Space, Time & Colour in Visualisation Space –Cues: position, size, overlay, colour, perspective, texture, lighting, focus, accommodation, convergence, stereoscopy. 3D on 2D. Semantic spaces Time –Snapshot, vectors, time series (graphs), animation, multi-layered Colour –Physics, colorants, illumination, perception, attention, motion, categorisation, emotion

Space – overview Real space (3D) Pictorial or illusory space Space perception active, supporting action Visualisation of 3D space on 2D based on depth cues (Why) is our perception of space three dimensional?

Space – position Relative horizontal order Relative height

Space – relative size Relative size among objects Relative size among areas (figure / ground) When are smaller objects closer to the viewer?

Space – familiar size Size perception based on familiarity What happens when relative and familiar sizes conflict?

Space – shape Skewed shaped according to linear perspective How do we discern unknown shapes from their orientation?

Space – Interposition Occlusion (overlap) Translucency (< 100% transparency) When are object edge lines needed when are they not?

Space – Edge interpretation Orientation & depth Illumination & reflectance What happens when there is no physically possible interpretation?

Space – colour Relative saturation (chroma contrast) Relative lightness (luminosity contrast) Does colour / luminosity constancy affect space perception?

Space – convergence of parallels Linear perspective projection Brunelleschi, Santo Spirito church, 1436

Space – texture Texture gradient Gustave Caillebote, Paris Street: Rainy Day

Space – lighting (shadows) Shadows diffuse shading cast shadows

Space – lighting (highlights) Highlights

Space – lighting (reflections) Reflections

Space – focus Depth of focus Why does video not look as 3D as film (look at DOF)?

Space – accommodation Changing eye lens size in order to focus

Space – accommodation Lens accommodation in the eye Why does accommodation not destroy 3D on 2D illusion?

Space – convergence Convergence of eyes Are there problems of convergence with 2D computer displays?

Space - stereopsis Binocular disparity and fusion of images What does fusion do to one’s depth perception?

Space – kinetic Use of body enhanced depth perception What happens to space perception if you don’t move at all?

Time - overview Normative time (seconds, minutes, hours) Experienced time (psychological, real life) Implied or imaginary representation of time (on a 2D surfaces) Visualisation concerned with implied time and different representations of time Visualisation can offer insights into normative time which can’t be experienced

Time – snapshot A point in time with a history and future Dust clouds near North African deserts

Time – diagrammatic Vector map - movement, velocity, direction and path in time Vector fields displaying fluid movement

Time – time series graphs Time series (plotted X-Y graphs) An image embedded into sound (sonogram) A flux of x-rays plotted against time

Time – sequence Succession of snapshots When does motion become fluid and flicker unnoticeable? Hydrogen atom superposition of 6 eigenstates

Time – narrative & symbolic Jerusalem 3000: Three Millennia of History

Colour – overview Light is electromagnetic radiation Colour is a perceptual property of light Light wavelengths do not map directly to colours Colour of an item is a combination of item, lighting and viewer characteristics Human colour vision is corrective, can be fooled and has strong emotive impact

Colour – physics Electromagnetic radiation Why do we not see other frequencies of the EM spectrum?

Colour – Colorants Pigments and dyes absorb & reflect different frequencies What is the real colour of an object (how to measure)?

Colour – illumination Illumination has a spectral distribution What is ”daylight” and what is its colour temperature?

Colour – illumination intensity Light intensity affects colour vision! How can you calibrate displays if intensity affects colour vision?

Colour – perception Perception = object properties + illumination properties (both global and local) + perceiver properties

Colour - deficiency Deficiency in separating hues OriginalColour deficient simulation (orig) CorrectedColour deficient simulation (corrected) What is normal colour vision if everybody sees differently?

Colour – attention Colour guides visual attention (pre-attentive) What other pre-attentive vision properties are there?

Colour – motion Colour can cause apparent motion

Colour - categorisation Various colour models for diff. purposes MunsellNCS Why don’t we define colours via their spectral distribution?

Colour – emotion Colour’s emotive impact is relative –Culture –Size in visual field –Saturation –Surrounding colours –Personal differences –Genre –Etc. Why does colour have such a potential emotional impact?

Summary Space, time and colour are related: Visualization is about sensing, decoding and representing with space, time & colour Many things in vision unknown Opportunities for research and experiments