TVpaint Tutorials

At first look, there doesn’t seem to be any way to do alpha channel masking in TVpaint, but there is… it’s just a little different than what you’r used to in other programs.

Let’s start by opening an image that isn’t to hard to mask so were not fighting 2 battles at once. Something like a rock against a blue sky for example.

Now that you have the image opened, make a duplicate of the main layer.

Go to your effects stack and first add the histogram effect. Then add a Black and White converter effect so it’s on top in the effects stack.

The process is now more or less the same as in other programs, except you’r using a standard layer as your alpha channel.

We need to find the channel with the most contrast between the foreground and the background that we want to mask out. Or the other way around, we can allways invert the layer later.

Select the black and white converted effect in the stack. Start by entering 255,0,0 in the r g and b channels respectively. That shows you the red channel alone. Remember we are looking for the channel with the most contrast between the object and the background, so the red channel is not a good candidate if you loaded the suggested rock against a blue sky image. Enter 0,255,0 to view the green channel alone. Any good? If not enter 0,0,255 to check the blue channel. If you use an image with a blue sky against the object you want to mask out this is probably the best candidate.

Now go to the histogram effect below and drag the white and black sliders towards the middle. What you want is to make the sky pure white, and the foreground object pure black. Drag the sliders until you have the best result and hit apply effects to the duplicate layer.

If there’s any areas that are not pure black and white, add a blank layer above and put this layer into burn blending mode. Select a soft round low transparancy pen at around 50% gray (R127,G127,B127) and paint on any dark areas that needs to be black. If there’s any white areas that are not pure white add another layer in dodge blend mode and fix these areas up.

Now you have your alpha mask allmost done. Select the magic wand selection tool and click in the white area so that is selected and hit backspace to get rid of it.

Now all you need to do is select this layer and click the little checkbox to turn it into a stencil. Now this works as a layer mask, you can only paint on any other layer where this layer is black. If you want to reverse this click the reverse stencil checkbox below the checkbox that turns on the stencil for the layer.

The cool thing about working this way with a stencil as your alpha channel is that it can be used for any layer and not just the layer itself.

You can also just use your masked alpha channel layer to paint on directly. Just click on the preserve transparancy button on the TVPaint toolbar and you can only paint on the areas with pixel data. This works great for grabbing a complex form from a reference image and then painting on top of that so you don’t need to worry about perspective.