blender/blender

Noise Texture no longer generates random value Once Coordinates beyond 10^5, this limit is higher for other textures #121969

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opened 2024-05-19 11:04:36 +02:00 by Gerstmann Bradley · 4 comments

Gerstmann Bradley commented

2024-05-19 11:04:36 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 531.61

Blender Version
Broken: version: version: 4.1.1, branch: blender-v4.1-release, commit date: 2024-04-15 15:11, hash: e1743a0317bc

Short description of error

dragging the value shown in the red box, and try a different exponent in yellow box to see how color changes from noise.
It's probably a known limitation, but I want to confirm if this is expected.
Other textures are having a much higher limit

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 531.61 **Blender Version** Broken: version: version: 4.1.1, branch: blender-v4.1-release, commit date: 2024-04-15 15:11, hash: `e1743a0317bc` **Short description of error** ![image](/attachments/a0a42579-6120-4b0a-8f19-8936224f2bab) dragging the value shown in the red box, and try a different exponent in yellow box to see how color changes from noise. It's probably a known limitation, but I want to confirm if this is expected. Other textures are having a much higher limit

284 KiB

Coordinate Limit.blend

922 KiB

Gerstmann Bradley added the

labels 2024-05-19 11:04:37 +02:00

Iliya Katushenock added the

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label 2024-05-19 11:58:32 +02:00

Pratik Borhade commented

2024-05-20 07:34:23 +02:00

Member

Hi, can confirm as well though this might be expected. Was looking at the code in node_shader_tex_noise.cc/noise.cc but didn't quite understand it. so forwarding to devs for confirmation :/

@brecht @Hoshinova any idea?

Hi, can confirm as well though this might be expected. Was looking at the code in `node_shader_tex_noise.cc/noise.cc` but didn't quite understand it. so forwarding to devs for confirmation :/ @brecht @Hoshinova any idea?

Pratik Borhade added

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labels 2024-05-20 07:34:48 +02:00

Brecht Van Lommel commented

2024-05-21 11:15:12 +02:00

Owner

It's indeed a known limitation due to numerical precision.

It's indeed a known limitation due to numerical precision.

Brecht Van Lommel closed this issue

2024-05-21 11:15:16 +02:00

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labels 2024-05-21 11:15:17 +02:00

Hoshinova commented

2024-05-21 18:18:50 +02:00

Member

Brecht is right, but I'd like to add some explanations as to why it happens and why it happens much earlier for Perlin noise compared to the other noise textures.

One of the properties of Perlin noise is that it always evaluates to 0.0 when not normalized (or 0.5 when normalized) when the input consists of only whole integers in all vector components.

Blender's Perlin noise implementation uses single precision floats with a machine epsilon of 1.19e-07 meaning that for numbers that are greater than 1/(1.19e-07) = 8.40e6 there mantissa doesn't have any bits left to store a rational part of the number, effectively meaning that any number greater than 8.40e6 is a whole integer as far as Blender is concerned.
Therefore when evaluating Perlin noise for any coordinates greater than that it always result to 0.0 (or 0.5 when normalized).

Actually precision issues are already visible before reaching 8.40e6:

As can be seen the result gets more quantized the greater the input vector becomes.

This happens to the other noise types like e.g. White Noise or Voronoi as well but with the key difference that unlike Perlin noise they don't just always evaluate to 0.0 making the effect less obvious.

Brecht is right, but I'd like to add some explanations as to why it happens and why it happens much earlier for Perlin noise compared to the other noise textures. One of the properties of Perlin noise is that it always evaluates to 0.0 when not normalized (or 0.5 when normalized) when the input consists of only whole integers in all vector components. Blender's Perlin noise implementation uses single precision `float`s with a machine epsilon of 1.19e-07 meaning that for numbers that are greater than 1/(1.19e-07) = 8.40e6 there mantissa doesn't have any bits left to store a rational part of the number, effectively meaning that any number greater than 8.40e6 is a whole integer as far as Blender is concerned. Therefore when evaluating Perlin noise for any coordinates greater than that it always result to 0.0 (or 0.5 when normalized). Actually precision issues are already visible before reaching 8.40e6: ![Screenshot 2024-05-21 175612.png](/attachments/2f00ec53-a558-4f2d-9a3f-b15f3944234d) As can be seen the result gets more quantized the greater the input vector becomes. This happens to the other noise types like e.g. White Noise or Voronoi as well but with the key difference that unlike Perlin noise they don't just always evaluate to 0.0 making the effect less obvious.

Screenshot 2024-05-21 175612.png

272 KiB

Gerstmann Bradley commented

2024-05-21 19:18:20 +02:00

Author

Thanks! this is really the explanation I was looking for!

Thanks! this is really the explanation I was looking for!

Hoshinova referenced a pull request that will close this issue

2024-05-22 19:58:47 +02:00

Fix #121969: Noise Texture Always Outputs 0.0 Once Coordinates Beyond 8.40*10^6 #122112

Brecht Van Lommel referenced this issue from a commit

2024-05-27 12:48:26 +02:00

Fix #121969: Noise texture outputs 0 with coordinates beyond 8.40*10^6

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