Time Animation

Learn to create time-based animation effects using the u_time uniform variable and understand the application of sin functions in animation.

Overview

• Use a distance field and a mask to shape the image.

Learning Objectives

• Understand how the u_time uniform variable passes time to the shader.
• Learn to use the time variable to change colors, shapes, or positions to create animations.
• Master using sin() or cos() functions combined with u_time to create smooth periodic animations.
• Be able to implement simple blinking, pulsing, or moving effects.

Prerequisites

• solid-color
• uv-coordinates

Inputs

• float u_time — Time in seconds.
• vec2 u_resolution — Canvas size in pixels.

Key Concepts

• Distance to center builds a distance field.

vec2 p = vUv - 0.5;
float d = length(p);

• Convert distance into a mask.

float mask = 1.0 - smoothstep(r, r + aa, d);

How To Implement (Step-by-step)

• Center coordinates: p = vUv - 0.5.
• Compute distance: d = length(p).
• Build a mask with smoothstep or step.
• Mix foreground/background by the mask.

Self-check

• Does it compile without errors?
• Does the output match the goal?
• Are key values kept in [0,1]?

Common Mistakes

• Clamp t into [0,1] when needed.
• Don’t use raw pixels without normalization.
• Make sure edge0 < edge1 for smoothstep().