I am trying to create an effect where the color (green) spreads from the center and then regresses with a certain path. The only way I have been able to do this so far has been through the dynamic paint function and through using a secondary object as the brush to control where the color is added to the primary object.

In the file found here I have a rounded object which is being painted by an expanding cuboid mesh. The difficulty I am having is with the erase function. Though I have selected "erase paint" with the two lateral rectangles, neither of them is erasing the paint when I examine the bake image result. Their paths are correctly animated towards the center. The only thing that I have found that actually succeeds in erasing the painted color has been to duplicate the original brush, make it 30X its original size and select the "erase paint" option.

Using this method, however does not afford enough control in where the color moves. Color animation does not seem like it should be quite this complicated and I would very greatly appreciate any help you can offer with dynamic paint or suggestions for other ways of achieving the effect located in this video (with the expanding yellow circles). Thank you all, again, I greatly appreciate your help! In essence, I am trying to animate the process of taking a piece of paper, drawing graphite along the surface in a smooth fashion, and then erasing bits of the graphite to reveal the paper below.

I am new to the software and am trying to help my professors make some videos for my medical school classes.

The central cube is the brush as my goal is to have straight edges to the color animation. enter image description here This is the render demonstrating the green color being added. enter image description here By expanding the central cube, the color has been expanded to the entire surface. enter image description here The outer rectangles are then moved in with the intent of removing the color from the outer edges. This is intended to give the effect of the color being removed in the opposite pattern as it was deposited. enter image description here Further central movement is intended to remove the color from the lateral edges proceeding into the center. enter image description here After the bake sequence is complete and the product is rendered, the color is not being removed by the "erase paint" function. The node I used is also demonstrated; it is a image enter image description here

  • $\begingroup$ Please show some of you work in Blender Screen captures. A file reference or a video reference is not replacement for showing your work in the question. Please show your work in the question itself in all future questions. File and Video links in addition are welcome. A screen capture from the video is welcome in the question assuming its fair use and credited. $\endgroup$ Dec 5, 2018 at 3:06
  • $\begingroup$ In the file linked your camera seems to be directed at empty space. $\endgroup$ Dec 5, 2018 at 3:22
  • $\begingroup$ My sincerest apologies for not including the screenshots in the original post. I have updated accordingly and will be sure to continue to insert screenshots in any future posts I make. Thank you for taking the time to assist me! $\endgroup$
    – Mathias
    Dec 5, 2018 at 4:54
  • $\begingroup$ I am trying to understand have a straight line edge of color and what you call a blob. Blob tends to mean to me a curved edge. My goal is to understand you goal. $\endgroup$ Dec 5, 2018 at 6:05
  • $\begingroup$ Fine I see you changed your question specification to a straight edge. $\endgroup$ Dec 5, 2018 at 6:09

1 Answer 1


First Suggestions.

enter image description here

Select for Brushes, for data value Paint Source

Mesh Volume + Proximity

as indicated by the Yellow Arrow. Image Above.

enter image description here

For the Canvas change Resolution to 128 for a higher resolution image and smoother transtions

See Yellow Arrow Image above.

I am not claiming this is the minimal set of changes. You can test the two changes.

This is an improvement. There may be other lesser problems.


  • To have a circular or blob spread, create a sphere or similar blob and use it as your paint brush. Your current box paintbrush is not going to fulfill your goals. A sphere is a standard object and can be further shaped with proportional edit tool which can be searched here at BSE or the general internet. This low cost improvement can be started by you immediately.

  • Experiment with the Dry and Dissolve features of Dynamic Paint.

Other suggestions may come later. My time currently at BSE is expiring.

  • $\begingroup$ Thank you for your suggestion! I will try using a sphere and see if that alters the function with the ability to erase. I chose a square originally because I would like to sharp and straight edges in this particular video (but I can straighten the edges of a sphere and will see if the sphere mesh works better). I have tried varying the dissolve feature, and will continue to do so as an attempt at a work-around. Thank you for any additional suggestions you may have. $\endgroup$
    – Mathias
    Dec 5, 2018 at 4:59
  • $\begingroup$ The only reason I sugested a sphere is to remove the straight edge. The video you suggested to be viewed does not appear to have straight edge. $\endgroup$ Dec 5, 2018 at 6:07

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