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enter image description here

I want to paint vertices like the image (It is done in Photoshop). The first row is red with alpha 1 and the 6th row is red with alpha zero. I want to blend from 1 to zero in specific area.

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  • $\begingroup$ Related : blender.stackexchange.com/a/78289/29586 - ‘smooth’ vertex colors over adjacent vertices. $\endgroup$ – Rich Sedman Mar 9 '19 at 9:57
  • $\begingroup$ Thanks for the reply. Unfortunately I don't have that much experience in Blender. Could you tell me how can I use this solution ? Also blender doesn't have this feature itself ? $\endgroup$ – ATHellboy Mar 9 '19 at 10:43
  • $\begingroup$ @RichSedman I opened your example and deleted that sphere and created plane and as you explained I painted those first row vertices and put those vertices in FIXED vertex group and then click run (Also I changed the name in the code to Plane). But all of the vertices change to red. What did I do wrong ? imgur.com/SoXu34P $\endgroup$ – ATHellboy Mar 9 '19 at 11:45
  • $\begingroup$ Sounds like you’re on the right track - The example in my file as it stands runs the ‘spread’ 250 times - so the color will spread over the whole mesh. Find the line that reads ‘for p in range(1,250):’ and change the ‘250’ to ‘6’ - so it only spreads part way - and you should get the effect you’re looking for (you’ll have to reset the vertex colors before re-running). Hope this helps - if not I can add a proper answer later when I get the chance. $\endgroup$ – Rich Sedman Mar 9 '19 at 11:56
  • $\begingroup$ @RichSedman Thank you very much. It works as I want but I want to know if it is possible instead of gray color, using black ? imgur.com/ZPHwEvC $\endgroup$ – ATHellboy Mar 9 '19 at 13:34
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Similar to the answer to Smoothing vertex_colors values this can be achieved by assigning the 'fixed color' vertices to a Vertex Group and using a script to 'smear' the color from those vertices over the rest of the mesh.

You could use the script in the linked answer but for ease of use I have packaged it into an add-on which is avialable for download from Vertex Color Blend Add-on. To install the add-on, simply Download the file and use the User Preferences Add-ons 'Install from file' option and click the checkbox to enable it.

Once enabled you should have a new option in the Paint menu for Blend Vertex Colors

menuoption

Go into Edit mode on your mesh and add a new Vertex Group - name it something like 'FIXEDCOLORS' and assign the vertices you want to have fixed colors to it. Ensure no other vertices are assigned to that group.

Use Vertex Paint to paint those selected vertices the desired colors - it doesn't matter if other vertices are also painted as those will be ignored by the 'blend' process.

Select the Paint/Blend Vertex Colors option and you should get a popup as follows :

popup paramters

Set the Number of steps and initial red, green, blue settings as desired and the Vertex Group to the 'FIXEDCOLORS' vertex group created earlier and click OK to apply.

After a short delay your vertex colors should be updated to blend the 'fixed' colors over the mesh.

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  • $\begingroup$ The download link says "Not Found". $\endgroup$ – ATHellboy Mar 10 '19 at 8:49
  • $\begingroup$ Thank you very much. There is an error and I don't know what I do wrong. imgur.com/a/82x8RyI $\endgroup$ – ATHellboy Mar 10 '19 at 9:21
  • $\begingroup$ What version of Blender is this? I think the more recent versions of Blender have Alpha included in vertex colors (which it why it’s complaining about 3 instead of 4 - red,green,blue,alpha). I’ll make a change. $\endgroup$ – Rich Sedman Mar 10 '19 at 9:25
  • $\begingroup$ It is 2.79 version. $\endgroup$ – ATHellboy Mar 10 '19 at 9:29
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    $\begingroup$ Yup, seems it was vertex group problem but I don't know why because I check it couple of times :D. Thanks. Also that problem which I had is solved by this add-on. $\endgroup$ – ATHellboy Mar 10 '19 at 10:34

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