rect: Rectangle Rendering Function

Distance Field-Based Rectangular Geometry with Uniform and Non-Uniform Scaling

The rect function renders precise rectangular shapes using signed distance field techniques. It provides both filled and stroked rendering modes with support for independent width/height control and uniform scaling.

Mathematical Foundation

Rectangular distance field computation uses coordinate clamping: $SDF_{rect}(p, size) = |max(|p| - size, 0)|$ where $p$ is the position vector and $size$ defines the rectangle dimensions.

Function Variants

Function	Parameters	Scaling Mode	Rendering Type
rectFill(st, size)	position, 2D size	Non-uniform	Filled rectangle
rectFillUniform(st, size)	position, scalar size	Uniform	Square fill
rectStroke(st, size, width)	position, 2D size, thickness	Non-uniform	Outlined rectangle
rectStrokeUniform(st, size, width)	position, scalar size, thickness	Uniform	Square outline

Scaling Behavior

Two scaling modes provide different geometric control:

• Non-uniform: Independent width/height control via vec2(width, height)
• Uniform: Proportional scaling via single scalar value (creates squares)

Distance Field Properties

The rectangular SDF exhibits these characteristics:

• Interior points: $SDF < 0$ (negative distance)
• Boundary points: $SDF = 0$ (zero distance)
• Exterior points: $SDF > 0$ (positive distance)

ライブエディター

const fragment = () => {
      const filled = rectFill(uv.mul(4).fract(), vec2(0.5))
      const outlined = rectStroke(uv, vec2(0.1), 0.3)
      const combined = filled.add(outlined)
      return vec4(vec3(combined), 1)
}