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I am new to Blender and texture paint my mesh. I have base color, color details and bump information images mixed in one material on one texture slot. Bump information image has a normal map.

I need to eraser some information from bump image. When I do it with Eraser Alpha erased polygons turn into black. I cannot find any information in the Internet how I can erase only bump info and reveal base color and the details. Could you please help me to understand that? Thank you in advance! Below attached my node editor. enter image description here

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  • $\begingroup$ Are you using eevee? If so, go to the material properties (right side) and scroll down until you see Blend Mode - make sure it is set to something other than Opaque $\endgroup$ Commented Dec 7, 2021 at 16:21
  • $\begingroup$ Yes, I'm using Eevee. My blend mode is Alpha blend $\endgroup$
    – Valeriia
    Commented Dec 7, 2021 at 17:31
  • $\begingroup$ Erase alpha sets the alpha layer to 0 which makes that part of the texture invisible. $\endgroup$ Commented Dec 7, 2021 at 17:34
  • $\begingroup$ But how to make texture from other images (not the one I'm using Erase Alpha on) visible? $\endgroup$
    – Valeriia
    Commented Dec 7, 2021 at 17:41
  • $\begingroup$ i.sstatic.net/bburY.png <= just to clarify, do you want to make the model transparent at the black spot (=look through) or do you want to remove the bump data (=flat appearance)? The alpha slot of the Principled BSDF only affects the Base Color slot and makes the color transparent (you also need to set the Blend Mode to Alpha Hashed in the material settings.) If you want to get rid of the bumpiness then you need to paint the bump image with this grey color: HEX 808080. This is the "flat" value. Color values that are brighter create a bump and darker values create a dent. $\endgroup$
    – Blunder
    Commented Dec 7, 2021 at 18:22

1 Answer 1

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The Erase Alpha brush mode basically paints the alpha channel of an image black. Add Alpha paints it white. Black means the model is transparent at this spot. The image must have an Alpha channel (RGBA).

You can view the alpha channel if you connect it to an Emission node as show in the screenshot below. The Node Wrangler add-on can do this automatically for you with Ctrl+Shift+LMB.

alpha mask

If you set the Blend Mode in the material setting to Alpha Hashed you should see the hole in Material Preview and Eevee render mode. The render engine must be set to Eevee to see the setting.

If the setting is not correct the spot will not be transparent but shown as black.

material preview

With the Add Alpha brush mode you can fill the hole. In in Image Editor on the left you should see the transparency. The image must have an Alpha channel, of course.

add alpha

To remove the bumpiness of a bump map just paint the image with the grey color 808080 (HEX). Make sure the Color Space is set to Non-Color. The image must not be transparent at that spot.

Brighter values up to pure white will create a bump while darker values will create a dent. Use the Mix brush mode.

paint bump

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