2d matrix transformation (with 2d array) [newbie]

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bittt0r

2d matrix transformation (with 2d array) [newbie]

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in Programming Questions • 3 years ago

I'm working with a 2d array of points to draw a 2d "grid" of points, to get something like this:

00000

then I feed the array so i can have some figures inside it, like this

00000

00110

01100

00000

and I'm trying to translate the info of the array so I can move the figure to the left, like this

00000

11000

10001

00000

doing this: (the matrix is 10 x 10 circles, each one size 18)

void moveLeft() {
int trans = 20;
for (int i = 10; i <= 190; i = i+trans) {
for (int j = 10; j <= 190; j = j+trans) {
int cont = i;
if (matrix[i][j] == 1) {
if (i <= 10) {
cont = cont + 200;
}
matrix[cont-trans][j] = 1;
fill(50);
ellipse(i,j,18,18);
matrix[i][j] = 0;
}
}
}
}

the problem is that the first time I apply the function moveLeft() the circles are redrawn in the same location, only the second time it changes position, and the when I apply moveUp() [similar function, but working with j ] the circles move left first and then up... I can't get why!!! Any help?

The other problem is I can't figure out how to move the circles to the other side, I mean Right and Down... it should be easy but I cant find the way.

Thanks a lot

Replies(6)

PhiLho

Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

First, I see a waste: you allocate a large matrix but use only a small part. You shouldn't map the matrix to the pixel 1:1, you should make a matrix like you show, then multiply the indexes by a factor (plus add a margin) to map them to x, y. It would be much easier to understand... Also don't use magic numbers, create constants (defining the size of the matrix), so you can easily change the size of the matrix without changing all the code.

Second, you must not move only the 1, you must move also the zeros... Drop the test, do the move always.
Last, to move in the other direction, you have to do a reverse loop, otherwise you will overwrite the numbers you have to move later.

bittt0r

Re: Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

Yes, I've noticed the waste of bits (200x200 instead of 10x10, too much) but I didn't have a clue on how to fix it, now I'm working on it...

The reverse loop worked perfectly... I imagine that should be a simple one.

I'll upload a revised version.

Thanks a lot for your feedback.

bblochl

Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

Without further analysis of you programming goals and the rest of the code, you have an infinite loop in

for (int i = 10; i <= 190; o = i+trans){}

because i will stay at 10 forever and therefore i<=190 is true for ever. (i will not be changed in the body of the loop as well - BTW, that would be bad stile.) The expression o=i+trans does not alter i. (o seems to be a global variable, declarated outside the loop. I think in java variables will be "defined" instead of "declarated"?) o will always stay on o = i+trans, say 30 forever, as i stays on 10 forever and trans has the value 20, that will not be changed.

Then you set count =i, say 10 and later cont becomes cont=cont+200, say 210, because i<= 10 is always true for the reasons described above. And o will switch between i (=10) and 210 for ever.

The second loop

for (int j = 10; j <= 190; j = j+trans) {}

is an infinite loop as well, for the same reasons described above.

Why ever you set matrix[i][j] = 0; at the end of the code block is absolutely baffling? Really you only set matrix[10][10]=0, because i and j stay on 10 for ever. The role of the matrix is not transparent for me. To move a circle ( -> ellipse(i,j,18,18);) you do not need any matrix as teh example http://www.processing.org/learning/basics/translate.html shows!

Whatever you wanted to reach with your program, you tried to do it with some faulty constructions.At least I cannot understand the program. I do not understand the connection of the problem moving some points in t a matrix, say adding a constant to every element with the circle?

I wonder that you report there will happen something at all. But be sure that this just happens accidentally and not because of that function moveLeft.

bittt0r

Re: Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

Hi, the loop was wrong, I've just fixed it (thanks).

This is a fragment, I want to learn to work with matrixes to store/transform the location info and then translate it into geometry, it gives me a level of abstraction beyond the translate function.

I'll put some more info.

Thanks

bblochl

Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

correction:
Sorry, I made a mistake! Sorry, I smashed my glasses yesterday.

The second loop
for (int j = 10; j <= 190; j = j+trans) {}
will work properly!

May be you wanted i=i+trans in the first loop? The rest of the text has to be adapted to the new situation.

Why you try to count/count to 190 in the loops, I cannot understand and still I did not analyze the complete code and its meaning and goals.

bittt0r

Re: Re: 2d matrix transformation (with 2d array) [newbie]

3 years ago

Thanks,

And yes, the first loop was i=i+trans (I wrote it wrong).

I had 190 counts because the window is 200x200 pix with 10x10 circles, each of 18px.

This is a fragment of the code, I'll put some more info so its easier to understand.

Thanks a lot for the feedback

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