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Simulating Real Paint: A Non-Photorealistic Approach. Reynold Bailey. Outline. Motivation Statement of Problem Previous Work Techniques Results Challenges and Future Work. Motivation. void ShapesUI::resize(int width, int height) { glViewport(0, 0, width, height);

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Simulating Real Paint:

A Non-Photorealistic Approach

Reynold Bailey


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Outline

Motivation

Statement of Problem

Previous Work

Techniques

Results

Challenges and Future Work

Washington University in St. Louis

Media & Machines Lab


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Motivation

void ShapesUI::resize(int width, int height) {

glViewport(0, 0, width, height);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluPerspective(60, (GLfloat) width /(GLfloat) height, 0.1, 4.0);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

gluLookAt(0.0, 0.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

}

void ShapesUI::draw() {

glClear(GL_COLOR_BUFFER_BIT);

switch (display) {

case DISPLAY_WIREFRAME: {

glDisable(GL_LIGHTING);

glPolygonMode(GL_FRONT, GL_LINE);

glColor3f(0.0f, 0.0f, 0.0f);

} break;

case DISPLAY_FLAT_SHADING: {

glEnable(GL_LIGHTING);

glPolygonMode(GL_FRONT, GL_FILL);

glColor3f(1.0f, 1.0f, 1.0f);

glShadeModel(GL_FLAT);

Washington University in St. Louis

Media & Machines Lab


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Motivation

Contrast control in Photoshop

Artist use of contrast

Washington University in St. Louis

Media & Machines Lab


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Problem Statement

“Simulating Real Paint Blends and Variations”

Exploration of techniques to capture, analyze and manipulate data from actual paint samples.

Exploration of techniques to apply captured “paint” to a 3D computer generated model.

Washington University in St. Louis

Media & Machines Lab


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Current Color Representation and Use

RGB color space

Hardware oriented

Difficult to pick and name colors

Uniform colors - no method for specifying statistical variation.

HSV color space

User oriented – Based on artistic notion of tint, shade and tone

Easier to pick colors

Uniform colors - no way to specifying statistical variation.

Washington University in St. Louis

Media & Machines Lab


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Previous Work

Color Palette Plug-in for Adobe Illustrator

Anne Spatler Brown University

Barbara Meier Brown University

The Lit Sphere: A Model for Capturing NPR Shading from Art

Peter-Pike J. Sloan Microsoft Research

William Martin University of Utah

Amy Gooch University of Utah

Bruce Gooch University of Utah

Washington University in St. Louis

Media & Machines Lab


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Previous Work: Color Palette Plug-in

Simulate a real artist’s palette

Select initial colors

Create blends by drawing a line between colors.

Use colors from the generated blends.

Provide automated palettes

Washington University in St. Louis

Media & Machines Lab


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Previous Work: The Lit Sphere

Typical example of a shading study

Easily transferred to computer graphics: (Paint by normals)

Washington University in St. Louis

Media & Machines Lab


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Previous Work: The Lit Sphere

The Lit Sphere approach:

Capture shading model from existing art and store the shading information on a sphere

Use the captured shading information to shade other models (application of paint by normals).

Washington University in St. Louis

Media & Machines Lab


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Previous Work: The Lit Sphere

The Lit Sphere Results

Washington University in St. Louis

Media & Machines Lab


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Color Blending in Real Paints

Red – Green Blend Using RGB

Red – Green Blend Real Paints

Washington University in St. Louis

Media & Machines Lab


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Data Capture - Histogram Representation

Count

0

1

Intensity

Washington University in St. Louis

Media & Machines Lab


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First Steps

Washington University in St. Louis

Media & Machines Lab


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Histogram Shifting Technique

System limited by number of samples scanned.

Store average RGB for all generated histograms.

Given desired RGB, search for closest histogram.

Shift each bin within that histogram to obtain a new histogram.

RGB (new bin) = RGB (old bin) + (Desired RGB – Average RGB (old hist))

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Traditional Approach

Each object in scene is assigned a single color

Scale color by:

^

^

^

n

^

I = < N , L > + < R , V >

Diffuse

Specular (optional)

N

L

R

V

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

+

dark

light

=

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

Artists paint in layers

Under painting – Represents the overall desired tone of the scene.

Base painting – Paint all objects in desired color.

Highlights – Add highlights and details to enhance painting.

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

Under paint

Base paint

Highlights

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

Composite Image

Highlights – Blend base paint and highlights.

^

^

< R , V > > 0

Under painting – Blend base paint and under paint.

^

^

- < N , L > > 0

All other regions – Display the base paint.

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

Highlights

Composite Image

Under paint

Base paint

Washington University in St. Louis

Media & Machines Lab


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3D Rendering – Our Approach

Washington University in St. Louis

Media & Machines Lab


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Challenges

Achieved color coherency with scanned paint samples.

Not achieved spatial coherency.

Only first order statistics collected from paint samples.

Washington University in St. Louis

Media & Machines Lab


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Possible Solutions / Future Work

Capture Texture in addition to color.

Stretching the sample to fit the surface. May distort brush strokes.

Frame to frame coherency.

Washington University in St. Louis

Media & Machines Lab


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Spatial Coherency - First Attempts

Washington University in St. Louis

Media & Machines Lab


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Demo

Washington University in St. Louis

Media & Machines Lab


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Questions ??

Washington University in St. Louis

Media & Machines Lab


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