Displacement height and resolution problem

[zbieraj]

First of all, I (we) think that this is a topic which should be explained in more details on the FAQ website of Chaos Group.

So, we have a problem at the office which is understanding displacement height and resolution. We are making now our own library of materials and we hit the wall.

My question is, how come displacement map does not follow the seamless repetition of displacement, reflection, bump maps? How to approach it to get the right result? Another question - how to avoid having such weird artifacts from displacement map in V-Ray for Rhino? Privately, as mainly C4D user, I cannot get why those two problems occur. It is so easy to set in other V-Ray compatible 3D programs but in Rhino it is extremely annoying. And why Chaos Group is keeping to a random value in displacement "Amount" instead of using, for example, centimeters/millimeters? When I was using RDT's Gravel 01 in C4D the result was perfect, exactly as the RDT showed it in their catalog/website.

This is the shader scene that I made:



To better understand the displacement problems which we have, this is the test gravel which I am testing now for the company (from my private collection - Real Displacement Textures - Gravel 01).



The texture is clearly out of scale, so I changed the UVW to be exactly in scale regarding the texture (130cmx130cm - displacement is calculated to be 6cm high). Because the Rhino is what it is, I made extra box mapping on the surface and set the box to be 130x130x130cm.



I set displacement from 1 to around 15 and kept the resolution at 256. This was the result:



I changed the resolution of the displacement to the resolution of the displacement map, so 4096. Result? Still bad.



To be continued below.

[zbieraj]

I did something else - I tested the same texture on a surface of exactly 130x130cm. Now it worked: The only one problem - very annoying geometry artifacts:





Therefore, again, my question is, how come displacement map does not follow the seamless repetition of displacement, reflection, bump maps? How to approach it to get the right result? Another question - how to avoid having such weird artifacts from displacement map in V-Ray for Rhino? Privately, as mainly C4D user, I cannot get why those two problems occur. It is so easy to set in other V-Ray compatible 3D programs but in Rhino it is extremely annoying. And why Chaos Group is keeping to a random value in displacement "Amount" instead of using, for example, centimeters/millimeters? When I was using RDT's Gravel 01 in C4D the result was perfect, exactly as the RDT showed it in their catalog/website.
https://cdna.artstation.com/p/assets...strender-1.jpg

Moreover, I don't quite get how why displacement in Rhino is pushing the geometry in diiferent way than in other programs. High values of the displacement maps are pushed too high up, where the low are pushes way too low. What the heck?

Also, this problem occured many times with many other textures in the office. Therefore, I (we) think that it is important to address those issues.

Sincerely,

Zbieraj

C.F. Møller Architects
Aarhus, Denmark

https://www.cfmoller.com/

[Grigio18]

I'm pretty sure you're doing something wrong ..

First I suggest you to add many more subdivisions to the plane mesh you need to apply the displacement to (select the plane, go to the properties and set a custom mesh under render mesh settings)
for a detail like this you need at least a 5 cm grid ...





Another important thing to try is to set the displacement texture color space to linear and if you have a 16 bit map use that!, 8 bit maps usually don't have enough information to create a good displacement for close ups ...

[zbieraj]

Ok, so changing displacement color space to linear helped maybe a little bit regarding the 130x130cm surface. However, changing subdivisions to 5cm on the big surface settings did not help, as showed below:



By the way, it is really problematic, that for every texture with displacement you need to put a lot of time and efford to get right results. In other 3D software it is usually just drag & drop the texture and you are ready to render (beside eventually doing some small tweaks to get just better, realistic results). I hope that Chaos Group will do something about the whole displacement problem in V-Ray for Rhino.

C.F. Møller Architects
Aarhus, Denmark

https://www.cfmoller.com/

[Grigio18]

can you tell me the name of the pebble textures?
if I have them I will give it a try ..

[zbieraj]

Real Displacement Texture - Gravel 01

C.F. Møller Architects
Aarhus, Denmark

https://www.cfmoller.com/

[Grigio18]

Hey, I think you are doing something wrong... definitely.

Look at my rendering, it's low quality, a little blurred by strong denoising...

[konstantin_chaos]

Hi guys,

There are a couple of things to consider here:

1. There are 2 types of displacement in V-Ray - Normal and 2D Displacement
The base surface topology and subdivisions have an effect only on the Normal displacement.
If you use the 2D displacement the base topology doesn't matter.

2. Using the 2d displacement (if you'll not do GPU rendering) is preferable in most architectural scenarios because the speed and quality you get with it is quite good.
With the 2d displacement I'd recommend you don't tile the texture but rather modify the geometry UVs.
If you follow that rule it's rarely needed to increase the resolution in the displacement options.

3. The texture that is used as displacement is also quite important.
V-Ray supports both 8 and 32 bit textures with negative color values.
Using 8bit textures will require you to set the Shift to the negative halve of the displacement amount value if you need to preserve the original surface level.
The textures will have to be linear if that was the intent of the creator.

4. The displacement amount is measured in scene units.
If the scene is using centimeters for example - displacement amount of 1 will push the white portions in the texture 1cm along the surface normal.
Black areas in the texture will remain unchanged.

As far as your test is concerned:
Can you share the test scene and the texture data so that I can advise on the correct setup?
I found the texture you're using and rendered it with 2d displacement selected and amount of 1cm.
It renders quite OK out of the box.

Regards,
Konstantin

[zbieraj]

Gentlemen,

First of all thank you for your response. Grigio18, you proved that it should work, and I am then doing something absolutely wrong. But I still have no idea what .

konstantin_chaos, I am sharing the scene below:
https://we.tl/t-Efjz4kuCzC

Zbieraj

C.F. Møller Architects
Aarhus, Denmark

https://www.cfmoller.com/

[Grigio18]

Gentlemen,

First of all thank you for your response. Grigio18, you proved that it should work, and I am then doing something absolutely wrong. But I still have no idea what .

konstantin_chaos, I am sharing the scene below:
https://we.tl/t-Efjz4kuCzC

Zbieraj

C.F. Møller Architects
Aarhus, Denmark

https://www.cfmoller.com/

I took a look at the file.

First of all there is an error on the units, you have set millimeters but your gravel plan is only 130 mm, it should be at least 1300 mm (130 cm).

My advice, for the rendering of medium sized architecture, is to always work in cm.

set the normal map texture in linear color space and edit the mode to normal.

set the displacement texture to linear color space and add proper values for the amount and for the shift (30 to 40 mm for the amount and 0 for the shift shoud work.

I would use the 2d displacement mode, it is faster uses a lot less ram , set the texture size option according to the plane size and its size in px in the render.