an individual perspective - perceptually realistic depiction …€¦ · · 2015-12-31an...

Lehrstuhl fürMediengestaltung

An Individual Perspective - Perceptually Realistic Depiction Of Human Figures

Martin Zavesky, Jan Wojdziak, Kerstin Kusch, Daniel Wuttig, Ingmar S. Franke and Rainer Groh

VISAPP 2011, 5. March - 7. March 2011

Fakultät Informatik, Institut für Software- und Multimediatechnik

This publication is supported by the European Union and the Free State of Saxony, funded by the European Social Fund (ESF)

Übersicht

Motivation

General approach

Multi-perspective solutions

OBPC

CBPC

Discussion

Study

Future work

Conclusion

Motivation

The common computer graphics camera model creates mono-perspective images.

Mono-perspective images do not fulfil the expectations of natural viewing behaviour [1].

Change of figures‘ proportion and orientation due to the projection

Fig. 1: Mono-perspective image, aperture angle 120 degree

General approach

Fig. 2: The Tribute Money, Tommaso di Ser Cassai (Masaccio), 1425-1428

Study of artistic solutions for projective problems

Especially study of human depiction in arts and computer graphics

General Approach

[S]

[P0] [PA]

[B][A]

[PB]

[H]

Fig. 3: Sketch of ’The Tribute Money’, Tommaso di Ser Cassai (Masaccio), horizontal [H] and sagittal [S] line, princi-ple vanishing point [P0], additional principle vanishing points [PA] and [PB] of persons [A] and [B]

Artists solved projective problems by using of multiperspective imaging.

Especially human figures were displayed with its own perspective. This leads to perceptual realism

Perceptual realism means to integrate the characteristics of human perception into the imaging process and the image.

Multi-perspective solutions

Multi-perspective imaging seems to be a valuable way

Non-photorealistic rendering shows an wide range of possible approaches

[2] [3]

[4] [5]

[6]

Fig. 4: Multi-perspective NPR solutions

OBPC

[OA]

[C]

[OB] [OC]

[DA] [DB] [DC]

[V]

[I]

Object based Perspective Correction

1. Specify the pivot point of the object in

the local camera coordinate system.

2. Compute the shear factors from that

relative position

3. Compute the rotation angles

4. Rotate the object around x- and y-axis

according to the rotation angles

5. Shear the object with a shear matrix

based on the computed shear factorsFig. 5: The system camera renders [OB], [OC] excluding the object [OA] attached to the object camera. For size constancy the

image plane [IA] of the object camera is shifted right up to the intersection [S]

OBPC





relative position





based on the computed shear factors

[A] [B][C][D]

a

bFig. 6: Monoperspective image (a), result of the OBPC on colored figures (b)

OBPC





relative position





based on the computed shear factors

CBPC

Camera based Perspective Correction

1. Create an object camera and assign an

object

2. Align viewing direction of the object

camera to the pivot point of the object

3. Translate image plane towards the object

4. Calculate original position of the object on

system image plane in screen coordinate

system

5. Translate the image to the position on the

final image

6. Sort image planes by depth

[OA]

[C]

[OB] [OC]

[IA]

[IB]

[V][VA]

[S]

Fig. 7: The system camera renders [OB], [OC] excluding the object [OA] attached to the object camera. For size constancy the image plane [IA] of the object camera is shifted right up to the intersection [S]

image of object camera image of system cameraresulting image

CBPC

Fig. 8: Composition of different views in the CBPC

CBPC

[A] [B][C][D]

a

b



object






system


final image


Fig. 9: Monoperspective image (a), result of the CBPC on colored figures (b)

CBPC



object






system


final image


Both approaches have individual advantages and disadvantages

Comparison

a b c

d e f

Fig. 10: Details: (a+d ) mono-perspective rendered with standard camera, (b+e ) using OBPC, (c+f ) using CBPC

Mono-perspective OBPC CBPC

Both approaches have individual advantages and disadvantages

Each approach complements the other

Both may be used parallel in scenes without interference

Discussion

advantages disadvantages

Object-BasedPerspectiveCorrection

Camera-BasedPerspectiveCorrection

unmodified camera

adjustable

objectintersection

no objecttransformation

no objectintersection

modifiedcamera

non-adjustable

transformationnecessary

Fig. 11: Comparison of OBPC and CBPC

Study

Study on the perception differences of mono- and multiperspective relative to the natural viewer perception

Examination of the real scene orientation of human figures and its perception by the viewer

First cognition: Difference between percieved an intended orientation

F1 F2

Fig. 14: Comparison of percived an intended figure orientation (orginal orientation -30 degree)

F1 F1

Fig. 12: Scene with rotated figures (-30 degree), mono-perspective image

Original orientation

Mono-perspective

Photo

OBPC

F1 F2

Fig. 13: Scene with rotated figures (-30 degree), multi-perspective image

Solve light and shadowing problems

Development of CBPC adjustabilty

Further research on orientation to determine ideal parameters of the algoritms to create perceptually realistic images

Future work

Conclusion

Perceptual realism could be achieved by multi-perspective images based on perspective projection enhanced by characteristics of visual perception and techniques of Renaissance painting.

OBPC and CBPC differ in its way of solving distortion and misalignment.Both approaches use multi-perspective imaging to adapt the image to the human viewing behavoiur.

This could enhance an adapted depiction og objects especially of human figures.

Thank you for your attention!

This publication is part of the inovation promotion of Martin Zavesky and Jan Wojdziak which is supported by the European Union an the Freestate of Saxony funded by the European Social Fund (ESF).

Questions andanswers

References

[1] I. S. Franke, S. Pannasch, J. R. Helmert, R. Rieger, R. Groh, und B. M. Velichkovsky, “Towards attention-centered interfaces: An aesthetic evaluation of perspective with eye tracking,” ACM Trans. Multimedia Comput. Commun. Appl., Bd. 4, S. 1-13, 2008.[2] D. Zorin und A. H. Barr, “Correction of geometric perceptual distortions in pictures,” in SIGGRAPH ‚95: Proceedings of the 22nd annual conference on Computer graphics and interactive techniques, S. 257–264, 1995.[3] P. Coleman und K. Singh, “Ryan: rendering your animation nonlinearly projected,” in NPAR ‚04: Proceedings of the 3rd international symposium on Non-photorealistic animation and rendering, S. 129-156, 2004.[4] P. Rademacher und G. Bishop, “Multiple center of projection images,” in Proceedings of the 25th annual conference on Computer graphics and interactive techniques, S. 199–206, 1998.[5] K. Singh, “A Fresh Perspective,” in Proceedings of Graphics Interface 2002, S. 17-24, 2002.[6] M. Agrawala, D. Zorin, und T. Munzner, “Artistic Multiprojection Rendering,” in Proceedings of the Eurographics Workshop on Rendering Techniques 2000, S. 125-136, 2000.

Standard projection Shearing Shearing and rotation

Standard projection Shearing Shearing and rotation

OBPC


Undistorted depiction of curved surfaced objects

Integration of multiple additional principle vanishing points

OBPC

Direct geometry manipulation

Rendering by standard cg camera model

Rotation an shearing depending on the realtion between camera and object

Shearing of rotated objects

Parts of OBPC

Y

Z

Y

Z

Y

Z

Rotation of objects

Original scene

Matrix notationPoint of object = [P]Corrected Point = [P’]

Transformation matrix of object = [O]Transformation matrix of object (modified) = [O’]

Transformation matrix of camera = [K]Transformation matrix of camera (modified) = [K’]

Relative position of the object to the camera = PO

Shearmatrix defined by shear factors = [S]Rotation relative to local z-axis = [Rz]Rotation relative to local x-axis = [Rx]

[P’] = [O’] * [K’] * [S] * [Rx] * [Rz] * [K’]-1 * [O’]-1 * [P]

[K] [K’][K’]-1

[O’]-1

[O’]

[P]

[O]

[P’]

PO [R ]X [R ]Z[S]

BerechnungEingabe

OBPC

Input

Calculation

OBPC

The more an object is located away fromt the optical axis [S] the more it is distorted.

Especially relelevant on objects with curved surface

Projection on the image plane

[O] Object[B] Image [E] Image plane[A] Center of Projection[GM] Principle vanishing point[S] Optical axis

OBPC

Modification of original geometry

Projection on the image plane with modified geometry

[O] Object[B] Image [E] Image plane[A] Center of Projection[GM] Principle vanishing point[S] Optical axis

Study

Study on the perception differences of mono- and multiperspective relative to the natural viewer perception

Examination of the real scene orientation of human figures and its perception by the viewer

First cognition: Difference between percieved an intended orientation

F1 F2

Comparison of percived an intended figure orientation (orginal orientation -30 degree)

F3

F1 F2 F1 F2

Scene with rotated figures (-30 degree), mono-perspective image (left), multi-perspective image (right)

Original orientation

Mono-perspective

Photo

OBPC

F1 F2

an individual perspective - perceptually realistic depiction …€¦ · · 2015-12-31an...

Documents