How Do I Make One Shape Reveal Another Using a Mask in a Motion Graphic?

If you have spent any time watching motion graphics, you have seen shape reveals everywhere. A rectangle slides across the screen and text appears behind it. A circle expands from the center and a logo becomes visible underneath. A wipe transition sweeps from one side and a new scene takes over. All of these effects are built around the same core concept: one shape controls the visibility of another.
This technique is one of the most foundational skills in motion design. Once you understand how it works, it opens up an enormous range of creative possibilities, from clean typographic reveals to cinematic transitions to complex layered compositions. This article breaks down how the technique works conceptually, how to achieve it in several tools, and what variations are worth knowing.
What Is a Mask in Motion Design?
A mask is a shape that controls which parts of another element are visible. Think of it like cutting a hole in a piece of paper and placing it over a photograph. Only the portion of the photograph visible through the hole can be seen. Everything outside the hole is hidden.
In motion design, the shape acting as the mask is typically invisible in the final output. It is only the area defined by that shape that determines what is shown or hidden on the layer below (or above, depending on the tool). When you animate the mask, meaning you change its size, position, or shape over time, you create the reveal effect.
The terminology varies between tools. In After Effects, the function is called a mask and sits directly on the layer it affects. In other tools, the same concept may be called a clipping mask, a clipping group, or a track matte. In Premiere Pro, the shape is referred to as a mask applied through the Opacity property. The underlying logic is identical regardless of the name: a shape defines a region of visibility, and animating that shape creates motion.
How to Create a Shape Reveal in FlashFX
FlashFX is a web-based motion design platform that runs entirely in the browser, with no installation required. Its layer system, keyframe animation engine, and shape tools make it well-suited for building shape reveal effects, and the approach is straightforward once you understand how the layer stack and animation work together.
The core technique in FlashFX uses two layers: the element you want to reveal (text, an image, a shape) and a separate masking shape placed on top of it in the layer stack. By animating the masking shape, you control what is exposed below.
Step 1: Set Up Your Layer Stack
Open FlashFX and switch to Design mode, which gives you maximum canvas space for placing and arranging your elements. Use the Text tool (T) to place the element you want to reveal, whether that is a headline, a logo placeholder, or any other graphic. Position it where you want it to appear in the final composition.
Next, draw the shape that will act as your reveal vehicle. For a clean horizontal wipe, use the Rectangle tool (R) to draw a rectangle that fully covers the text or element you want to reveal. This rectangle will be the shape that moves to expose the content beneath it. In the layer stack, make sure the rectangle sits above the text layer.
Step 2: Use the Layer Stack to Control Visibility
FlashFX organizes every element in a z-ordered layer stack. Elements higher in the stack sit visually in front of elements below them. For the reveal technique, the masking rectangle sits on top. By animating its position, you create the illusion that the element beneath is being uncovered.
The key insight is that the rectangle moves off the canvas to reveal the element beneath. At the start of the animation, the rectangle completely overlaps and conceals the text. As the animation plays, the rectangle slides away, either vertically, horizontally, or at an angle, and the text becomes visible in the space the rectangle vacates. By matching the color of the masking rectangle to the background, the effect reads as the text being revealed rather than a shape moving aside.
For a more advanced version, give the masking rectangle the same color as the background and group it with the element it is concealing. Groups in FlashFX can be moved, scaled, and animated as a single unit, which keeps complex reveals organized and manageable.
Step 3: Animate the Reveal on the Timeline
Switch to Animate mode. This expands the timeline and brings the keyframe controls to the foreground. FlashFX uses automatic keyframe creation: when animation mode is active, any property change you make to a selected element automatically places a keyframe at the current playhead position. There is no need to manually add keyframes before editing.
Move the playhead to the start of the timeline. Select the masking rectangle. Confirm its position so it fully covers the element beneath. FlashFX records this as the start keyframe.
Move the playhead to the point in the timeline where you want the reveal to complete. Drag the masking rectangle off the canvas in the direction you want it to exit, either sliding left, right, up, or down. FlashFX automatically creates a second keyframe at this position, and the engine interpolates smoothly between the two states.
Step 4: Apply Easing for a Professional Feel
Raw linear animation between two keyframes produces motion that feels mechanical and robotic. FlashFX provides 16 easing presets and a custom bezier curve editor. For a reveal animation, an ease-out profile, where the motion starts fast and decelerates into its final position, generally reads as the most natural and deliberate. Select the keyframe that ends the motion and apply the Ease Out preset, or open the curve editor and drag the handles to create a custom deceleration profile.
Per-keyframe easing in FlashFX means the entry and exit of any single animated state can have entirely different acceleration profiles. A reveal that eases out as it arrives, and then eases in as the masking shape exits the frame, creates a motion rhythm that feels considered rather than mechanical.
Scale-Based Reveals in FlashFX
The position-wipe approach is not the only method. An equally common reveal technique uses scale. Draw a shape centered over the element you want to reveal. At the start of the animation, set its scale to zero. FlashFX animates scale as an animatable property on the keyframe timeline. At the end point in the timeline, set the scale to 100 percent of its intended size. The shape expands from nothing, and as it reaches its full size, the element beneath becomes fully visible.
This works especially well with circular shapes for iris-style reveals, or with polygons for more geometric, graphic treatments. Because every shape in FlashFX is fully resolution-independent and vector-based, scaling never introduces pixel artifacts, regardless of the canvas size.
Text Reveals in FlashFX
FlashFX includes an advanced text animation system that provides a purpose-built approach to revealing type. Text can be broken into individual characters, words, or lines, and each unit can receive its own keyframe or a stagger delay that offsets when each unit begins animating. This creates cascading text reveals without the need to manually set up dozens of individual mask shapes.
For a slide-up text reveal, the position of the text is animated upward into view, while the containing rectangle (matching the background color) sits on top in the layer stack and acts as the boundary the text slides into. The stagger controls in FlashFX let you offset each character or word by a fixed delay, producing the sequential reveal effect common in title animations and motion graphics headlines.
Combined with the easing system, per-character stagger timing, and FlashFX's gradient and blend mode capabilities on every element, this approach covers a wide range of professional text animation needs without requiring expressions or scripts.
Exporting the Result
Once the reveal animation is complete, FlashFX exports directly from the browser. The export panel supports WebM (VP8 or VP9), MP4 (H.264), animated GIF, PNG image sequences, and single-frame PNG exports with transparency support. Multiple formats can be queued and rendered simultaneously. The rendering engine is deterministic, meaning the export is pixel-identical every time the same project is rendered, so there is no guesswork between preview and final output.
The Core Concept Applies Across Every Tool
The shape-reveals-shape technique is not specific to any single piece of software. It is a fundamental compositing idea that works the same way whether you are in After Effects, Premiere Pro, Apple Motion, or a browser-based tool. Understanding it conceptually means you can translate the approach to whatever tool your workflow requires.
The Two Core Mask Types
Across every major tool, mask shapes fall into two categories: geometric and freeform. Geometric masks (rectangles, ellipses, polygons) are the faster option and cover the majority of common reveal effects. Freeform masks, drawn with a pen or path tool, allow for organic, custom shapes that conform to specific elements in a composition.
For the vast majority of shape reveal work, a rectangle is the right starting point. It is predictable, easy to animate, and produces clean results. Freeform paths are worth learning once the basic wipe approach is mastered, as they enable reveals that follow the outline of a specific shape, a logo path, or an irregular element.
Animating the Mask Path vs. Animating Position
There is an important distinction between animating the shape that acts as a mask by moving its position, and animating the mask path itself by changing its points over time. Moving the position of a mask shape is the simpler and more common approach: the entire shape moves in one direction, sweeping across the layer it affects. Animating the mask path means individual anchor points of the shape change location over time, which allows the reveal boundary to change shape as the animation plays. This is how organic wipe transitions and shape-morphing reveals are built.
For beginners, always start with position animation. It is predictable, produces clean results, and is directly applicable to the majority of reveal effects you will need in production work. Path animation is a more advanced technique with more variables to manage.
The Importance of Easing on Mask Animations
A mask reveal animated with linear interpolation, meaning the shape moves at a constant speed throughout, almost always feels wrong. The natural expectation in motion graphics is for movement to have some acceleration and deceleration, reflecting how objects move in the physical world. Easing presets handle this automatically.
For reveal animations specifically, Ease Out is the most commonly used profile. The mask shape accelerates at the start and decelerates as it completes the reveal, giving the exposed element a sense of arriving and settling. Ease In is used when you want the mask to exit the frame with a sense of building speed. The combination of Ease In on the entry keyframe and Ease Out on the exit keyframe produces the smooth, professional motion feel you see in broadcast graphics and commercial motion design.
How the Technique Works in After Effects
After Effects is the tool most commonly associated with mask-based reveals, so understanding the workflow there is useful context even if you primarily use another application.
In After Effects, a mask is attached directly to the layer it affects. To create a reveal mask, select the layer containing the element you want to reveal, then draw a rectangle or shape over it using the shape tools or the pen tool. The mask, by default in Add mode, makes only the masked area visible. Everything outside the mask is hidden.
To animate the reveal, expand the mask properties in the timeline, locate the Mask Path attribute, and set a keyframe at the start and end of the animation. At the start, position the mask so it hides the element completely (the mask shape is positioned outside the visible area, or collapsed to a zero-size rectangle). At the end, position the mask to reveal the full element. After Effects interpolates the mask path between keyframes.
The shortcut F9 applies Easy Ease to selected keyframes, which adds an Ease In/Out curve automatically. For finer control, the Graph Editor allows precise adjustment of the velocity curve for each keyframe.
Mask modes in After Effects include Add, Subtract, Intersect, and Difference. For a standard reveal, Add is the correct mode. Subtract is used when you need to cut a hole out of an existing mask. Intersect shows only the overlapping region of two masks, which enables more complex composite shapes.
The Mask Feather property softens the edge of the mask, creating a gradient transition between the visible and hidden areas rather than a hard boundary. For spotlight effects and vignettes, feathering is essential. For clean geometric reveals, it is typically left at zero.
The Track Matte Approach
In After Effects and similar compositing tools, there is an alternative to drawing a mask directly on a layer. The Track Matte system uses a separate layer to define the visibility of the layer below it. This is particularly useful when the masking shape needs to be a complex element, such as a logo, a text layer, or a shape with its own animation.
With a Track Matte, the masking shape exists as its own independent layer. The layer below it is set to use that shape as its alpha matte or luma matte. Alpha mattes use the transparency of the matte layer to determine visibility. Luma mattes use the brightness values, so bright areas reveal and dark areas conceal. This opens up a wide range of creative possibilities, including using gradient fills, video footage, or animated patterns as the masking shape.
The practical advantage of the Track Matte approach is that the mask and the masked element are fully independent. The mask can be animated, repositioned, or edited without affecting the layer it is controlling, and vice versa.
Common Shape Reveal Variations Worth Knowing
The Horizontal or Vertical Wipe
The wipe is the most fundamental reveal. A rectangle moves from one side of the element to the other, revealing the content as it passes. The direction (left-to-right, right-to-left, top-to-bottom, bottom-to-top) is a design decision based on what reads most naturally given the composition. Left-to-right is the most common in Western design contexts because it follows reading direction.
The Diagonal Wipe
A variation of the standard wipe, the diagonal reveal adds energy and dynamism to the motion. The masking rectangle is rotated slightly, and its position is animated so the angled edge sweeps across the element. This is a staple of broadcast graphics and sports motion design, where the harder, more aggressive angle suggests speed and impact.
The Iris or Scale Reveal
The scale-based reveal starts with the masking shape at zero size and expands it to full size over the course of the animation. A circle expanding from the center of a frame to reveal content beneath it is a classic iris reveal, borrowed directly from classic cinema. The same technique with a polygon or star shape produces a more graphic, contemporary feel.
The Spotlight or Vignette Reveal
A soft-edged ellipse mask with significant feathering creates a spotlight effect, revealing a central area of the canvas while the edges remain obscured. This is commonly used for focusing attention on a specific element within a complex composition, or for creating a cinematic introduction where a subject appears out of darkness.
The Text Reveal Behind a Shape
One of the most frequently requested motion design effects is text appearing to slide out from behind a shape. The setup involves placing a rectangle over the area where the text will emerge, positioning the text behind the rectangle in the layer stack, and animating the text's position so it slides into the visible region. The rectangle itself does not move. The text moves into view from behind the stationary shape, creating the illusion that the shape is a window or portal the text passes through.
This technique is particularly clean when the moving shape and the text travel in the same direction, creating a synchronized arrival that reinforces the relationship between the elements.
Practical Tips That Apply Regardless of Tool
Match the mask color to the background. When using a shape to conceal content before revealing it, painting that shape the same color as the background makes the effect seamless. The audience sees only the reveal, not the setup mechanics behind it.
Use grouping to keep reveals organized. In any tool that supports grouping or nesting, group the masking shape with the element it is revealing. This allows you to reposition the entire reveal as a unit without breaking the relative alignment between the mask and the content.
Always ease your keyframes. Linear interpolation on reveal animations almost always looks wrong. Apply an ease-out curve to any keyframe where motion comes to rest, and ease-in on any keyframe where motion begins from a stopped position. This is the single biggest quality difference between amateur and professional motion graphics work.
Keep the first reveal simple. A rectangle moving in one axis is the right starting point. Once that feels solid and properly timed, introduce complexity gradually: a slight angle on the mask edge, a second element revealing with a stagger, a feathered edge. Adding complexity to a working foundation is always more reliable than building a complex system from scratch.
Time your reveal to the content, not the other way around. The duration of the reveal should give the viewer just enough time to read or register the content being revealed. A two-word headline might need only 0.3 seconds. A complex graphic with multiple elements might need 0.8 seconds to a full second. Test by watching the export once and noting where your eye goes and how much time you need to read the content.
Use the reveal as a transition, not just an entrance. The same shape-reveal logic that brings an element onto the screen can be reversed to take it off. A rectangle that wiped in from the left can wipe back out to the right on exit. Matching the reveal and exit motions creates a visual coherence that reads as intentional design rather than assembled pieces.
Why This Technique Matters
The shape reveal is one of those foundational motion design skills that appears simple from the outside but rewards deep understanding. Every variation, from the basic wipe to the complex iris with feathered edges, is built on the same underlying principle: a shape defines a region of visibility, and animating that shape creates motion.
Mastering this technique in any tool, whether you start in a browser-based application like FlashFX or work in a professional desktop environment, will immediately raise the quality ceiling of your motion graphics work. It is the difference between static titles and animated reveals, between cut transitions and wipe transitions, between flat compositions and layered, dynamic ones.
Start with a rectangle and a single keyframe animation. Get that right. Then add the easing. Then try a diagonal angle. Then try a text reveal behind a stationary shape. The technique scales exactly as far as your curiosity takes it.