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I am currently learning how to use blender as a tool to clean up and edit 3D scans. I am currently working on really large scans which were split in multiple chunks. Some of the chunks differs slightly in vertex color balance and brightness from each other. To be able to make a complete mesh from the chunks I would like to know if there is a way to adjust parameters such as color tone and brightness and contrast on the separate chunks?

I know that in the "Paint Vertex" menu toolbars there are tools like this (brightness/contrast), but I haven't been able to figure out if and how they can be applied to a complete chunk. I don't even know if the Vertex paint are the right tool for this since it only colors the areas visible in the viewport when I need to make changes that will apply to the whole chunk at once?

Thanks for any helps and have a great day!

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  • $\begingroup$ It's difficult to guess without seeing a sample or knowing more about the workflow (how do you import? Addon that drives the scanner? .obj? .ply?) but you probably need to modify the texture applied to the mesh. This can be done either with nodes (if you are using Cycles) or by just opening the texture in an external program and adjusting exposure. The latter would be faster as many image editing programs (e.g. darktable) have a function to normalize exposures of stacks of images (for timelapses for example) $\endgroup$
    – qwazix
    Commented Jan 3, 2017 at 12:11
  • $\begingroup$ Just out of curiosity - which software are you using for the 3D scans? $\endgroup$
    – piegames
    Commented Jan 3, 2017 at 18:59
  • $\begingroup$ Piegames - Agisoft Photoscan $\endgroup$ Commented Jan 3, 2017 at 19:34

2 Answers 2

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The file used in this question is of Stanford PLY format, vertex colors, no textures.

When the mesh is selected, changes in brightness etc. that applies to the whole mesh is found under:

"Vertex Paint" - "Paint" - "brightness/contrast"-"Hue Saturation level", "Levels" "and "Invert"

The screenshot below demonstrates the solution using the "brightness/contrast" parameters solution

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Now that I think about it I will wager a response with the data you gave.

I suppose that you have a textured object in front of you, like this

Starting point

  1. Save your .blend file to a new folder
  2. Go to File > 'External Data>Unpack All Into Files`

Unpack

  1. Choose write to current folder.
  2. You should then find the textures in the folder your blend file is in.

nautilus

If you find nothing, that means that the textures are already in files and not packed in the blend. A quick but dirty way to get them is this:

  • Go back to File > External Data and click Pack All Into .blend
  • File > External Data and uncheck Automatically Pack Into .blend
  • Continue from step 2 above

So now you have the images at hand. Open them in Gimp, adjust the brightness/contrast with the tool of your preference (I usually use Colors > Levels) and save the file in-place. (File > Overwrite)

(I used colorize here for exaggerated effect because the change in exposure is barely visible in this model)

gimp

Then reload blender by switching to rendered shading mode and back, or using File>Revert (remember to save first)

Shading modes

bucket-colorized

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