2D Rotation Matrix

Rotate coordinates using a 2D rotation matrix.

Overview

• Follow the steps to complete the exercise.

Learning Objectives

• Build mat2 rotation
• Apply rotation to shapes

Prerequisites

• uv-coordinates
• time-pulse

Inputs

• float u_time — Time in seconds.

Key Concepts

• vUv is normalized UV in [0,1].

vec2 uv = vUv;

• Animate with u_time + sin/cos.

float pulse = sin(u_time) * 0.5 + 0.5;

• Blend values with mix(a, b, t).

vec3 color = mix(colorA, colorB, t);

• Build a soft mask with smoothstep.

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

How To Implement (Step-by-step)

• Start from vUv.
• Build a soft mask with smoothstep().
• Use mix() to blend outputs.
• Animate with u_time (optional).

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.
• Make sure edge0 < edge1 for smoothstep().