About noise texture non randomness

Hi all :slight_smile:

Playing around with noise texture in nodes, i had improper behaviour from what i expected.

As for some other nodes in wich i found bugs by examining them through my oscilloscope the noise texture node has a strange behaviour; though am not sure it is a bug…

When i hear ‘noise’ i understand randomness and unpredictability.

In noise texture nodes, there’s indeed unpredictability ( i didn’t find repetition ) but there are some strange behaviour when you examine the output data.
Lets talk only about the value output ( fac ) with seems to be an unsaturated version of the color value.

1st of all it has to be mentionned that the output value never reaches 1 nor 0 !!!

I noted the limits of the output wich are about 0.25 for low and 0.75 for high. ( yellow marks.

Moreover, you can see with this high density view that there seem to be some ‘steps’ in the signal. this is more obvious when dilating the time base:

i noted the ‘steps’ in yellow.
And as there are those kind of deterministic leves, there are also pattern repetitions like the ones i surrounded in red or green.

What is you opinion about this ? Am i wrong to be surprised of the ‘unexpected’ behaviour of this noise texture ? Or is it simply normal this texture would raise only 3 or 4 peaks in a Fourier transform ?

Finally i simply found the real noise texture wich is called white noise texture.
This one gives proper and expected output: a real random noise generator :smiley:

Thanks for your lit answers :wink:

And happy blending !

Your expectations were wrong, the default noise node is described in the manual as The Noise Texture node evaluates a fractal Perlin noise at the input texture coordinates. while not perhaps directly clear, perlin noise is a type of gradient noise and with true random values only existing at the lattice points the odds of getting a true white or black are low, but not quite zero.


I think it’s been known for a while that the noise texture doesn’t give random result.

I believe the brick texture is better - might be worth repeating your test with that.

Set the brick colours to white and black and the mortar width to zero. Set the brick height and width to the same value, and set the offset to zero.

This will create an array of squares with a ‘random’ grey scale.