you can fly!? Using Particle Brushes with  image composition software
White Edges on Transparent Background

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 Tutorials

 Project Dogwaffle

TheBest3D.com

Many times, PD Particles will be used not by itself, but as a companion tool with another imaging tool. For example, you may be using Adobe Photoshop, or Photoshop Elements, or Paint Shop Pro, the GIMP or ArtWeaver, to name a few popular professional or free image editing softwares.


For example, you may have a simple background image like this blurry blue cloudy thing created in ArtWeaver. -  and it may represent the background layer.



The goal is of course to add some foliage in front of this, painted in PD Particles. For example, using the 'PineBranches' present amongst the particle brush settings, you can draw a few twiggs, save them and add them into a new layer in your image editing tool.

How to select the Style for Transparent background
When you select a preset, in most cases there won't be any alpha channel component to the particles appearing while drawing. Alpha is needed however so that a mask is created in the alpha channel which can be used by other imaging programs as a transparency mask.

Look for the 'Style' paremeter. In this case, the style is 'Line', which means that the particle's paths are used to draw simple lines along them, without changing size (unless the 'shrinking line' style).



Change the Style to one that include Alpha, such as "Line + alpha", or "Shriking Line +" (meaning shrinking line + alpha)


Now, with alpha selected as art of the Style, you'll notice an animated selection mask of marching ants showing along the edges of the painted particles.


Just 3 brush strokes, that's all it takes for this one:


click to enlarge

Save this in a format that includes the alpha channel, so that the transparency mask is saved too. We recommend using the 'Default Targa' format, which is the native, preferred format for Project Dogwaffle.


A close look at the tip of the twiggs shows that the colors are nicely anti-aliased, transitioning from the particle's colors into the background color.


You can erase the content of your selection (through the alpha mask). Right-click on the Erase icon (the big 'X') and select Erase Selected to Black.

Since it's not just resulting in plain white or plain black, but it's showing a gradual trasition between the innermost parts of the twiggs (black) towards the outer parts (white), this indicates that we also have gradual transitions inside the alpha channel.

In other words, some of the light-grey transitions along the edges will likely remain partly visible when placing this image into a layer over another image with darker background.

Note that if you use the free add-on plugin 'CoolTools' for PD Particles, or if you use PD Pro, you can store the image (RGB color channels) and separately also store the alpha channel as a greyscale image .



In PD Pro you can also easily transfer the apha channel to the Swap channel and from there to the main buffer if you with to work on it.

There are also tools to 'tighten' the scope and reach of the twiggs in the alpha channel, such as contrast adjustments, shrink/grow alpha etc... These may come in handy if you want to make adjustments to the alpha values to reduce for example the amount of white bleeding through along the edges.

One easy way to reduce the white bleeding along the edges, is to create the painting against a dark image, such as with black background. Of course, you might argue that then you might see black bleeing against light backgrounds when compositing it, but that is often less perceptible and less disrupting.

Ideally you could use an image as the background that carries the same or at least similar colors as what you'll use when doing the compositing in the final image editor.

But what if you spent a lot of time already painting this, and now you remember and realize that you should have perhaps started with a different background color than white?

Not all is lost: you can erase the white background to another color, such as black. You can erase 'through the alpha mask', i.e. through the selection. The trick is to first invert the alpha selection values, because initially, after painting with particles, it is the inside of the particle (twiggs and branches) which are opaque, i.e. selected. You will want to invert the alpha values, so that it turns it to the outside.

Use the menu:  Alpha > Invert alpha... (shortcut '|') to toggle the alpha to their complementary values. What's selected and fully opaque becomes deselected and fully transparent, and vice-versa.

Then use the right-mouse button to click the ease tool (the 'X' icon). Select 'Clear selected to black', or clear to any other color in the primary or secondary color.

Here you have the background turned to black (or whatever color you erased it to), and gradual grey values courtesy of the alpha values along the edges.


When done, switch the alpha values back to the original values:


Then save the image in a format supporting 32-bit depth, so that the alpha channel is saved too. We recommend the 'Default Targa' format.

In the case of the Default Targa format, you'll be able to choose the desired pixel depth. Choose 32 bit depth.



Into another Image Editor: ArtWeaver

Now you're ready to load the image of the foliage with transparency mask into another image editor application. For example, using ArtWeaver, you can simply use

File > Open

to open a new document from the previously saved Targa image file with alpha channel. Here we see a first image with blueish clouds. The foliage image appears in the second window above it.
 


The pine branches appear perfectly solid with a transparent background.

Select the entire image, using Ctrl-A.

Then copy the image into the Clipboard. (Ctrl-C)






Then click the other image's window.




Use Ctrl-V to paste the image


In this case, the new image is added as a new layer:


At first look, the pine branches may look fine, but if you zoom in you may notice a little bit of white border around the edges. It's difficult to detect for sure in some cases though, especially if the particle trails are of bright color themselves too.


However, it will be easier to see along the particles that are dark.:



Note that it doesn't come to full bright white along the edges, becasue the transarency is quickly fading to fully transparent at the same time as the color would have evolved towards white background color.



You may want to compare the results from different versions of the pine branches, e.g. when they are drawn against a dark background, or blue background. Remember that you can turn any of the loaded image layes invisible to quickly switch between loaded versions.


Here's an example with a version that was rendered against a back background, or rather, where the background was erased to black thereafter.

Note that some of the noise in the high-contrast regions near the top may be accentuated and exaggerated because of the Jpeg compression. But, to some extent it may also be that we overdid the levels of erasing of the background, causing more darkening than needed along and into the edges.


Painting against Similar Background Colors.
One way to reduce the white or dark brder along the edges is to draw the foliage against similar colors or even the image that will ultimately be used in the assembly in the image editor. For example, in this example, we started with the blue sky image in PD Particles. Then we painted with the particles in '+alpha' style, such as Line+alpha. Then we saved the lot as 32-bit Default Targa, including alpha.


click image to enlarge

Now, ArtWeaver is showing the original plain blue background in the lowest layer (Background layer), the prior branches in layer 1 above, but it is invisible, and the newest version in layer 2, with transparent background:

click to enlarge


Let's have a close-up look at the different parts of the overlaying pine needles:

The dark parts: no more white edges.


The upper , bright twiggs look good too.


and here one more with a litle of everything

Here are a few more examples, using the target background image for ArtWeaver as the background in PD Particles:

the starting image, used as background:
(created fully in PD Pro 4.1)
click to enlarge

samples1: (painted in PD Particles, with alpha in particles,
 but disabled alpha for the screen capture)
click to enlarge

sample2:
click to enlarge


And finally, stacking up multiple layers in ArtWeaver:
click to enlarge