Division by 0 and factor slider

cbc_s10_mathematics_and_images

#1

Hi,

I just wanted to know what the node would give if we were to divide a number by zero, I was expecting to get pure white or pure black, and the answer is :


Pure black!
But if you slightly change the value from 0 to like 0.000001 you get pure white. If it is from 0 to -0.000001 you get pure black. So I guess the 0 Value is arbitrary :slight_smile:

I then tried to understand how the factor slider worked, on the blender manual it says:

Factor
Controls the amount of influence the node exerts on the output image.

Not very explicit :sweat_smile:, so I looked what was the output for each 0.1 factor value on several input values. What I get is the factor is a affine function that depends on the mix type.

For example: Let’s call

  • Input value 1 --> x
  • Input Value 2 --> y
  • Factor Value --> F
  • Ouput value --> O

With the divide type we get O = F ( x/y - x ) + x
With the multiply type we get O = F ( x*y - x) + x
With the add type we get O = F ( x+y - x) + x

From this I conjectured that the Output is Factor_Value * (Mix_type - x) + x

For a quick example:
In this configuration


The Output is O = 0.5*( 2 / 5 - 2 ) + 2 = ( 2 / 10 - 1 ) + 2 = 1.20
Hence the pure white :slight_smile:

It seems to work the same with color input, each value of Green Red Blue is processed like an individual value.

I hope this was clear enough, cheers !


#2

Divide by 0 is undefined. Does that mean black is undefined?