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Human Visual System & 3D Visualization Systems

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Human Visual System & 3D Visualization Systems Human Visual System & 3D Visualization Systems Felix G. Hamza-Lup, Ph.D Associate Professor, Director NEWS Lab Computer Science and Information Technology Armstrong Atlantic State University Savannah, Georgia, USA Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 1 Outline • Human Visual System • Components • Limitations/Deficiencies • Optical Illusions • Light and Colors • Light Properties • Artificial Light Sources • Color Models • 3D Visualization Systems Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 2 The Human • Information i/o … • visual, auditory, haptic, movement • Information stored in memory • sensory, short-term, long-term • Information processed and applied • reasoning, problem solving, skill, error • Emotion influences human capabilities • Each person is different Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 3 Human Visual System (HVS) (1) Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 4 HVS (2) • Rods and Cones excited by electromagnetic energy in the range 350-780 nm • Sizes of rods and cones determines the resolution of HVS – our visual acuity • The sensors in the human eye do not react uniformly to the light energy at different wavelengths Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 5 HVS (3) - Human Fovea 125 million Rods/eye Only 5-7 million Cones/eye Rods are 1000 times more sensitive to light Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 6 HVS (4) • Three different cones in HVS: • Blue, green & yellow – often reported as red for compatibility with camera & film • Transducin is a protein that resides in the retina and is able to effectively convert light energy into an electrical signal. Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 7 HVS (5) - Rod Cells Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 8 Vision (1) • Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus • Resolution: our ability to discern separate pixels on a display depends: • display resolution • display size a. b. • distance from it. Average is ~ 1' (minute of arc, 1/60 of degree) • Example: • 1' at reading distance 25 cm = 350ppi (pixels per inch). • iPhone 4 "Retina Display” • 3.5" display with 640×960 resolution = 326ppi Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 9 Vision (2) • Size and depth • visual angle indicates how much of view object occupies (relates to size and distance from eye) • visual acuity is the ability to perceive detail (limited) • familiar objects perceived as constant size (in spite of changes in visual angle when far away) • cues like overlapping help perception of size and depth • Brightness • subjective reaction to levels of light • affected by luminance of object • measured by just noticeable difference • visual acuity increases with luminance as does flicker • Colour • made up of hue, intensity, saturation • cones sensitive to colour wavelengths • blue acuity is lowest • 8% males and 1% females colour blind Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 10 Reading • Several stages: "Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, • visual pattern perceived it deosn't mttaer in waht oredr the ltteers in a wrod • decoded using internal representation of are, the olny iprmoatnt tihng is taht the frist and lsat language ltteers be at the rghit pclae. The rset can be a toatl • interpreted using knowledge of syntax, mses and you can sitll raed it wouthit porbelm. Tihs is semantics, pragmatics bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe." • Reading involves saccades and fixations • Perception occurs during fixations • Word shape is important to recognition • Negative contrast improves reading from computer screen Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 11 HVS Deficiencies & Limitations Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 12 Color – Trichromacy, Dichromacy • Normal cones and pigment sensitivity enable an individual to distinguish all the different colors as well as subtle mixtures of hues - normal color vision is known as trichromacy. • Dichromacy, a form of color blindness, or color deficiency, occurs when one of the pigments is seriously deviant in its absorption characteristics. • Protanopia – missing L • Deuteranopia – missing M (red-green) • Tritanopia – missing S Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 13 Color Deficiencies Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 14 HVS Limitations • In human vision, a significant degree of image processing takes place in the brain • 1 million myelinated optical nerve fibers carry the information from 125 million rods and 5-7 million cones to the brain • The retina is also involved in a wide range of processing tasks • Multiple processes in the brain in parallel • edge sharpening • contrast enhancement • spatial summation • noise averaging • other forms of signal processing that have not yet been discovered. • Optical limitations: • Illusions due to factors like retina memory • may conceal 2D/3D visualization system technical limitations Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 15 Color Perception – Limitation From 100.000 to 10 million (subjective) Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 16 HVS Optical Illusions Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 17 Optical Illusions - Interpreting the Signal • The visual system compensates for: • movement • changes in luminance. • Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 18 Perception – Optical Illusion Retina adaptation to neighboring color Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 19 Perception – Optical Illusion (1) How many colors ? Only 3 pink, white, green When the green and pink colors are placed side by side, they enhance each other’s darker tones, making them look like completely new colors. Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 20 Perception – Optical Illusion (2) Retina memory Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 21 Perception – Optical Illusion (3) Are the horizontal lines parallel or do they slope? Because we are trying to rationalize either the black vertical lines or white vertical lines, we cannot make sense of the untidiness of the columns and, to our eyes, the horizontal lines are sloping downwards Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 22 Perception – Optical Illusion (4) Concentric Circles Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 23 Perception – Optical Illusion (5) How many legs ? Flat 2D picture but the brain tries to make it 3D Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 24 Perception – Optical Illusion (6) Static/Dynamic ? Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 25 Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 26 Outline • Human Visual System • Components • Limitations/Deficiencies • Optical Illusions • Light and Colors • Light Properties • Artificial Light Sources • Color Models • 3D Visualization Systems Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 27 Light & Color Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 28 Physics of Light Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 29 Light + Eye = Colors • Light is a form of electromagnetic radiation • Visible spectrum 350 – 780 nm • No light => no color (proves the importance of the light rendering system in computer graphics) Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 30 Light & Color • Color is the perceptual characteristic of light described by a color name. • Specifically, color is light, and light is composed of many colors—those we see are the colors of the visual spectrum: red, orange, yellow, green, blue, and violet. • Objects absorb certain wavelengths and reflect others back to the viewer. We perceive these wavelengths as color. • A color is described in three ways: • by its name (hue), • how pure or de-saturated it is • its value or lightness. Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 31 Light can Do … • Reflection Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 32 Light Source Reflection (GBR) Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 33 Light can Do • Refraction Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 34 Light can Do … • Diffraction Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 35 Shadows • Can improve the realism • Illustrates spatial relationships among objects • Soft Shadows • Made by area light • Umbra – totally blocked from the light source • Penumbra – partially blocked from the light source • Can be modelled by a collection of point light sources Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 36 Measuring Light • Light is measured with two main alternative sets of units: • radiometry consists of measurements of light power at all wavelengths • photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception (to quantify illumination intended for human use). Felix G. Hamza-Lup, Ph.D - Fulbright Specialist 2013 (Thailand) 37 Measuring Light - Radiometry Felix G. Hamza-Lup,
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