The Shadow & Lens Blister Effect
Overview
This page features two simulations to explain a counter-intuitive optical phenomenon. Switch between the views using the buttons above.
1. Shadow View (The "Why")
This view explains the physical origin of the effect. It's not caused by a force like magnetism, but by the simple geometry of light from a source that has a physical size (is not a single point). This creates a fuzzy edge on shadows called a penumbra. As the shadow of a nearer object approaches the shadow of a farther object, the farther shadow seems to "grow" or "blister" out because the nearer object progressively blocks the light that forms the farther object's penumbra.
2. Lens View (The "What")
This view shows what the effect looks like from a "front view," as if you were looking through your eyes or a camera lens. It demonstrates the concept of depth of field and out-of-focus blur (bokeh). The "blister" you see is a mirage-like vision of the out-of-focus object, revealed by the in-focus object.
How to Use
- Shadow View: Click and drag the yellow light source and the two blocks. You can also click to select an object and move it with the Arrow Keys or WASD. Press "Play Demo" for an automated tour. Notice how moving objects changes their depth (Y-position) and affects the shadows.
- Lens View: Use the slider to change the camera's focus. This view automatically updates
based on the object positions from the Shadow View.
- When the slider is to the left (Far Focus), the object farthest back is sharp and nearer objects are blurry.
- When the slider is to the right (Near Focus), the nearest object is sharp and farther objects are blurry.
- Objects closer to the light source appear brighter, simulating realistic lighting conditions.