Noise artefacts when lacunarity is near 1 #112661

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opened 2023-09-21 11:59:47 +02:00 by Charlie Jolly · 4 comments

Charlie Jolly commented

2023-09-21 11:59:47 +02:00

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For all noises that have fractal detail and lacunarity set close to 1 this outputs a zoom type effect.

This is caused by the noise origin occurring in the same place.

It is possible to mitigate this by offsetting the fractal layers but fixing this would be a breaking change.

+#define FRACTAL_OFFSET 1259.0
+
 /* The fractal_noise functions are all exactly the same except for the input type. */
 float fractal_noise(
     vec3 p, float octaves, float roughness, float lacunarity, bool normalize)
@@ -78,7 +80,7 @@ float fractal_noise(
   octaves = clamp(octaves, 0.0, 15.0);
   int n = int(octaves);
   for (int i = 0; i <= n; i++) {
-    float t = snoise(fscale * p);
+    float t = snoise(fscale * p + i * FRACTAL_OFFSET);
     sum += t * amp;
     maxamp += amp;
@@ -87,7 +89,7 @@ float fractal_noise(
   }
   float rmd = octaves - floor(octaves);
   if (rmd != 0.0) {
-    float t = snoise(fscale * p);
+    float t = snoise(fscale * p + (n + 1) * FRACTAL_OFFSET);
     float sum2 = sum + t * amp;
     return normalize ? mix(0.5 * sum / maxamp + 0.5, 0.5 * sum2 / (maxamp + amp) + 0.5, rmd) :

For all noises that have fractal detail and lacunarity set close to 1 this outputs a zoom type effect. ![image](/attachments/ff4355c1-4e5b-4ad7-8193-496357390931) This is caused by the noise origin occurring in the same place. It is possible to mitigate this by offsetting the fractal layers but fixing this would be a breaking change. ```Diff +#define FRACTAL_OFFSET 1259.0 + /* The fractal_noise functions are all exactly the same except for the input type. */ float fractal_noise( vec3 p, float octaves, float roughness, float lacunarity, bool normalize) @@ -78,7 +80,7 @@ float fractal_noise( octaves = clamp(octaves, 0.0, 15.0); int n = int(octaves); for (int i = 0; i <= n; i++) { - float t = snoise(fscale * p); + float t = snoise(fscale * p + i * FRACTAL_OFFSET); sum += t * amp; maxamp += amp; @@ -87,7 +89,7 @@ float fractal_noise( } float rmd = octaves - floor(octaves); if (rmd != 0.0) { - float t = snoise(fscale * p); + float t = snoise(fscale * p + (n + 1) * FRACTAL_OFFSET); float sum2 = sum + t * amp; return normalize ? mix(0.5 * sum / maxamp + 0.5, 0.5 * sum2 / (maxamp + amp) + 0.5, rmd) : ```

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Charlie Jolly added the

labels 2023-09-21 11:59:48 +02:00

Iliya Katushenock added the

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labels 2023-09-21 12:14:29 +02:00

Germano Cavalcante commented

2023-09-21 22:05:27 +02:00

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I'm not familiar enough to say for sure that this is a bug.
Lacunarity was implemented in 0702c24a36 by @Hoshinova

@Hoshinova, could you shed some light on this?

I'm not familiar enough to say for sure that this is a bug. Lacunarity was implemented in 0702c24a36 by @Hoshinova @Hoshinova, could you shed some light on this?

Germano Cavalcante added

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labels 2023-09-21 22:05:51 +02:00

Hoshinova commented

2023-09-22 09:27:54 +02:00

Member

Right, these "artifacts" were also mentioned by some artists in https://blenderartists.org/t/thanks-to-your-help-fractal-voronoi-noise-was-added-into-blender/1448508/26?u=hoshinova
Some Textures like for example low Randomness Voronoi depend on having the same origin, so I wouldn't call it a bug.
If at all I'd add a boolean toggle to add or not add an offset. Simply changing it to always adding it would unnecessarily break backwards compatibility.

Right, these "artifacts" were also mentioned by some artists in https://blenderartists.org/t/thanks-to-your-help-fractal-voronoi-noise-was-added-into-blender/1448508/26?u=hoshinova Some Textures like for example low Randomness Voronoi depend on having the same origin, so I wouldn't call it a bug. If at all I'd add a boolean toggle to add or not add an offset. Simply changing it to always adding it would unnecessarily break backwards compatibility.

Charlie Jolly commented

2023-09-22 12:07:35 +02:00

Author

Member

@Hoshinova so it's a kind of feature/bug :)

Maybe something to look at in your musgrave patch?

@Hoshinova so it's a kind of feature/bug :) Maybe something to look at in your musgrave patch?

Germano Cavalcante commented

2023-09-22 14:40:49 +02:00

Member

Thanks for the info @Hoshinova, I'm closing this report then.

(It can be reopened as ToDo or Design if the team agrees).

Thanks for the info @Hoshinova, I'm closing this report then. (It can be reopened as ToDo or Design if the team agrees).

Germano Cavalcante closed this issue

2023-09-22 14:40:52 +02:00

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labels 2023-09-22 14:41:41 +02:00

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