Where the bump gets strange

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mischterlampe
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Where the bump gets strange

Post by mischterlampe » Mon Nov 16, 2020 8:35 pm

Hi,

I tried to reacreate a bump, which was done in cycles. I needed a procedural noise, which is very small. I tried it with lux and it looked very strange. I invested some hours and that is the excerpt of it.

I used a procedural dot-texture. With normal scaling everything looks like it should.
Black shadow on the right, light on the left. Reminds me of the Playstation 1.
bump_large_scale.PNG
But when I make the dots smaller by increasing the uv scale, the result of the bump looks strange.
bump_small_scale.PNG
Here is a zoom of it
bump_small_scale_zoom.PNG
This happens to triplanar mapped noise, too.
I think this behavior is the reason why I dont get my desired small bump, right? Is this a bug?

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Sharlybg
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Re: Where the bump gets strange

Post by Sharlybg » Mon Nov 16, 2020 9:52 pm

It simply that the bump value a way too high. Currently it is 10cm aka 0.1. Somthing arround 0.001 to 0.01 should work.
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mischterlampe
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Re: Where the bump gets strange

Post by mischterlampe » Mon Nov 16, 2020 11:05 pm

Ok, lets take the real world example.

This is what cycles looks. The red cube's width is 10cm
cycles_10cm.PNG
If I try to achieve this result with lux, the result looks like this. It looks weired at the bottom of the image.
lux_10cm.PNG
Here is the shader tree, where you can see that the bump value is 0,0001
lux_10cm_shader.PNG
The map before the bump node looks like this
lux_10cm_bumpinput.PNG
If I decrease the scale to 1000, the result looks like this, which is somehow more realistic, but not the goal
lux_10cm_1000scale.PNG
For me, it feels like that the bump gets broken, when the scale is too high. But if that is normal, how can I achieve the result of cycles?

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B.Y.O.B.
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Re: Where the bump gets strange

Post by B.Y.O.B. » Mon Nov 16, 2020 11:37 pm

Is the object scaled?
Can you try to compare Cycles and Lux with exactly the same texture used as bump map (an image texture), to minimize other factors?

mischterlampe
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Re: Where the bump gets strange

Post by mischterlampe » Tue Nov 17, 2020 7:31 pm

No, the object is not scaled.
Here is a video where I added a sphere.
I baked the bump map from the original shader to a 16k tif and applied it to the cycles and luxcore shader to drive the bump. In cycles everything behaves like expected. The baked map and the procedural map do a good bump.
If I take the baked map into the lux shader, it results in a good bump, too. But if i try to drive the bump by a procedural map, the bump doesn't appear. I tried to get the same greyscale "image" out of the baked and procedural map, but the bump results are very different. There are different strength in the bump-node. If I would use the strength of the baked-map node tree on the procedural-map tree I wouldn't see any effect at all.
https://streamable.com/bqg6cv

I'm curious about your answear.

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B.Y.O.B.
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Re: Where the bump gets strange

Post by B.Y.O.B. » Tue Nov 17, 2020 7:51 pm

mischterlampe wrote:
Tue Nov 17, 2020 7:31 pm
If I take the baked map into the lux shader, it results in a good bump, too. But if i try to drive the bump by a procedural map, the bump doesn't appear.
Then I guess the problem is somehow caused by the procedural texture you use in LuxCore.
In the screenshot above you used fBM. Are you aware that this texture produces values in the range from -1 to 1? The negative values might be the cause of the problem, although I'm not sure about that. You could try to remap the values like so:
Attachments
Capture.PNG

mischterlampe
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Re: Where the bump gets strange

Post by mischterlampe » Tue Nov 17, 2020 8:28 pm

Yes, I know that the fBM isnt the best thing to test out. This is why I took the blender cloud node in my latest example. Can you produce a small high frequent noise procedurally for the bump that looks like bump, even when you are 10cm away with the camera? I would happy to see how.

mischterlampe
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Re: Where the bump gets strange

Post by mischterlampe » Wed Nov 18, 2020 11:12 pm

B.Y.O.B. wrote:
Mon Nov 16, 2020 11:37 pm
Is the object scaled?
Can you try to compare Cycles and Lux with exactly the same texture used as bump map (an image texture), to minimize other factors?
I think I figured out something out.
How is process of using a procedural map when rendering? Is it baked to an image? If yes, is there a hard resultion limit?

For my feelings, the "procedural bump" looks okay as long as I have a resolution relation of 1to1. This means, if a virtual 2cm by 2cm cube is 2cm on the monitor, the bump looks ok. If I "zoom" in and the cube gets bigger on the screen, the procedural bump doesnt work anymore. Is it possible, that the procedural map is baked with 72dpi?
My problem now is, that we work in print (300dpi) and we need renderings up to 45 Megapixels.

Here are the image, which led mit to this conclusion.
16k map 2cm cube is 2cm on the screen
16kbump_1to1.PNG
procedural
procedural_1to1.PNG
cycles 16k map
15kbump_1to1_cycles.PNG
Now the close ups.
16k map close up where the 2cm cube is bigger than 2cm on the screen
16kbump_close.PNG
procedural
procedural_close.PNG
cycles 16kmap
16kbump_close_cycles.PNG

Is it possible to change the resolution of the procedural map?

mischterlampe
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Re: Where the bump gets strange

Post by mischterlampe » Thu Nov 19, 2020 9:48 am

I get the same result of the procedural map, that flat look, when I take the 16k map and plug it into the triplanar bump node. What happens there?

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Dade
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Re: Where the bump gets strange

Post by Dade » Thu Nov 19, 2020 9:57 am

Can you post a test scene with something like a cube or a sphere and the same material ?
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