Computer graphics can be a powerful tool for supporting visual problem solving, and interactivity plays a central role in harnessing the users' creativity. This course will introduce various interactive tools developed in computer graphics research field with their design rationales and algorithms. Examples include enhancements to graphical user interfaces, authoring tools for 2D drawings and 3D animations, and interactive computer-aided design systems. Rich live demonstrations and course assignments will give you insights and skills to design and implement such tools for your own problems.
3-4 Flower Modeling
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Do curso por The University of Tokyo
Computação Gráfica Interativa
159 classificações
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3D Geometric Modeling
In this module, we rise up from 2D plane to 3D space, and discuss 3D geometric modeling methods. Topics introduced are; suggestive interface for architectural models, a sketch-based modeling system for freeform shapes, a curve-based shape control method, a flower modeling system, and volumetric texture. You will see how 3D objects can be easily and quickly modeled by specially-designed 2D user interfaces!
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Takeo IgarashiProfessor
Department of Computer Science, Graduate School of Information Science and Technology
And next topic is flower modeling.
This is an example of very domain specific modeling operations.
And the work we introduce here is called floral diagrams and inflorescences.
The program we present here, discuss here is
flower modeling, and the flower modeling is very difficult.
It has very complicated geometry.
With you know, petals and [UNKNOWN], and
also, at the same time, complicated structure.
So, again, each element has complicated shape, and also
we have a very complicated arrangement of interior elements.
So that's a program we want to address.
And our approach is like this, for complicated geometry
we use very specialized sketching interfaces for all our elements.
For hunting a complicated structure we
again, provide a very specialized structure editor.
By combing a very specialized system we can make it very
much easier for the user to design various kinds of flowers.
Let me show you a video.
So here's a program we would try to address.
You know, this kind of flower diagram, a flower
more that it consists of many small elements obligated together.
And then we have complete skeleton structure like this one, I like this one.
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And then what we do is use a traditional art of presentation called
floral diagrams, and inflorescences as an interface
for designing our flowers in the computer.
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So floral diagram, defines arrangements of elements for individual flower.
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Inflorescences defines an arrangement
or group of flowers in this model.
And you see the user interactivity operates the diagram,
and then you continuously see this updated to your directory
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And the modeling process start with the defining of a floral diagram.
So in the flower base you arrange individual elements,
and then you can see a 3-D measure preview here.
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So as you see, this is a
very specialized dedicated weathering system for flower arrangements.
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After our getting a diagram, now, the user defines a geometry.
As you see, we provide a very, very simple sketching interface for defining a shape.
But here, system will carry [UNKNOWN] off a resolution.
And for each, for our element, our
system provides a various indicated sketching apparatus.
So this is why in is initiating a pulse.
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And then this is texture modeling, so you draw three lines.
And then you get this after you get the 3-D model.
And from the side view the user draws a line, and you get a different shape.
So with just only four strokes, you will get a very huge form of flower element.
And you can continuously add more and more strokes, to get more detailed shape.
And then after having drawn a
diagram and 3D components, you establish correspondences,
or associations, and then with some information
assistance, start to generate an aggregated composition.
And then you will get, beautiful shape.
Now we assemble them together into a, structure using infrared tendencies.
You get this template, and then you change the shape, and then you label the shape.
And now we define axis, center axis by sketching.
This is an interesting part, so you draw two dimensional stroke to
define axis, and then system generates 3D minimum axis that we see.
This is the last stroke, and then as
the user draw, system would generate 3D dimensional axis.
And sometimes you finish drawing you can rotate
and you will get the reasonable 3D shape.
[BLANK_AUDIO]
Yeah, so here's a little bit more
description about 2D input to 3D stalk part.
So without depth assignment if you project your input onto
a flat surface it looks unnatural, a very flat shape.
However, with our algorithm.
User draws a stroke, two-dimensional stroke, and
the system automatically assigns a natural, naturally
looking depth variation, so if you look
from, look from a sideway, it looks natural.
So to do this, what we do is assume
that three-dimensional curvature is always constant in 3-D space.
Is this assumption we can look into the computer depths.
And then her are a couple results.
I think it is very tedious and time-consuming to generate
these types of models using traditional 3D general purpose modeling systems.
But with our system, it's very, much, much faster.
Of course, it takes certain time, but it's much faster than using creation method.
And you can easily modify them.
[BLANK_AUDIO]
Yup, that's it.
And then, here are a couple examples.
These are 3D shapes and these are the structure editors.
And then here let me briefly describe the other [UNKNOWN] 2D stroke to 3D shape.
So as I said the basic assumption.
The main idea is to assume constant curvature in 3-D space.
Which means second derivatives, exposition of second derivative of
zed, z positions by y value, is the constant.
Y is a growth direction.
See here again, this is two-dimensional input on X-Y plane.
Y is a growth direction, and x is sideways vectors and
then we compute, we try to compute z values in this way.
So you don't have passed the project stroke onto x y plane and resample.
So we put the sample points here, and
then we suppose that 3D curvature is constant so.
Second derivative of X along Y and second derivative zero Y equal constant.
And we know this volume by this shape.
We also will assume this constant body
by maximum of this volume, we summarized here.
Maximum curvature.
And here.
The curvature in X-Y plane gets smaller here.
But instead we at, assign large value here,
which means large curvature in three directions, and here.
So this is given value, and this is given value, and you get this value.
And after get this values secondary letter Z, just integrate twice,
and then you will get the variable, so that is the algorithm.
So to learn more, the original paper can be
found in SIGGRAPH 2005 titled Floral Diagrams and Inflorescences.
Interacting from our modeling using our botanical structure research.
Now, interactive modeling has a long history of
research, and one famous book is called The
Algorithmic Beauty of Plants, and this one discusses
some really interesting techniques using model based systems.
So here is a, one, example, you draw this kind of synthesis, and you
will get this kind of very complicated
structure, and this is very beautiful mathematical system.
However, it is a little bit unintuitive for our artists to design more of them.
So this, this entry people use this kind of
graphical rule editor to generate a 3D shape like this.
And this, and this paper about the
paper titled, Modeling Methods and User Interface for Creating Plants, was
currently available as a modeling system called XFrog.
This is a very popular tool.
If you are interested in this modeling I suggest you take a look at these systems
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