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How to use roughness, metallic and Bump images

Hi. I need more explanation of how to use the images for roughness, metallic and Bump.

  1. What are the format supported? (PNG, JPG, TARGA…)
  2. How they are generated?
  3. how they are modified when they are loaded?

Anyway, a little more guidance about these settings

Can You help me please?
regards
Jorge.

Roughness texture
In short, roughness texture to roughness scalar setting is, what base color texture is to base color scalar setting.

A roughness texture allows you to vary roughness within one material, so to make a single surface reflect light non-uniformly. For example, you can see the effect of using a roughness texture on the oak part of the table below.


(certain areas are more reflective, and others are less reflective)

A pure black color (0, 0, 0) of the roughness texture corresponds to scalar roughness setting = 0, pure white color (255, 255, 255) corresponds to roughness = 1, with grey colors in between corresponding to roughness values between 0 and 1.

In most cases, a roughness texture is created based on the base color map using such image operations as: desaturate (convert image to greyscale), negate or brightness & contrast (levels).

Below you can compare a cropped and zoomed in base color oak texture used for the table and a corresponding fragment of the roughness texture.
image image

Metallic texture
Metallic texture is used to vary metallicness within one material. For example, you can see the effect of metallic texture on the wallpaper below.

With metallic texture, a pure black color (0, 0, 0) of the texture corresponds to scalar metallic setting = 0, pure white color (255, 255, 255) corresponds to setting to metallic = 1, with grey colors in between corresponding to values between 0 and 1.

Below you can compare the base color wallpaper texture used in the above example and the corresponding metallic & roughness textures (roughness given for completeness):

wallpaper
base color

wallpaper_metal
metallic

wallpaper_rough
roughness

Bump texture
Bump texture is used to model bumps and slits in a surface. For example, you can see the effect of a bump texture on the floor below.

With bump texture, a pure black color (0, 0, 0) corresponds to a deepest slit in the surface, a pure white color (255, 255, 255) corresponds to a highest bump in the surface, medium grey (127, 127, 127) corresponds to regular surface height (neither a slit nor a bump). You can use greyscale values in between to vary slit depths and bumps heights. The overall bump intensiveness for a material is controlled with the Bump scale setting in the editor.

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Thanks @wojtek, I forget to say you.

I tried to use some images in roughness but always got the same error message, is a bug or I’m doing something wrong?

To apply a roughness texture to an object the object is required to have a UV texture mapping. In Shapespark a UV texture mapping comes from the 3D modelling application. If you use SketchUp model as a scene source, the UV texture mapping is imported only if the object has a diffuse texture.

The error states you try to apply a roughness texture to an object without UV texture mapping.

To fix the error you have to modify your source model by adding a diffuse texture to the object. This texture can be even a solid color texture, however its real world dimensions should be the same as the real world dimensions of the roughness texture.

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Thanks @wojtek, At last!