Dynamic paint - Can you keep object (text) hidden until painted?

Is there any way to make the text “invisble” until it is painted with the particle paint. I want the text to blend in with the wall (be the same material as the wall) and then appear as if it were painted on the wall.

I posted it here because it has to do with dynamic paint, on the other hand it is also a materials question ?


Thank you for any help you can give.

The file is here on dropbox (50.1 Mb)

Picture of render showing wall, text, and paint

I’m at work and don’t have much time at the moment. I will try to download the files and play with them later, but a quick question, are you rendering in Blender internal or Cycles? Either way, couldn’t you have the dynamic paint paint an Alpha mapped transparency texture on the text, making it visible?

What @blazer003 said. Here’s a (theroetical) noodle setup for cycles:

This assumes your text is simply defined by an alpha channel and that dynamic paint also paints to that alpha channel (or just use black and white colour images). Oh and you’ll probably need to add a UV mapping node in there too.

@blazer003 &bigstu80 Thank you for taking the time to look at this issue.

I am using Blender Internal, I am not opposed to using Cycles. Your suggestion of a “Alpha mapped transparency texture” is beyond my current functioning knowledge of blender. However I will research it and see what I can learn about it. My issue with cycles is that I get a lot of noise on most of my renders and I have not learned the techniques for satisfactorily reducing the amount of noise.

I am still quite intimidated by nodes. I see you node setup calls for some image textures - So, am I right in assuming that I will have to use the same image texture for the wall and text? Will your “paint shader” be what the particle system “sprays”?

@bigstu80, Also not clear on what you mean by: “text defined by an alpha channel and that dynamic paint also paints to that alpha channel”.

I hope I am not making things more difficult than they should be, does use black and white color images mean using two b/w images each inverted text & wall respectively so that when placed on top of each other they form an alpha mask? (i.e. solid black)

Off topic question: Do you have your noodle setup’s in groups or are the boxes around the nodes merely frames

Sooooo much to learn :slight_smile:

Thanks again.


@blazer003: Let me explain myself a bit more: I do understand alpha mapping. However, I was unsure how that related to dynamic paint. But after re-reading the "text defined by an alpha channel mapping I think I’m beginning to understand what your saying. Just a matter of figuring out the implementation

OK my Blender Internal node-fu isn’t great but it might give you some ideas:

I’ve forgone the whole ‘alpha channel mapping’ stuff. It works like this:

  • black and white image for text
  • black and white image that is used for dynamic paint
  • brick texture

Text and dynamic paint textures are multiplied together. Think of it like this: a black pixel in the text image multiplied by a black pixel in the dynamic paint image = a black pixel. A white pixel * a white pixel = a white pixel. Most importantly, a black pixel * a white pixel = a black pixel (anything multiplied by zero i.e. black = zero).

So… your text image has white text where the text should be. But while the dynamic paint image is black i.e. not painted, no text will show. As the dynamic paint image gets painted with white, those areas in the text image that match with the paint image will multiply together and come out white! So now it reveals the text where these two images both have white.

But then you have to combine the text with the wall. So I mix the black and white result with blue to make blue paint. Then mix the brick wall image and blue paint together to produce the final material. The noodle that feeds into the materials specularity is kind of saying “wherever the paint text is revealed, make it shiny”, because you know, paint is shiny.

@bigstu80, Excellent! Thank you for the explanation, makes it easier to visualize. I understand exactly what your doing in B.I. Thank you for the help!

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