Reviewed paper:
WYSIWYG
NPR: Drawing Strokes Directly on 3D Models
Ideas
for a tutorial:
Strokes
How to create strokes
-
silhouette
lines
-
crease
lines
-
decal
strokes
-
structured
/ free / mobile hatching
Stroke
visibility
Real-time
algorithms for stroke generation
Media
How to
simulate types of natural media
-
watercolour
-
clay
-
….
Assigned topic:
Literature:
A. Lake, C. Marshall, M. Harris and M. Blackstein, Stylized rendering techniques for scaleable real-time 3D animation, Proceedings of SIGGRAPH 97, p.415-420
P.-P.J. Sloan, W. Martin, A. Gooch and B.
Gooch, The Lit Sphere: A Model for Capturing NPR
Shading from Art, SIGGRAPH
N. Halper, S. Schlechtweg and T. Strohthotte, Creating Non-Photorealistic
Images the Designer’s Way, SIGGRAPH
L. Streit, O. Veryovka and J. Buchanan, Non-photorealistic Rendering Using an Adaptative Halftoning Technique,
SIGGRAPH
J. Claes, F. DiFiore, G. Vansichem. F. Van
Reeth, Fast 3D Cartoon Rendering with Improved
Quality by Exploiting Graphics Hardware, SIGGRAPH
A.Gooch, B.Gooch, P.
Shirley and E.Cohen, A
Non-Photorealsitic Lighting Model for Automatic Technical Illustration, In:
Computer Graphics, July 1998, ACM Siggraph ’98 Conference Proceedings
T. Akenine-Möller and E. Haines, Real-Time Rendering 2nd
edition, A.K.
Peters Ltd, 2002
B. Hogarth, Dynamic Light and
Shade, Watson-Guptill
Plublications, New York, 1981
The tutorial’s content:
-
short
Introduction to NPR (Lake, p.1)
-
introduction
to shading and cartoon shading (before – after images as examples) (Lake, p.2)
-
rendering:
real-time vs. raytracing -> the approach (explanation: Lake, p.3)
-
current
OpenGL specification is not sufficient (Lake, p.3) -> see algorithm and
calculations (Lake, p.3)
-
problems:
colour quantisation or texture-mapping can lead to stair-case effects or too
fuzzy-borders (Claes, p.1) “Higher levels of antialiasing produce better results. Insufficient
antialiasing is particularly noticeable where ink lines are drawn: the lines
chatter during animation (in some cases, the lines show the dreaded
"jaggies").”
-
resolved
by subdivision of border pixel (Claes,
p.2)
-
potential
limitation: tone and texture are mixed (Streit, p.2)
-
variations
and the resulting effects: double source lighting, shadow-and-highlight
-
derived
style: pencil sketch shading
-
the
real cartoon-style: shading combined with stylistic inking (silhouettes) and
motion lines
-
remark
on implementation: HijackGL as possibility to overcome OpenGL limitations (http://www.cs.wisc.edu/graphics/Gallery/HijackGL/)
How-to
design a tutorial
When using chapters
and lessons or a similar format, users may sometimes want to have their current
location identified.
Begin each chapter
and each lesson with an objective, the general or particular information that
the user will (hopefully) learn.
Since scripts serve
people with varying degrees of computer proficiency, break information into
digestible sections. Make each separate action a distinct sentence. Avoid
run-on sentences.
Set an upper limit
to the amount of text you put on each page that does not contain internal
links; somewhere between 300 and 600 words per page is reasonable. You should
decide on a specific number based on your audience, your content, and how the
text fits into our overall design. Research has shown that a few long,
scrollable pages on a single topic are easier to download and print than
several short pages.
Studies have concluded that web surfers are more likely to read more of a page with several short paragraphs, than if the same content was contained in a few long paragraphs. Break up paragraphs with a line break, and not by indenting the new paragraph.
Although consistency
is important in all design, it's especially important in Web design. Because
one mouse click can send someone to a new section instantly, a consistent style
provides visual cues to let people know where they are.