FXmap function

[lebulb]

Hello,
is it possible to achieve this (gif), with a single quadrant?
(with function in the pattern offset)

[Cyrille Damez]

Yes. You'll need two functions :

• one in the iterate node to set the number of iterations and save it in a variable
• one in the pattern offset that computes how much to shift each pattern based on the number of iterations and on the float variable $number that gives you the current iteration number.

[lebulb]

Great! it works.
Thank you.

I thought the $number was the iteration number... it's clearer now 


EDIT : Why $number is not a integer variable, if is the current iteration number?

[lebulb]

Hi!
Another question about FXmap.

I try to make a random integer on a iteration but it dont work.
I dont understand, because it work with a simple float number (Float > To Integer)





Also, is it normal that a FXmap node does not switch to 16 bit when the Imput Image 1 is in 16 bit?
Its only with the background?

Thank you in advance.

[lebulb]

Nobody for my random Integer?   

I try to make a complexe Generator Pattern and i need this functionality.
Maybe my method is wrong? I have tried many things.
How to convert a decimal number by an integer otherwise.
But it sounds like a bug. Can you confirm?

[Wes McDermott]

Nobody for my random Integer?   

I try to make a complexe Generator Pattern and i need this functionality.
Maybe my method is wrong? I have tried many things.
How to convert a decimal number by an integer otherwise.
But it sounds like a bug. Can you confirm?

Hi,

I'm sorry, but I'm not sure. I will check with the devs and post back.

Cheers,

Wes

[Vincent Gault]

why don't you plug the integer to the random directly and set the random as output ?

[lebulb]

Because random node doesn't accept integer value. 

Thx Wes!

[Vincent Gault]

and if you multiply your random by 100 before to convert to integer ?

[lebulb]

Thx Vincent
I tried, but I have an inconsistent result as with my other tests.

Logically, it should work with my first method,
I really think there is a problem

EDIT : To be more specific,
I use the node polygon_2 and I would have a random number of sides

[Cyrille Damez]

If you want to draw random integers ranging from 0 to an input integer i (i included) you need to do:

input int -> add 1 -> cast to float ->random->floor->cast to int

If i is a constant (e.g. 100) you can directly plug the constant float 101.0 in the random.
The "floor" may be optional. I don't remember if the cast from float to int rounds to the nearest integer, rounds to zero or truncates the decimals.

Also, is it normal that a FXmap node does not switch to 16 bit when the Imput Image 1 is in 16 bit?

Yes, the primary input is the background.

[lebulb]

Hi Cyrille, once again, thank you very much.
In fact, I made a small mistake in the explanation of my problem.
Indeed, it works on an iteration.

What I was trying to do, its a variable integer, in the sides of polygon2 node,
(which is a integer) and here, it does not work at all.

I had also used the floor node but it change nothing to the result.
I put the .sbs in attachment.

[Cyrille Damez]

It's working as intended.

The Random node outputs a pseudo-random (*) series of number in an iteration (or quadrant hierarchy), but always outputs the same series unless you change its random seed (so that you get the same predictable noises every time you render). If you use Random outside an iteration, it will always give you the same pseudo-random series comprised of only 1 number, which obviously does not look very random.

So in case you really want to create a substance that draws only one polygon with a different number of faces every time you draw it, you need to expose the number of faces as an input to the substance and draw a random number in the application that uses it.

(*) There is no such thing as random in a computer, unless you use custom hardware such as described here :
http://en.wikipedia.org/wiki/Hardware_random_number_generator

[lebulb]

Hi Cyrille, thank a lot again.
Sorry for the delay, i finished the year with a big charette +.+

you're right for the random Integer, my analysis was wrong.
I understand the concept, but by changing the Random Seed, i should have this kind of thing :

but i get that  :

Perhaps then, its the polygon_2 which does not work well.
(or me, which has still not understood something )

I use this function (random Integer [3-7]) in the Sides Instance Parameter (polygon_2):