+ All Categories
Home > Documents > To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional...

To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional...

Date post: 01-Oct-2020
Category:
Upload: others
View: 3 times
Download: 0 times
Share this document with a friend
48
To understand Leonardo da Vinci drawings using 3D techniques Marco Gaiani, Fabrizio Ivan Apollonio, Roberta Barsanti, Roberto Palermo 8 MAY 2019 – RIJKSMUSEUM, AMSTERDAM Alma mater studiorum A.D. 1088 Università di Bologna
Transcript
Page 1: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

To understand Leonardo da Vinci drawings

using 3D techniques

Marco Gaiani, Fabrizio Ivan Apollonio, Roberta Barsanti, Roberto Palermo

8 MAY 2019 – RIJKSMUSEUM, AMSTERDAM

Alma mater studiorum A.D. 1088

Università di Bologna

Page 2: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

2

Introduction

Working group

Alma Mater Studiorum – University of Bologna

Fabrizio Ivan Apollonio, Giovanni Bacci, Andrea Ballabeni, Marco Gaiani,

Simone Garagnani

Gallerie degli Uffizi - Florence

Roberto Palermo

Museo Leonardiano - Vinci

Roberta Barsanti

Relio

Marco Bozzola

Page 3: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

3

Introduction

Outline

The problem

Fine drawings visualization, understanding and analysis

The solution

New application to analyze drawings as graphic artifacts

ISLe – InSightLeonardo

Development 2011-2019

Case study

Leonardo da Vinci drawings

Page 4: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

4

Case study

Study of human body proportionsKnown as

The Vitruvian man

Pen and ink with wash over metalpoint on white paper,

345x246 mm

Gabinetto Disegni e Stampe, Gallerie

dell’Accademia, Venice

Recto

In partnership with:

Acquisition 2014

Probably the most famous existing drawing

Page 5: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

5

The back of the drawing unveils the copying work of

the painter Giuseppe Bossi at the beginning of the XIX

century

Verso

Case study

Study of human body proportionsKnown as

The Vitruvian man

Page 6: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

6

Case study

Landscape, 5 August 1473

Pen and two colors of brown

iron gall ink, red chalk, lead tip

on paper 196 x 287 mm., 1473

Gabinetto Disegni e Stampe

degli Uffizi, Florence, inv. 8P

Recto:

Landscape of the Arno River

and Valley and Marmore

waterfall

Acquisition 2018

Page 7: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

7

Case study

Landscape, 5 August 1473

Pen and two colors of brown

iron gall ink, red chalk, lead tip

on paper 196 x 287 mm.

Gabinetto Disegni e Stampe

degli Uffizi, Florence, inv. 8P

Verso:

Landscape, man running,

some geometric figures

Page 8: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

8

Case study

Study for the Background of the Adoration of the Magi

Metalpoint, pen and brown ink,

brush and brown wash, traces

of white gouache highlights,

over stylus and compass

construction, pinpricks for

measurement, 163 x 290 mm.

Gabinetto Disegni e Stampe

degli Uffizi, Florence, inv.

436E

Recto

Acquisition 2018

Page 9: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

9

Leonardo da Vinci, The Adoration of the Magi

Unfinished painting. Oil and some tempera

grassa on wood, 246×243 cm, 1481-1482

Galleria degli Uffizi, Florence

Case study

Study for the Background of the Adoration of the Magi

Page 10: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

10

Case study

Study for the Background of the Adoration of the Magi

Metalpoint, reworked with pen

and brown ink, brush and

brown wash, traces of white

gouache highlights, over stylus

and compass construction,

pinpricks for measurement, 163

x 290 mm.

Gabinetto Disegni e Stampe

degli Uffizi, Florence, inv.

436E

Verso

Page 11: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

11

The new application

ISLe - InSightLeonardo

GoalTo improve tracings and hatchings analysis to understand the artist

graphic method and the drawing features

MethodExperience the drawing as if it were in your hands

OutputDigital copy of the physical drawing perceptually indistinguishable

from the original & manipulable using gestures

TargetScholars and exhibition & museums visitors

Solution

Acquisition, real-time rendering & interaction

of the drawing’s total appearance

Page 12: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

12

ISLe background

Main observations

The spectrum of colors in a drawing is

much narrower than the spectrum of

colors in a painting

Multispectral techniques not offer

significant advantages

No advantages for tracing

definitions

Color gamut

Colorimetric reproduction

Page 13: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

13

ISLe background

Main observations

Thickness left by pens and pencils 5÷10 μm

Laser scanner techniques are not effective (max lateral spatial

resolution possible 50-60 μm)

CG simulation of

surface features from

images

The Vitruvian Man

Depth information

Page 14: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

14

ISLe background

Main observations

Appearence structure modeling

Macrostructure (polygons)

Mesostructure (small details and bumps)

Microstructure (light reflection orientation)

S.H.Westin, J.Arvo, K.E.Torrance, Predicting reflectance functions from complex

surfaces, 1992

Page 15: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

15

ISLe

Workflow features – three modules

ACQUISITION

• SHAPE

• COLOR

• BRDF

1. Accurate and safe on-site image capture of drawing shape and surface

reflectance with a faithful 3D reconstruction of its features

Page 16: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

16

ISLe

Workflow features – three modules

ACQUISITION

• SHAPE

• COLOR

• BRDF

VISUALIZATION

• VIEWER

• RENDERING

• VISUALIZATION DEVICE

2. High fidelity real-time rendering of the total appearence of the drawing:

resolution of 50 mm; accurate color reproduction on a 100% sRGB capable display

Page 17: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

17

ISLe

Workflow features – three modules

ACQUISITION

• SHAPE

• COLOR

• BRDF

VISUALIZATION

• VIEWER

• RENDERING

• VISUALIZATION DEVICE

INTERACTION

• INTERACTION DEVICE

• INTERACTION TECHNIQUES

• ADDED TOOLS

• SEMANTIC INFORMATION ORGANIZATION

3. Adaptation of traditional multitouch interaction paradigm to fit the exploration

of 2D-3D contents to minimize uncommon gestures

Page 18: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

18

Developed workflow

Data capture

1. System characterization

2. Resolution characterization

3. Color correction

4. Image post-processingCIEXYZ to sRGB

Sharpen

Camera selection Sensor quality

Noise measurement

Light selection &

positioning

Target 18% Light uniformity

ISO 12233 MTF test

X-Rite CC

CIEXYZ color space

Color correction

Color accuracy

Page 19: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

19

Developed workflow

Resolution required 8000 x 5500 pixels

Color quality required: 48-bit depth

Large format scanning back based Rencay

DiRECT Camera System 24k³

Sensor: trilinear ON semiconductor 8000 CCD

Maximum optical resolution: 8000 X 13000 pixels

Maximum resolution: 24000 X 39000 pixels

Color depth: 48 bit

Pixel size: 9 μm (H) x 9 μm (V)

Resolution limit: 55 lp/mm with contrast > 60%

Sensor area: 72 x 118 mm

Capture device

Chip back Scan back

Page 20: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

20

Developed workflow

Lighting system – 2014 solution

Four Osram Studioline L-55W fluorescent continuous lights

CCT 5600°K

Operating temperature 22°C

Luminous Flux 3800 lm

Output Color Rendering Index (CRI) 85%

Spectral power distribution (SPD)

Presence of frequencies in which the response is limited

UV internally used to excite the phosphors, could be source of damaging UV

Page 21: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

21

Developed workflow

Lighting system – 2018 solution

16 High Flux single LED white light Relio2

CCT 4000°K

Operating temperature: 20°C

Luminous Flux 430 lm

Output Color Rendering Index (CRI) > 95%

Spectral power distribution (SPD)

Continuous spectrum of visible light

No IR & UV wavelengths light components

Page 22: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

22

Developed workflow

Lighting system – 2018 solution

Relio LED solution advantages

- Light spectral properties are consistent from shot to shot and year to year

- Lumens/watt is stable

- Low power and consumption

- Limited weight (2,5 kg whole system)

- Quick setup and limited space required

Page 23: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

24

Developed workflow

Evaluation of the levels of illumination during the photoshot

2014 solution - Four Osram Studioline L-55W fluorescent continuous lights

Results

2018 solution - 16 High Flux LED white light Relio2

Page 24: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

25

Developed workflow

Five Rules of Colorimetric Imaging

(1) Lighting correlated color temperature (CCT) near 5000 K (D50 workflow)

(2) Optimal exposure

(3) Profile based on minimizing ∆E with outstanding lightness accuracy

(4) Independent validation using target not used for camera profiling

(5) Encoding space does not clip scene colors

Roy Berns

Scientific Imaging of Cultural Heritage: Minimizing visual editing and relighting

2+3D Photography Practice and Prophecies, 2015

Same target used for calibration

+

Expert observers judgment

Page 25: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

26

Developed workflow

Color correction - SHAFT (SAT & HUE Adaptive Fine Tuning)

Features

- Target based technique

- Based on Bruce Fraser's calibration procedure for successive approximations

from RAW images (ACR-scripts)

- Developed in MATLAB supported by DCRaw

(www.cybercom.net/~dcoffin/dcraw/)

- CIEDE2000 colour-difference formula to evaluate color error

- Usable alone or coupled with a polynomial regression

M. Gaiani, A. Ballabeni, SHAFT (SAT & HUE Adaptive Fine Tuning), a new automated

solution for target-based color correction, 2018

Gaiani et al., “Securing Color Fidelity in 3D Architectural Heritage Scenarios”, 2017

Page 26: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

27

Color correction

Target selection

(1) to establish accurate color image capture - part of a calibration function

(2) to evaluate deviation from the desired capture of color image information

X-Rite ColorChecker Classic

Full Size: 8.5”x11”

24 Patches - 6 Neutral Gray

Problem

CC for subjects predominated by near neutrals and limited color

Typical solution

collection-specific color test targets

TrialsDon Williams, Targeting for Important Color Content: Near Neutrals and Pastels, 2012

Unstable results

Candidate colors selection is not easy and can lead to even greater errors

Solution based on observer judgement & weighted version of SHAFT

to better fit color existing in the drawings

Judgment on results of differently weighted CC images against the drawing and a

manually CC image on different monitors & room lighting condition

Page 27: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

28

Color accuracy & exposure evaluation

Results - Florence (no weights)

Mean color accuracy ΔE*00 = 2.31

Mean lightness accuracy ΔL*00 = 0.59

Exposure error 0.02 f-stop

Page 28: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

29

Results - Florence (weighted)

Mean color accuracy ΔE*00 = 2.25

Mean lightness accuracy ΔL*00 = 0.63

Exposure error 0.00 f-stop

Color accuracy & exposure evaluation

Page 29: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

30

Developed workflowDeveloped workflow

Resolution characterization - ISO 12233:2000

MTF results - Florence

Average spatial resolution (horizontal)

▪ Rising edge distance of 10-90% = 4.76 pixels

▪ MTF50 = 0.179 line pairs/pixel

▪ MTF10 = 0.452 line pairs/pixel

▪ Effective resolution: 575 Px/inch finer

detail of 75 µm

Requirements

Leonardo tracing of a minimum of 90 µm thick

565 ppi are needed

Page 30: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

31

Developed workflow

Material modeling – Macroscale

Surface shape

Assimilated to a polygonal plane (16384 triangles)

Page 31: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

32

Developed workflow

Material modeling - Mesoscale

Multitexture method with four map

▪ Albedo

▪ Normals

▪ Depth

▪ Specular

Page 32: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

33

Developed workflow

Material modeling - Mesoscale

Normal map reconstruction: photometric stereo techniques

Four Light Imaging

4 images with constant illumination from 4 directions, ≈orthogonal to each other

Solution implemented

B.D. Cox & R.S. Berns, Imaging artwork in a studio environment for

computer graphics rendering, 2015

Page 33: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

34

Developed workflow

Material modeling - Mesoscale

Normals reconstruction: results

Page 34: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

35

Developed workflow

Material modeling - Mesoscale

Normals reconstruction: results

Improved

Cox & Berns

Old

technique

Page 35: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

36

Developed workflow

Material modeling – Mesoscale/Macroscale

Height map reconstruction

1. Gradient map reconstruction

2. Displacement in the normal direction of the drawing plane

Height map from uncorrect normal map

Problem

Normal map inaccuracies caused by

- not perfectly regular distribution of the lighting despite

the flat fielding regularization

- inaccuracies of the position measurements of the four

lights (i.e. violation of the condition of distant light)

Page 36: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

37

Developed workflow

Material modeling – Mesoscale/Macroscale

Height map reconstruction

Process

1. Lighting decay correction using the lightness channel on the gray card images

2. Normal map reconstruction using Cox & Berns technique on the correct images

3. Gradient map reconstructon using the Knald gradient operator, which allows to

minimize cumulative errors due to residual noise (https://www.knaldtech.com)

4. Displacement in the normal direction of the drawing plane

Displacement calibration

1. Conversion of the gradient map into a modeled surface using an algorithm that

follows an error minimization principle with Grasshopper & Kangaroo plug-in

2. Calibration against results of 3 test-case papersheet with shape configurations

similar to those of drawings reconstructed with automatic photogrammetry techniques

Height map from correct normal map

Accuracy achieved: 50 mm

Page 37: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

38

Developed workflow

Material modeling – Mesoscale/Macroscale Results

PhotoRendered

with Corona render

Study for the Background of the Adoration of the Magi

Page 38: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

39

Developed workflow

Material modeling - Microscale

Paper BRDF (Bidirectional reflectance distribution function) and shader

Inspired to M. Papas, K. de Mesa, H. W. Jensen, A Physically-Based BSDF for

Modeling the Appearance of Paper, 2014

Exploiting the Walt Disney physically-based shading framework

B. Burley, SIGGRAPH 2012 & 2015

Implemented in the Unity rendering engine system

www.unity3D.com

Page 39: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

40

Developed workflow

Material modeling - Paper BRDF

micro-surface

subsurface

retro-reflection sheen

diffuse

Paper modeled as material

- highly scattering

- optically thick

- which exhibits a combination of subsurface scattering, specular reflection,

retroreflection, surface sheen, and transmission effects

Page 40: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

41

Developed workflow

Material modeling - Paper BRDF

BRDF model

- Reflection & refraction: microfacet model of the rough glass (Walter et al., 2007;

Torrance & Sparrow 1967; Cook & Torrance, 1981)

- Subsurface scattering:

▪ A BSDF reduction of the (Donner & Jensen, 2005) multi-layer model based on

the assumption that the length of the mean free path is orders of magnitude

smaller than the thickness of paper and the spatial resolution of the sensor

▪ The single scattering theory of (Hanrhan & Krueger, 1993)

Page 41: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

42

Developed workflow

Material modeling results – Microscale

Old shader New shader

Paper

Page 42: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

43

Iron gall ink

Old shader New shader

Developed workflow

Material modeling results – Microscale

Page 43: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

44

Results

Landscape, 5 August 1473

Demo

Page 44: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

45

Whats happen?

Perfecto e virtuale

Exhibition

24 OCTOBER 2014 - 6 JANUARY 2015

Arco di Augusto - Fano

.20.000 visitors!The opening day

Paola Salvi in front to the table

Page 45: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

Paola Salvi, The Midpoint of the Human Body in the

Leonardo’s Drawings and in the Codex Huygens, 2016

Whats happen?

Perfecto e virtuale

One year later

Paola Salvi in front to the table

Page 46: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

Whats happen?

Leonardo a Vinci. Alle origini del genio

The opening day

Exhibition

15 APRIL 2019 - 15 OCTOBER 2019

Museo Leonardiano, Vinci

Page 47: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

Whats happen?

Leonardo a Vinci. Alle origini del genio

In print

Marco Gaiani, Fabrizio Ivan Apollonio, Giovanni Bacci, Andrea Ballabeni, Marco

Bozzola, Riccardo Foschi, Simone Garagnani, Roberto Palermo, Vedere dentro i

disegni Un sistema per analizzare, conservare, comprendere comunicare i disegni

di Leonardo, 2019

New insights on the Landscape, 5 August 1473, using ISLe!

Page 48: To understand Leonardo da Vinci drawings using 3D techniques · Paper BRDF (Bidirectional reflectance distribution function) and shader Inspired to M. Papas, K. de Mesa, H. W. Jensen,

49

Thank you for your attention!

Marco Gaiani [email protected]

Fabrizio Ivan Apollonio [email protected]

Roberta Barsanti [email protected]

Roberto Palermo [email protected]


Recommended