Weird behaviour of bump

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wasd
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Weird behaviour of bump

Post by wasd » Mon Aug 13, 2018 10:04 am

I seems to me like bump does not work well with Phong (or whatever it is) smoothing.
  • Luxcore bump + smoothing
    bump-test-4.png
  • Cycles (this is how it supposed to look)
    bump-test-5.png
  • Luxcore bump flat
    bump-test-6.png
  • Luxcore smoothing, no bump
    bump-test-7.png
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B.Y.O.B.
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Re: Weird behaviour of bump

Post by B.Y.O.B. » Mon Aug 13, 2018 11:26 am

Please upload the scene (if possible with all textures and HDRI, or link to it).
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wasd
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Re: Weird behaviour of bump

Post by wasd » Mon Aug 13, 2018 12:33 pm

B.Y.O.B. wrote:
Mon Aug 13, 2018 11:26 am
Please upload the scene (if possible with all textures and HDRI, or link to it).
texture: https://cc0textures.com/post/170225601756/fabric-02
hdri: https://hdrihaven.com/hdri/?h=green_point_park

Object on the image is at layer 3. Material is "plane", it has both luxcore and cycles nodes.
Attachments
bump-test.blend
(805.51 KiB) Downloaded 32 times
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wasd
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Re: Weird behaviour of bump

Post by wasd » Wed Aug 15, 2018 4:12 pm

what about bump?
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B.Y.O.B.
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Re: Weird behaviour of bump

Post by B.Y.O.B. » Wed Aug 15, 2018 9:02 pm

Maybe you can describe in more detail what you think is wrong?
Do you mean that the shadowed areas are brighter?

Some observations:
You are using a texture with a very fine pattern.
This produces the moiré effect we see in the foreground and at some distance to the camera, the individual elements of the fabric are so small that they effectively become noise.
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wasd
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Re: Weird behaviour of bump

Post by wasd » Thu Aug 16, 2018 12:15 am

B.Y.O.B. wrote:
Wed Aug 15, 2018 9:02 pm
Maybe you can describe in more detail what you think is wrong?
Do you mean that the shadowed areas are brighter?

Some observations:
You are using a texture with a very fine pattern.
This produces the moiré effect we see in the foreground and at some distance to the camera, the individual elements of the fabric are so small that they effectively become noise.
Of couse it produce moire pattern, but that's wrong pattern.
On the other hand, nevermind. It should be that "terminator problem". If I get it right, luxcore has problem casting correct shadows over smoothed (Phong interpolated?) polygons at terminator.
Bump, solid color:
bump-c-lux-5.png
No bump, color texture:
bump-c-lux-6.png
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FarbigeWelt
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Re: Weird behaviour of bump

Post by FarbigeWelt » Thu Aug 16, 2018 5:58 am

How deep resp. high is your bump? It looks like it throws shadows causing what you think is wrong.
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wasd
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Re: Weird behaviour of bump

Post by wasd » Thu Aug 16, 2018 8:09 pm

FarbigeWelt wrote:
Thu Aug 16, 2018 5:58 am
How deep resp. high is your bump? It looks like it throws shadows causing what you think is wrong.
How what?
If you're asking me about "bump height" – this parameter is so unrelated to anything, I don't want even talk about that. It should either be made meaningful, or thrown out.
In t-shirt picture it's normal map with height 1.0.
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Re: Weird behaviour of bump

Post by B.Y.O.B. » Thu Aug 16, 2018 9:16 pm

wasd wrote:
Thu Aug 16, 2018 12:15 am
On the other hand, nevermind. It should be that "terminator problem". If I get it right, luxcore has problem casting correct shadows over smoothed (Phong interpolated?) polygons at terminator.
In your first post, I don't see any terminator issues at all.
wasd wrote:
Thu Aug 16, 2018 8:09 pm
If you're asking me about "bump height" – this parameter is so unrelated to anything, I don't want even talk about that. It should either be made meaningful, or thrown out.
In t-shirt picture it's normal map with height 1.0.
If you plug any texture apart from the normal map into the bump slot, the grayscale values are interpreted as elevation, where 1.0 (white) is 1 meter and 0.0 (black) is 0 meter (or something like that, maybe the 0 m is gray, not sure about that).
Anyway, it's an absolute value. That's why you usually have to scale it down, you can use a math/multiply node for this or the bump node (they are the same internally).
From the absolute height passed by the bump texture, the shading normal is then computed.

Now, normalmaps are something different, they directly contain the shading normal.
Their height parameter is a relative one, with 1.0 meaning "just use the shading normal as it is in the normal map" and any other value scales the height (0.5 is "make the height appear half as strong as baked into the normal map").
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wasd
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Re: Weird behaviour of bump

Post by wasd » Thu Aug 16, 2018 11:21 pm

B.Y.O.B. wrote:
Thu Aug 16, 2018 9:16 pm
If you plug any texture apart from the normal map into the bump slot, the grayscale values are interpreted as elevation, where 1.0 (white) is 1 meter and 0.0 (black) is 0 meter (or something like that, maybe the 0 m is gray, not sure about that).
If you're not sure, how should I be? :)
B.Y.O.B. wrote:
Thu Aug 16, 2018 9:16 pm
Now, normalmaps are something different, they directly contain the shading normal.
I've already get the idea, that normal map is something usable.

This is cycles image:
bump-test-e-cycles.png
I've just plugged this map:
http://www.bricksntiles.com/textures/ma ... mp-map.jpg

Everything I've got with luxcore bump is either ugly or very ugly, I won't attach the images.
But you may have the scene. HDRI is the same.
bump-test-e.zip
(156.57 KiB) Downloaded 8 times
P.S. About white being 1 meter and grey being zero or something – these are all words, it (maybe) supposed to be like this, but what I see is something else. It'd be great if there was some convincing images. Made to scale.
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