Download presentation

Presentation is loading. Please wait.

Published byLeah Campbell Modified over 2 years ago

1
Philip Willis Projective Alpha Colour Media Technology Research Centre, University of Bath

2
1.Digital compositing and alpha 2.Projective geometry 3.How they come together Overview of Talk Media Technology Research Centre, University of Bath

3
Porter and Duff 1984 Opacity, alpha: (r, g, b, ), Digital Compositing Media Technology Research Centre, University of Bath

4
Porter and Duff 1984 A over B C= = Digital Compositing Media Technology Research Centre, University of Bath

5
Porter and Duff 1984 A over B C= A C A + (1 – A ) B C B = A + (1 – A ) B Digital Compositing Media Technology Research Centre, University of Bath B CBCB

6
Porter and Duff 1984 A over B C= A C A + (1 – A ) B C B = A + (1 – A ) B Digital Compositing Media Technology Research Centre, University of Bath CBCB B CACA A

7
Porter and Duff 1984 A over B C= A C A + (1 – A ) B C B = A + (1 – A ) B Digital Compositing Media Technology Research Centre, University of Bath CACA A CBCB B 1 - A

8
Porter and Duff 1984 Pre-multiplied colours C= A C A + (1 – A ) B C B = c A + (1 – A ) c B Digital Compositing Media Technology Research Centre, University of Bath

9
Homogeneous Coordinates Media Technology Research Centre, University of Bath Unify rotation, translation, scaling. Why? 4 by 4 matrices.

10
Projective Transformations Media Technology Research Centre, University of Bath

11
Projective Geometry Media Technology Research Centre, University of Bath Projective (wx, wy, wz, w) … normalises to give Euclidean: (x, y, z, 1) The w coordinate is the scale of the projective space.

12
1D Projective Geometry (x,w) Media Technology Research Centre, University of Bath

13
1D Projective Geometry (x,w) Media Technology Research Centre, University of Bath

14
2D Projective Geometry (x,y,w) Media Technology Research Centre, University of Bath

15
Projective Geometry and Colour Media Technology Research Centre, University of Bath 1. (wx, wy, wz, w) … projective (x, y, z, 1) … normalised 2. ( r, g, b, ) … premultiplied (r, g, b, 1) … normalised

16
Projective Alpha Colour Media Technology Research Centre, University of Bath (r, g, b, ) r, g, b are measures of energy. They are unbounded i.e. not just in [0.0, 1.0]

17
Projective Alpha Colour Media Technology Research Centre, University of Bath (r, g, b, ) is a measure of scale: area. It is unbounded i.e. not just in [0.0, 1.0]

18
Projective Colour Space Media Technology Research Centre, University of Bath

19
Projective Colour Space Media Technology Research Centre, University of Bath

20
Projective Colour Space Media Technology Research Centre, University of Bath

21
Projective Colour Space Media Technology Research Centre, University of Bath

22
Projective Colour Space Media Technology Research Centre, University of Bath

23
Pre-multiplied colours? Media Technology Research Centre, University of Bath Non pre-multiplied colours?

24
Colours as (r, g, b, ) vectors Materials as 4 by 4 projective transformations Materials transform colours Colour Transformations Media Technology Research Centre, University of Bath

25
Blend materials by blending matrices: matrix multiplication or matrix addition Colour mixing, illumination, filtering etc. Colour Transformations Media Technology Research Centre, University of Bath

26
Fluorescence Translation: colour offset Colour rotation Scaling: change area of material Colour vanishing points. Colour Transformations Media Technology Research Centre, University of Bath

27
Correct colour filtering Correct illumination effects Back-illumination too. Subtractive colour (C,M,Y) Correct perspective shading Some Benefits Media Technology Research Centre, University of Bath

28
Spectral rendering with one alpha value Volume rendering Unbounded energy and alpha Any colour calculations Some Benefits Media Technology Research Centre, University of Bath

29
Example: Filtering/Illumination Media Technology Research Centre, University of Bath

30
Example: Filtering/Illumination Media Technology Research Centre, University of Bath

31
Philip Willis Thank you! Projective Alpha Colour Media Technology Research Centre, University of Bath

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google