0:12
And the program we want to address here,
is that it is tedious to illustrate fluid flow.
Suppose you have a engineering system or architecture.
Or organic shapes or a liver system.
There is a lot of fluid systems, and you may want
to describe how the fluid flow in these kind of systems.
And then you want to get these kinds of results.
And it's very tedious to draw them manually.
So, our idea is to use automatic flow simulation
to automatically synthesize this kind of data for illustrations.
So here, the simulation is not used for prediction,
but this is used for a niche [UNKNOWN] illustration.
0:58
So let me show you a video
[BLANK_AUDIO]
So this is basically a drawing system.
You draw something, and the system
continuously runs fluid simulation behind the scenes.
And they add fluid flow visualizations automatically.
So you draw something, a region.
1:24
And then you draw pipes.
And then as soon as you finish drawing
a system, system starts flow simulation behind the scene.
So it visualize a, a detail flow, and also shows the result of fluid mixtures.
[BLANK_AUDIO]
So this tool is very useful for explaining fluid phenomenons.
[BLANK_AUDIO]
2:47
So here this heart has very specific configuration.
And not very ideal.
And here ideally blue blood come from the body, should directly
go to the lung, and then from the lung, fresh blood, red
blood comes into the heart, and then red one should go through the body,
however here blue blood is mixed together with red one.
And then purple one go to the body.
So, doctors will perform a surgical operation to fix this.
However, before they that, they need to explain what
they do to their patients, or their patients' parents.
However, it's very difficult to do that with
standard tools, currently, they use standard pen and ink.
Black and white illustration to describe them,
however, it's very difficult to understand it.
3:40
But preparing this kind of beautiful illustration using computer
system, is too time consuming, and more importantly, this kind
of heart disease has different configuration for each patient,
so it's not possible to prepare a template before hand.
So, this kind of tool can be very useful.
To explain and understand complicated flow phenomenon.
And then let me show you how it works.
So first, the
4:19
So doctor cuts here and then connect them.
So, as soon as the configuration changes,
the fluid simulation changes the flow, prediction.
[BLANK_AUDIO]
So next one is the most important one.
The doctor stops here, cut here, and then connect here.
And therefore, blood suddenly changes.
[BLANK_AUDIO]
And finally, in closing this hole and then
let blood directly go to the body, being red.
[BLANK_AUDIO]
And this kind of technique can be very useful for various
fluid phenomena inside of your body, like blood circulation and others.
[BLANK_AUDIO]
5:25
And also this technique is, can be used for engineering systems.
Like this one.
[BLANK_AUDIO]
And this is another example in [UNKNOWN] so you can see
how cold air and le warm air mix together and flow.
And you can test many different configurations.
[BLANK_AUDIO]
And this tool can be also used for,
for explanation of pollution of rivers, and so.
6:02
And so now let me describe the other region briefly.
So what we use is a hybrid fluid simulation system.
So user draws global network with local regions.
And we apply different simulation [UNKNOWN] for different scale.
Because single scale simulation can be very slow.
6:37
And so, to use a [UNKNOWN] node inflow, and there forms
a global network structure, hydraulics compute it's pipe flow and the
node pressure, and then from this node pipe flow and node pressure, hydrodynamics
computes a detailed, computes detailed flow, inside of this region.
7:00
So this is a little bit in too involved, but let me describe the way.
The first line is hydraulics simulation for a global network.
Here, input is node inflow Qn, so how much flow comes in from the node.
And then what we compute is pipe flow from node inflow.
And hydraulics is a simplified computational method directly computed
from compute from node inflow, and to get a pipe flow.
And after pipe flow, we can compute a pressure, pressure drop at this pipe.
And then from pipe pressure drop, we can
compute the node pressure inside of each node.
And you can get these all information by solving a linear global system once.
It's very fast and it's very efficient.
And after computing pressure node, and [UNKNOWN] pipe flow, we
now switch to our regional [INAUDIBLE] so for each local region.
We compute we divide into a lots of grid cells
like this one, and for each grade cell, we compute pressure
and velocity, and in order the compute individual pressure and velocity, we
use a very standard established fluid equation called Navier-Stokes Equation.
So this one is a little bit complicated, but
essentially this just explains the relationship with fluid velocity
and fluid pressure, you know, if there's a huge
difference in fluid pressure, and it causes velocity, and so.
And this step basically just solved this equation times
step, each time step on this grid cells inside each region, to get an animation.
8:48
So so original paper was published as
sketch based dynamic illus, illustration of fluid systems.
And if you want to learn more about fluid
animation, I recommend you to read some text books.
One example is Fluid Simulation for Computer Graphics by Bridson.
And this work is an example
of illustrative animation for facilitating understanding.
And interesting early dated work
is, MathPad, which takes mathematical [INAUDIBLE]
expression, and they automatically generates
animation, based on the mathematical expression.
9:26
So that's, this is the end of our
second week of this Interactive Computer Graphics course.
We described dia, diagram beautification.
And [INAUDIBLE] shape manipulation, and also
dynamic illustration with a fluid simulation.
Thank you.
Takeo IgarashiProfessor
