高级计算机图形学ACG05

高级计算机图形学Advanced Computer Graphics Advanced Computer Graphics Course No. 04814560

主讲教师：裴玉茹

Instructor: Yuru Pei

Email: peiyuru@ Email:peiyuru@cis pku edu cn Department of Machine Intelligence

Peking University

Peking University

Non-Photorealistic

Rendering

/~hxu/publications/index.html

Using a term like ‘nonlinear science’ is like

referring to the bulk of zoology as ‘the study

of nonelephant animals.

of nonelephant animals’

-Stanislaw Ulam

NPR’s applications NPR s applications

NPR s applications NPR’s applications

Outline •Toon Shading

(painting)

•Silhouette Edge

g(g)

Rendering(Inking)

•Other Styles

•Lines

T Sh di

Toon Shading •Toon Shading(cel

shading)

–The most popular

form of NPR

–Amplification

“Amplification

through

simplification”

-Understanding

Comics, McCloud

g

•How to do toon shading?

–Painting& inking

(shading&

silhouette rendering)

silhouette rendering

Most common methods for painting

Solid color Two-tone approach (hard shading)

Gouraud-shaded duck silhouettes rendered,

two tone shading specular/diffuse

with solid shading two-tone shading specular/diffuse three-tone

N li hti d l(t b d)

New lighting model (tone-based)•Traditional shading

Traditional shading

•Tone-based shading

New lighting model (tone-based) N li hti d l(t b d)

New lighting model (tone-based)

Black shaded regions hide details & some edge lines

Highlight and fine detail are lost in white shaded regions

N li hti d l(t b d)

New lighting model (tone-based) Colored Phong-shaded spheres with edge lines and highlights

C l d Ph h d d h ith d li d hi hli ht

Colored spheres shaded with hue and luminance shift, including edge lines and highlights

lines and highlights

g p

Shading method-1D texture map •Lake et al. and Lander’s shading method

use the idea of computing the diffuse shading dot product –use the idea of computing the diffuse shading dot product n•L –for each vertex and using n•L as a texture coordinate to access a 1D texture map p

g p

Shading method-1D texture map •Cartoon shading

Silh tt d i(I ki)

Silhouette rendering (Inking)•Different types of edges

Different types of edges

–boundary or border edge

•Edges not shared by two polygons

Edges not shared by two polygons

–crease or hard edge

•The dihedral angle is greater than some

threshold

•Further subcategorized into ridge & valley –material edge

t i l d

•The two triangles sharing it differ in material –silhouette edge

silhouette edge

•One triangle is front-face, and the other is

back-face