From the course: Learning Silhouette

Isolating a foreground with shapes

From the course: Learning Silhouette

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Isolating a foreground with shapes

- [Instructor] We've now reached the topic of chroma key work where you convert a color range to transparent Alpha. And his often involves covering the green of a green screen to transparency. There are other ways to do this though. In fact, silhouette includes a Powermat's node that allows you to use strokes or shapes to define a foreground you want to keep and the background you want to remove, and it does the conversion of the color range to transparency for you. I've had a few nodes to this project to give that a try. Our goal here is to cut out this teapot, change its color and place it back on top of the original footage. I'll connect the footage to the foreground of the Powermat. Again, you can always find out what the inputs are by hovering your mouse over the input bars. Then Powermat to color correct and color correct to the foreground of composite. Composite has a foreground and a background input. I'll branch off the footage and connect it to the background, then composite to output. So we're going to cut out the teapot with Powermat, change its color with color correct, then place it back on top of the footage with composite. You can find Powermat in the silhouette section, color correct in the color section and composites in the composite section. Let's go to Powermat and draw our strokes or shapes. This is somewhat similar to the magnetic freehand tool you have with the rota node. However, we can use any of the tools here to draw your strokes or shapes. We'll start with the teapot, we'll zoom in and grab the X-plane and then draw a close shape that goes near the edge of the teapots that defines where it is. I'm avoiding the background and the actress, a growler frame. And one thing I haven't mentioned yet is you can change the tangent types on the fly. So here I can right mouse button click on this point and change at the corner. Same with this one, except that neater. I'll go through the handle and make a thin shape and close it. I spend a few moments adjusting the shape to make sure I don't get any of the frame I don't want. That's going to be the foreground. Now define in a moment. It's faster to draw your shapes or strokes first, and then assign them. Let's go on to the next shape, which will be a background shape. The next one will define almost the entire background. Once again, the X-plane, I'll start out a frame, tarnish the corners. I'll surround almost everything. The only thing I'm missing is a teapot. And close that. There's one final shape I need here. And that's a small shape to define this whole. X-plane one more time and close it and adjust, if I need to. Now ray two, assign these shapes to the foreground and background. I have to go to my optic list. That was like my first one, you can see it has a type parameter. This is in the object tab. I'll change that to foreground. To make sure I have a clean alpha mat, I'll click on filled. And that tells the node that area is just solid foreground. I'll go to the second one and set that one the background. Once you have a foreground and background define, it starts to alter the alpha. And then my third one, background also. Now remember to click on filled for each of these. You can see that the node is starting to think now, and it's starting to change the alpha. So it should be complete. Let's take a look, alpha channel, and a teapot is removed. And it's found that edge and it's fairly clean. The node itself also has some parameters you can adjust, such as a sensitivity or it tries to attack the foreground colors and the artifact you can raise if the edge is a bit rough. And the accuracy for the overall accuracy of the calculations. There's times you can get better results with either higher or full. Let's go back to RGB, jump to the color correct. And here we can just change the color. You can make it any color you want to. I'll raise the temperature to make it more cyan. Now it looks like the entire frame is blue, but the aplpha's still there. So by the time I get to the composite, it recognizes that and simply places the cutout to blue teapot back on top of the original footage. So here you go. That's one interesting way to isolate a foreground by using color ranges, which are defined by strokes and shapes with the Powermat.

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