverse
blogs.nvidia.com/blog/2019/03/18/omniverse-collaboration-platform/
developer.nvidia.com/nvidia-omniverse
An open, Interactive 3D Design Collaboration Platform for Multi-Tool Workflows to simplify studio workflows for real-time graphics.
It supports Pixar’s Universal Scene Description technology for exchanging information about modeling, shading, animation, lighting, visual effects and rendering across multiple applications.
It also supports NVIDIA’s Material Definition Language, which allows artists to exchange information about surface materials across multiple tools.
With Omniverse, artists can see live updates made by other artists working in different applications. They can also see changes reflected in multiple tools at the same time.
For example an artist using Maya with a portal to Omniverse can collaborate with another artist using UE4 and both will see live updates of each others’ changes in their application.
Double Negative pulls plans of listing on Stock Exchange
DNEG said last month it was looking to raise £150m from a float on the LSE’s Main Market. This valued the firm at more than £600m.
But yesterday it said it has decided to postpone the listing due to ‘ongoing market uncertainty’.
The London-based group added that it had received ‘a strong level of interest from investors’ and still intends to go public once market conditions improve.
Magic Leap looking for 9th round of investments
Having burned through $2.6bn – that’s billion – on its way to producing an AR headset that has so many limitations it seemingly has zero chance of becoming a consumer device, the upstart has announced it is now part way through series E funding.
That’s just a Silicon Valley way of saying it’s on a fifth formal round of begging to banks and venture capitalists to help it keep going before the biz finally starts making money. In reality, it is the manufacturer’s eighth funding round, with the most recent being a cash influx of $280m in April this year. That money appears to be running out, or just simply not enough, just six months later.
www.theregister.co.uk/2019/11/14/magic_leap_imoney/
MagicLeap loses cfo Scott Henry and effects wizard John Gaeta following news of funding woes
MDL – NVidia Material Definition Language
www.nvidia.com/en-us/design-visualization/technologies/material-definition-language/
THE NVIDIA MATERIAL DEFINITION LANGUAGE (MDL) gives you the freedom to share physically based materials and lights between supporting applications.
For example, create an MDL material in an application like Allegorithmic Substance Designer, save it to your library, then use it in NVIDIA® Iray® or Chaos Group’s V-Ray, or any other supporting application.
Unlike a shading language that produces programs for a particular renderer, MDL materials define the behavior of light at a high level. Different renderers and tools interpret the light behavior and create the best possible image.
Photography basics: How Exposure Stops (Aperture, Shutter Speed, and ISO) Affect Your Photos – cheat cards
Also see:
http://www.pixelsham.com/2018/11/22/exposure-value-measurements/
http://www.pixelsham.com/2016/03/03/f-stop-vs-t-stop/
An exposure stop is a unit measurement of Exposure as such it provides a universal linear scale to measure the increase and decrease in light, exposed to the image sensor, due to changes in shutter speed, iso and f-stop.
+-1 stop is a doubling or halving of the amount of light let in when taking a photo
1 EV (exposure value) is just another way to say one stop of exposure change.
https://www.photographymad.com/pages/view/what-is-a-stop-of-exposure-in-photography
Same applies to shutter speed, iso and aperture.
Doubling or halving your shutter speed produces an increase or decrease of 1 stop of exposure.
Doubling or halving your iso speed produces an increase or decrease of 1 stop of exposure.
Because of the way f-stop numbers are calculated (ratio of focal length/lens diameter, where focal length is the distance between the lens and the sensor), an f-stop doesn’t relate to a doubling or halving of the value, but to the doubling/halving of the area coverage of a lens in relation to its focal length. And as such, to a multiplying or dividing by 1.41 (the square root of 2). For example, going from f/2.8 to f/4 is a decrease of 1 stop because 4 = 2.8 * 1.41. Changing from f/16 to f/11 is an increase of 1 stop because 11 = 16 / 1.41.
A wider aperture means that light proceeding from the foreground, subject, and background is entering at more oblique angles than the light entering less obliquely.
Consider that absolutely everything is bathed in light, therefore light bouncing off of anything is effectively omnidirectional. Your camera happens to be picking up a tiny portion of the light that’s bouncing off into infinity.
Now consider that the wider your iris/aperture, the more of that omnidirectional light you’re picking up:
https://frankwhitephotography.com/index.php?id=28:what-is-a-stop-in-photography
The great thing about stops is that they give us a way to directly compare shutter speed, aperture diameter, and ISO speed. This means that we can easily swap these three components about while keeping the overall exposure the same.
http://lifehacker.com/how-aperture-shutter-speed-and-iso-affect-pictures-sh-1699204484
https://www.techradar.com/how-to/the-exposure-triangle
https://www.videoschoolonline.com/what-is-an-exposure-stop/
Note. All three of these measurements (aperture, shutter, iso) have full stops, half stops and third stops, but if you look at the numbers they aren’t always consistent. For example, a one third stop between ISO100 and ISO 200 would be ISO133, yet most cameras are marked at ISO125.
Third-stops are especially important as they’re the increment that most cameras use for their settings. These are just imaginary divisions in each stop.
From a practical standpoint manufacturers only standardize the full stops, meaning that while they try and stay somewhat consistent there is some rounding up going on between the smaller numbers.
Note that ND Filters directly modify the exposure triangle.
Joe Letteri on Production, VFX and storytelling
nerdist.com/article/joe-letteri-avatar-alita-battle-angel-james-cameron-martin-scorsese/
[Any] story [has to be] complete in itself. If there are gaps that you’re hoping will be filled in with visual effects, you’re likely to be disappointed. We can add ideas, we can help in whatever way that we can, but you want to make sure that when you read it, it reads well.
[Our responsibility as VFX artist] I think first and foremost [is] to engage the audience. Everything that we do has to be part of the audience wanting to sit there and watch that movie and see what happens next. And it’s a combination of things. It’s the drama of the characters. It’s maybe what you can do to a scene to make it compelling to look at, the realism that you might need to get people drawn into that moment. It could be any number of things, but it’s really about just making sure that you’re always in mind of how the audience is experiencing what they’re seeing.
What’s the Difference Between Ray Casting, Ray Tracing, Path Tracing and Rasterization? Physical light tracing…
RASTERIZATION
Rasterisation (or rasterization) is the task of taking the information described in a vector graphics format OR the vertices of triangles making 3D shapes and converting them into a raster image (a series of pixels, dots or lines, which, when displayed together, create the image which was represented via shapes), or in other words “rasterizing” vectors or 3D models onto a 2D plane for display on a computer screen.
For each triangle of a 3D shape, you project the corners of the triangle on the virtual screen with some math (projective geometry). Then you have the position of the 3 corners of the triangle on the pixel screen. Those 3 points have texture coordinates, so you know where in the texture are the 3 corners. The cost is proportional to the number of triangles, and is only a little bit affected by the screen resolution.
In computer graphics, a raster graphics or bitmap image is a dot matrix data structure that represents a generally rectangular grid of pixels (points of color), viewable via a monitor, paper, or other display medium.
With rasterization, objects on the screen are created from a mesh of virtual triangles, or polygons, that create 3D models of objects. A lot of information is associated with each vertex, including its position in space, as well as information about color, texture and its “normal,” which is used to determine the way the surface of an object is facing.
Computers then convert the triangles of the 3D models into pixels, or dots, on a 2D screen. Each pixel can be assigned an initial color value from the data stored in the triangle vertices.
Further pixel processing or “shading,” including changing pixel color based on how lights in the scene hit the pixel, and applying one or more textures to the pixel, combine to generate the final color applied to a pixel.
The main advantage of rasterization is its speed. However, rasterization is simply the process of computing the mapping from scene geometry to pixels and does not prescribe a particular way to compute the color of those pixels. So it cannot take shading, especially the physical light, into account and it cannot promise to get a photorealistic output. That’s a big limitation of rasterization.
There are also multiple problems:
-
If you have two triangles one is behind the other, you will draw twice all the pixels. you only keep the pixel from the triangle that is closer to you (Z-buffer), but you still do the work twice.
-
The borders of your triangles are jagged as it is hard to know if a pixel is in the triangle or out. You can do some smoothing on those, that is anti-aliasing.
-
You have to handle every triangles (including the ones behind you) and then see that they do not touch the screen at all. (we have techniques to mitigate this where we only look at triangles that are in the field of view)
-
Transparency is hard to handle (you can’t just do an average of the color of overlapping transparent triangles, you have to do it in the right order)
RAY CASTING
It is almost the exact reverse of rasterization: you start from the virtual screen instead of the vector or 3D shapes, and you project a ray, starting from each pixel of the screen, until it intersect with a triangle.
The cost is directly correlated to the number of pixels in the screen and you need a really cheap way of finding the first triangle that intersect a ray. In the end, it is more expensive than rasterization but it will, by design, ignore the triangles that are out of the field of view.
You can use it to continue after the first triangle it hit, to take a little bit of the color of the next one, etc… This is useful to handle the border of the triangle cleanly (less jagged) and to handle transparency correctly.
RAYTRACING
Same idea as ray casting except once you hit a triangle you reflect on it and go into a different direction. The number of reflection you allow is the “depth” of your ray tracing. The color of the pixel can be calculated, based off the light source and all the polygons it had to reflect off of to get to that screen pixel.
The easiest way to think of ray tracing is to look around you, right now. The objects you’re seeing are illuminated by beams of light. Now turn that around and follow the path of those beams backwards from your eye to the objects that light interacts with. That’s ray tracing.
Ray tracing is eye-oriented process that needs walking through each pixel looking for what object should be shown there, which is also can be described as a technique that follows a beam of light (in pixels) from a set point and simulates how it reacts when it encounters objects.
Compared with rasterization, ray tracing is hard to be implemented in real time, since even one ray can be traced and processed without much trouble, but after one ray bounces off an object, it can turn into 10 rays, and those 10 can turn into 100, 1000…The increase is exponential, and the the calculation for all these rays will be time consuming.
Historically, computer hardware hasn’t been fast enough to use these techniques in real time, such as in video games. Moviemakers can take as long as they like to render a single frame, so they do it offline in render farms. Video games have only a fraction of a second. As a result, most real-time graphics rely on the another technique called rasterization.
PATH TRACING
Path tracing can be used to solve more complex lighting situations.
Path tracing is a type of ray tracing. When using path tracing for rendering, the rays only produce a single ray per bounce. The rays do not follow a defined line per bounce (to a light, for example), but rather shoot off in a random direction. The path tracing algorithm then takes a random sampling of all of the rays to create the final image. This results in sampling a variety of different types of lighting.
When a ray hits a surface it doesn’t trace a path to every light source, instead it bounces the ray off the surface and keeps bouncing it until it hits a light source or exhausts some bounce limit.
It then calculates the amount of light transferred all the way to the pixel, including any color information gathered from surfaces along the way.
It then averages out the values calculated from all the paths that were traced into the scene to get the final pixel color value.
It requires a ton of computing power and if you don’t send out enough rays per pixel or don’t trace the paths far enough into the scene then you end up with a very spotty image as many pixels fail to find any light sources from their rays. So when you increase the the samples per pixel, you can see the image quality becomes better and better.
Ray tracing tends to be more efficient than path tracing. Basically, the render time of a ray tracer depends on the number of polygons in the scene. The more polygons you have, the longer it will take.
Meanwhile, the rendering time of a path tracer can be indifferent to the number of polygons, but it is related to light situation: If you add a light, transparency, translucence, or other shader effects, the path tracer will slow down considerably.
blogs.nvidia.com/blog/2018/03/19/whats-difference-between-ray-tracing-rasterization/
https://en.wikipedia.org/wiki/Rasterisation
https://www.dusterwald.com/2016/07/path-tracing-vs-ray-tracing/
https://www.quora.com/Whats-the-difference-between-ray-tracing-and-path-tracing
Photography basics: Color Temperature and White Balance
Color Temperature of a light source describes the spectrum of light which is radiated from a theoretical “blackbody” (an ideal physical body that absorbs all radiation and incident light – neither reflecting it nor allowing it to pass through) with a given surface temperature.
https://en.wikipedia.org/wiki/Color_temperature
Or. Most simply it is a method of describing the color characteristics of light through a numerical value that corresponds to the color emitted by a light source, measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000.
More accurately. The color temperature of a light source is the temperature of an ideal backbody that radiates light of comparable hue to that of the light source.
As such, the color temperature of a light source is a numerical measurement of its color appearance. It is based on the principle that any object will emit light if it is heated to a high enough temperature, and that the color of that light will shift in a predictable manner as the temperature is increased. The system is based on the color changes of a theoretical “blackbody radiator” as it is heated from a cold black to a white hot state.
So, why do we measure the hue of the light as a “temperature”? This was started in the late 1800s, when the British physicist William Kelvin heated a block of carbon. It glowed in the heat, producing a range of different colors at different temperatures. The black cube first produced a dim red light, increasing to a brighter yellow as the temperature went up, and eventually produced a bright blue-white glow at the highest temperatures. In his honor, Color Temperatures are measured in degrees Kelvin, which are a variation on Centigrade degrees. Instead of starting at the temperature water freezes, the Kelvin scale starts at “absolute zero,” which is -273 Centigrade.
More about black bodies here: http://www.pixelsham.com/2013/03/14/black-body-color
The Sun closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is about 5780 K. The color temperature of sunlight above the atmosphere is about 5900 K. Time of the day and atmospheric conditions bias the purity of the light that reaches us from the sun.
Some think that the Sun’s output in visible light peaks in the yellow. However, the Sun’s visible output peaks in the green:
http://solar-center.stanford.edu/SID/activities/GreenSun.html
Independently, we refer to the sun as a pure white light source. And we use its spectrum as a reference for other light sources.
Because the sun’s spectrum can change depending on so many factors (including pollution), a standard called D65 was defined (by the International Commission on Illumination) to represent what is considered as the average spectrum of the sun in average conditions.
This in reality tends to bias towards an overcast day of 6500K. And while it is implemented at different temperatures by different manufacturers, it is still considered a more common standard.
https://en.wikipedia.org/wiki/Illuminant_D65
https://www.scratchapixel.com/lessons/digital-imaging/colors
In this context, the White Point of a light defines the neutral color of its given color space.
https://chrisbrejon.com/cg-cinematography/chapter-1-color-management/#Colorspace
D65 corresponds to what the spectrum of the sun would typically look like on a midday sun somewhere in Western/Northern Europe (figure 9). This D65 which is also called the daylight illuminant is not a spectrum which we can exactly reproduce with a light source but rather a reference against which we can compare the spectrum of existing lights.
Another rough analogue of blackbody radiation in our day to day experience might be in heating a metal or stone: these are said to become “red hot” when they attain one temperature, and then “white hot” for even higher temperatures.
Similarly, black bodies at different temperatures also have varying color temperatures of “white light.” Despite its name, light which may appear white does not necessarily contain an even distribution of colors across the visible spectrum.
The Kelvin Color Temperature scale imagines a black body object— (such as a lamp filament) being heated. At some point the object will get hot enough to begin to glow. As it gets hotter its glowing color will shift, moving from deep reds, such as a low burning fire would give, to oranges & yellows, all the way up to white hot.
Color temperatures over 5,000K are called cool colors (bluish white), while lower color temperatures (2,700–3,000 K) are called warm colors (yellowish white through red)
Our eyes are very good at judging what is white under different light sources, but digital cameras often have great difficulty with auto white balance (AWB) — and can create unsightly blue, orange, or even green color casts. Understanding digital white balance can help you avoid these color casts, thereby improving your photos under a wider range of lighting conditions.
White balance (WB) is the process of removing these color casts from captured media, so that objects which appear white in perception (or expected) are rendered white in your medium.
This color cast is due to the way light itself is formed and spread.
What a white balancing procedure does is it identifies what is white in your footage. It doesn’t know what white is until you tell it what it is.
You can often do this with AWB (Automatic White Balance), but the results are not always desirable. That is why you may choose to manually change your white balance.
When you white balance you are telling your camera to treat any object with similar chrominance and luminance as white.
Different type of light sources generate different color casts.
As such, camera white balance has to take into account this “color temperature” of a light source, which mostly refers to the relative warmth or coolness of white light.
Matching the temperature value of an indoor/outdoor cast makes for a white balance.
The two color temperatures you’ll hear most often discussed are outdoor lighting which is often ball parked at 5600K and indoor (tungsten) lighting which is generally ball parked at 3200K. These are the two numbers you’ll hear over and over again. Higher color temperatures (over 5000K) are considered “cool” (i.e. Blue’ish). Lower color temperatures (under 5000K) are considered “warm” (i.e. orange’ish).
Therefore if you are shooting indoors under tungsten lighting at 3200K you will set your white balance for indoor shooting at this color temperature. In this case, your camera will correct your camera’s settings to ensure that white appears white. Your camera will either have an indoor 3200K auto option (even the most basic camera’s have this option) or you can choose to set it manually.
Things get complicated if you’re filming indoors during the day under tungsten lighting while the outdoor light is coming through a window. Now what we have is a mixing of color temperatures. What you need to understand in this situation is that there is no perfect white balance setting in a mixed color temperature setting. You will need to make a compromise on one end of the spectrum or the other. If you set your white balance to tungsten 3200K the daylight colors will appear very blue. If you set your white balance to optimize for daylight 5600K then your tungsten lighting will appear very orange.
Where to use which light:
For lighting building interiors, it is often important to take into account the color temperature of illumination. A warmer (i.e., a lower color temperature) light is often used in public areas to promote relaxation, while a cooler (higher color temperature) light is used to enhance concentration, for example in schools and offices.
REFERENCES
How to Convert Temperature (K) to RGB: Algorithm and Sample Code
https://tannerhelland.com/2012/09/18/convert-temperature-rgb-algorithm-code.html
http://www.vendian.org/mncharity/dir3/blackbody/UnstableURLs/bbr_color.html
http://riverfarenh.com/light-bulb-color-chart/
https://www.lightsfilmschool.com/blog/filmmaking-white-balance-and-color-temperature
https://astro-canada.ca/le_spectre_electromagnetique-the_electromagnetic_spectrum-eng
http://www.3drender.com/glossary/colortemp.htm
http://pernime.info/light-kelvin-scale/
http://lowel.tiffen.com/edu/color_temperature_and_rendering_demystified.html
https://en.wikipedia.org/wiki/Color_temperature
How to Convert Temperature (K) to RGB:
http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_for_cinema_4d_ci_Lights_html
