Hi, im trying to create an expression that makes houdini return to a value of 1 when an even number is present. For example, at frame 3 it will give me a value of 0. which expressions should I use to create this kind of effect?

You can use the modulus operator (%):
$F % 2 == 0

Hello, graham!

Can you explain what this expression means or do for shihhao's question? I am reading it as….when current frame # modulus 2 equals to 0, which I don't understand what it would return to tell if it's even number or odd number. Do we need another expression to tell when == 1?

Thanks and sorry for my newbie question…


David

Hi,

Modulus returns the remainder, so the remainder of any even integer divided by 2 is 0. If it's odd, then it would be 1.

Thanks, pusat!

After some thinking, I am not sure of something still so I hope you can help me to get the concept right.

Since the original poster's example was “return to a value of 1 when an even number is present. For example, at frame 3 it will give me a value of 0” so I am confused…

With the example and $F % 2 == 0, I am thinking
at frame 2, the remainder is 0 so the value returns 1
at frame 3, the remainder is 1 so the value returns 0
at frame 4, the remainder is 0 so the value returns 1
at frame 5, the remainder is 1 so the value returns 0
at frame 6, the remainder is 0 so the value returns 1
……….etc. (am I on right direction?)

I assume $F % 2 == 0 is just a part of the whole lengthy expression so there must be somewhere that we need to define to let it return either 0 or 1, right?

Thanks,

Yes, the expression would still be simple. Just add 1 before the modulus operation:

($F + 1) % 2

You can also do it with the ternary operator (if else) but that would be slower since it has to test for the condition every time.