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

Original Colour deficient simulation (orig)

Corrected Colour 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

Munsell NCS

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