## Programming Contest: ConvexifyMe

graphics

### Next

• 1. animating a knee
I need to animate a human knee (write a program for it, not artistically), but where should I begin. What book(s) on the topic shall I read and how should I create an appropriate model(s) for it? Thank you!
• 2. General curve subdivision
Take a b-spline curve C= C_0 and its control polygon L= L_0. Insert a new knot t_1 to obtain L_1 ,... and so on: L_i is obtained from L_{i-1} by inserting a new knot t_i. If the sequence (t_i) is dense in the parametric interval of C, then it is know that the sequence L_i converges uniformly to C (or more precisely L_i can be parametrized in such a way that it does). The same holds true for B\'{e}zier curves (for exaple because they are special case of b-splines). And now my question: Can the same be proved in more general setup? What properties of curve reprezentation are sufficient (or even better necessary and sufficient)? For example, if a certain curve reprezentation satisfies convex hull property (i.e. C(P_0,...,P_n) \subset \conv(P_0,...,P_n) ) and affine invariance (i.e. T(C(P_0,...,P_n)) = C(TP_0,...,TP_n) ) does it satisfy the above? Variance diminishing?...? Thanks in advance, Przemek
• 3. key frame animation algorithms
Hi members, I am trying to write a program to animate a pictures uisng keyframes. Can You tell me any algorithms that I can use or any useful online resource on this. Thanks a lot, Chamal.

### Programming Contest: ConvexifyMe

```Skybuck's ConvexifyMe Programming Contest:

http://www.**--****.com/

Hello everybody,

Skybuck is back with a new programming contest oh yeah ! ;) :)

For this programming contest the mission is as follows:

A bitmap has to be "convexified" which means the following:

Convex polygons have to be made which describe the boundaries of the red
pixels of the bitmap.

The polygons must be convex.

Further hints:

Each pixel of the bitmap can be considered a box.

This means the pixel's coordinate is actually turned into two x coordinates
0 and 1.

The pixel shares these coordinates with it's neighbours.

So a simply polygon for a single pixel would look like:

(0,0) -----------(1,0)

|                  |

(0,1)-------------(1,1)

The order of the points can be clock-wise or counter-clock-wise.

The goal is to keep the number of convex polygons as low as possible.

The goal is also to keep the number of edges as low as possible.

I am not yet sure which goal should get priority. Maybe goal1 automatically
leads to goal2, or perhaps not.

To get this contest started the same bitmap as the "BoxifyMe" contest will
be used:

See website.

The output and thus the entries for this contest should look as follows:

X, Y (starting point)

X, Y

X, Y

X, Y

X, Y (starting point one more time to indicate it's closed.)

X, Y ( starting point of second polygon )

X, Y

X, Y

X, Y ( starting point of second polygon again to indicate it's closed. )

Example:

0,0

1,0

0,1

1,1

0,0

Good luck and may the convex polygons have mercy on your soul ! ;)

Entries can be sent to  XXXX@XXXXX.COM

The best entry will become the King of the Contest.

Will you be sitting in this chair ?

See website ;) :)

This is your chance to become a King ! ;) :) Even if it's only for a few
seconds, minutes or days ! ;) :)

Hurry up and get that code cracking some output ! ;) :)

Entries/solutions will be made publicly available for further study and
analysis to make sure it's valid.

Overlapping convex polygons are allowed. Though non-overlapping polygon
entries are also welcomed.

I will also be entering the contest.

Goodbye, for now,

Skybuck.

```

### Re: Programming Contest: ConvexifyMe

```I think it might be possible to describe a simple "pixel" based polygon and
then later expand it to a boundary polygon, more suited for opengl and
physics based stuff...

So I might consider changing the competition a little bit to make it
possible to simply submit a "pixel based" polygon" instead of a "boundary
based" polygon.

However first I would need to make sure that I have a "pixel" to "boundary"
polygon converter to make sure that this is indeed possible.

So stay tuned for more details coming in the next days/weeks/months.

Christmas and New year is coming up so I understand it might be a busy weak
for some folks out there... with all this family related stuff going on...
so these contests will run for a long time... maybe even forever...

I can understand if people enter later on in january or so ;) :)

If you do want to enter early make sure you state what type the
input/output/entry is either:

1. Boundary based.
2. Pixel based.

Bye,
Skybuck ;) :)

```

### Re: Programming Contest: ConvexifyMe

```Hmmm...

Bitmaps can probably not be converted to convex polygons because as soon as
a pixel is one line lower it becomes concave lol ?! ;) :)

So I am thinking about deleting this contest again...

I will wait one day to see if anybody disgrees and then I will delete it
again ;) :)

Bye,
Skybuck :)

```

### Re: Programming Contest: ConvexifyMe

```Hmmm...

Bitmaps can probably not be converted to convex polygons because as soon as
a pixel is one line lower it becomes concave lol ?! ;) :)

So I am thinking about deleting this contest again...

I will wait one day to see if anybody disgrees and then I will delete it
again ;) :)

Bye,
Skybuck :)

```

```Hi all, does anyone know about some actual graphics programming contests ?

```