Shotcut Motion Masking Effect Using Glaxnimate

“In this tutorial, I will demonstrate how to do the Wipe Mask transition using the new Glaxnimate tool on Shotcut.”

At 0:00 the video is still running the channel intro reel, so this frame shows other effects rather than this one — the technique itself is first visible on screen at 1:10. The plan is stated in the opening line: a shape drawn in Glaxnimate, animated frame by frame, cuts a moving hole in the top clip.

“This tutorial is done on Shotcut version 22.12.21. Please make sure you have at least this version otherwise you may not have the necessary features like Glaxnimate.”

The About Shotcut dialog on screen reads Shotcut version 22.12.21. That is the build every panel, filter name and menu path on this page was read from. Shotcut ships with Glaxnimate from this era and is launched from inside it — on an older build the Mask: Draw (Glaxnimate) filter may simply not be in the list.

“So in this technique what I’m trying to do is as this woman is walking across the screen she then exposes the video underneath it.”

This is the whole idea in one frame. The walker is on the top track; everywhere her body has already passed, the night footage on the track below is showing through. The mask is not a fixed shape sitting in the middle of the frame — it grows and changes with her, which is what makes it motion masking rather than a static vignette.

“So in this technique I’m only going to need two videos. The first one is the walking video and then the second one is the video that gets exposed underneath.”

Two clips in the Playlist and nothing else: Walk.mkv at 00:00:01:20, and Time Square.mp4 at 00:00:08:02. The short one is the clip that gets masked, the long one is what shows through. Note that the reveal clip is the longer of the two — it has to be, because it has to still be there after the walker has crossed.

“So if you go to this icon here and click it, what we’re going to do is we’re going to choose Add Video Track and then we’re going to do it again.”

The Timeline menu button, then Add Video Track, twice. The result is the two empty track heads visible here: V1 created first, then V2 stacked above it. Stacking order is the whole composite — whatever sits on top is what the viewer sees until something removes part of it.

“We’re going to drag the walking video on the top track and then we’re going to drag the Times Square video on the bottom track.”

Walk.mkv goes on V2 and Time Square.mp4 goes on V1. Only the top clip will carry a filter. Because V2 completely covers V1, nothing from the lower track can be seen yet — the mask is the only thing that will ever let it through.

“All I’m going to do is go to the very end of the first video and put my cursor there and then I’m going to click S on the keyboard and then I’m going to delete the overage.”

Park the playhead at the end of the short clip, press S to split the long one at exactly that point, then delete the tail. This is housekeeping rather than technique — but a timeline where both clips end together is far easier to keyframe against, and the extra Time Square.mp4 of reveal footage is doing nothing.

“I’m going to search the top video for the first frame that we’re going to use to edit, which is probably here, is the first time something is exposed in this area here.”

Two more presses of S isolate a middle section of Walk.mkv — from the frame where the walker first starts to clear the edge, to the frame where the screen is completely clear of her. Only that slice gets the mask. Everything before it stays fully covered and everything after it is deleted later, so there is no point keyframing either.

“I’m going to go to filters and then I’m going to look for mask draw Glaxnimate.”

With the split section selected, open Filters and type mask in the search box. Five results come back — 360: Equirectangular Mask, Mask: Apply, Mask: Chroma Key, Mask: Draw (Glaxnimate) and Mask: From File. The one this effect needs is Mask: Draw (Glaxnimate), and it is the only one of the five that can change shape over time.

“The first thing you’re going to need to do is you’re going to need to create a new Glaxnimate file. So I’m just going to call this one New Glax and save.”

Adding the filter does nothing visible — the panel just reads Click New... or Open... to use this filter. Clicking New... opens a Windows save dialog titled New Animation File. Here it is saved into Desktop → SHOTCUT Stuff → Glaxnimate as New Glax, with Save as type left on All Files (*); Glaxnimate writes its own .rawr extension, so the file on disk becomes New Glax.rawr.

“Now Glaxnimate is actually a totally different software that’s integrated into Shotcut. So whenever you want to access Glaxnimate what you need to do is you need to launch Glaxnimate. So it doesn’t exist inside of Shotcut.”

Saving launches a separate program. The title bar reads New Glax.rawr - Glaxnimate and the window has its own menus — Layers, Object, Path, Text, Plugins, Help. The document it hands you is already the right size: the Layers panel lists width 1920 and height 1080, and the clip from the Shotcut timeline is loaded behind the canvas as a reference to trace over. Its own small timeline runs 0 to 33.

“First select this tool over here. And when you select this tool you need to make sure that both the fill and stroke check boxes are checked.”

The third tool down the left-hand toolbar is the bézier pen — the one that draws a shape point by point. Selecting it fills the Tool Options panel with a Create group: radio buttons for Raw Shape, Group and Layer with Layer selected, and checkboxes for Fill and Stroke, both of which must be ticked.

“What you need to do is you need to go to the timeline area here and select this icon here that signifies record. Basically what you’re going to do is you’re going to record the keyframes.”

The last button on the Glaxnimate timeline toolbar, after the first/previous/next/last frame controls, is Record — the tooltip is visible here. This is the step the whole effect depends on. With Record off, reshaping the path just edits one static shape; with it on, every change you make lands as a keyframe on the current frame. From this point the status bar reads Recording Keyframes.

“We’re only going to select the area of the first frame that we want to disappear. So what we want to do is we want to cut that area out so that when we place it on top of the other video it then shows through.”

On frame 0, click point to point around the region that should be transparent — here the strip of pavement the walker has already cleared on the left. The filled white shape appears as Path 1 in the Layers list. White is just the tool’s default fill; what matters to Shotcut is the geometry, not the colour.

“When I advance to the next keyframe what I’m going to need to do is I’m going to need to go to this icon here. And I’m then going to need to modify the previous selection that I just made.”

Advance one frame with the right arrow key, then switch to the second tool down — the node editor. The path’s points appear as small squares that can be dragged to follow the subject. Ben’s point is that you do not redraw the shape each time: you drag the existing points, and Glaxnimate records the difference as the next keyframe. The frame counter at the left of the timeline, reading 1 f here, is the only place that tells you which frame you are editing.

“I’m going to spare you the boring process of me keyframing every single one of these frames by just fast forwarding through this process… So the last thing I need to do is save the file.”

The middle of the job is a fast-forwarded montage: step a frame, drag the points, step again. By the end the shape has grown to cover almost the entire canvas, because by the last frame almost the whole screen should be showing the clip underneath. File then Save, and the status bar confirms File saved. One observed oddity worth flagging: the title bar still reads New Glax.rawr while the document node in the Layers list now reads Glax02 — the file being saved is the one named in the title bar.

“So now that we’re back in Shotcut, the first thing we need to do is we need to make sure that the file we saved on Glaxnimate is updated in Shotcut. So all you need to do is go to this button and click Reload.”

Closing Glaxnimate returns you to Shotcut with the filter panel exactly as you left it — except the label beside New... and Open... now reads New Glax.rawr. Shotcut does not re-read the file on its own, so press Reload. The two applications only talk to each other through that file on disk; nothing is live between them.

“It’s showing the opposite of the mask that I just created. But there’s an easy solution to this. All you need to do is go to this checkbox here and click Invert.”

On the first play the wrong half is transparent: the shape you drew is what stays, and everything else disappears. Ticking Invert flips it, and the drawn shape becomes the hole instead. Operation is left on Overwrite throughout. Expect this — it is not a mistake in the drawing, it is just which side of the shape the filter treats as the mask.

“I just need to go to the very end here, choose this selection here and delete it. So once I play, it then completes the exercise.”

The last section of Walk.mkv — the part after the walker has fully cleared the frame — is deleted, so the composite ends on the reveal clip alone rather than cutting back to a covered frame. This is the finished output: the night footage fully exposed, having been uncovered by a shape that followed a walking figure across the frame.