Minart
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Minart/Tutorial/10. Vector Shapes

10. Vector shapes

Besides surfaces, Minart also allows you to render some basic vector shapes.

Drawing shapes

Dependencies and imports

The relevant methods are in the eu.joaocosta.minart.geometry package

//> using scala "3.3.5"
//> using dep "eu.joaocosta::minart::0.6.3"

import eu.joaocosta.minart.backend.defaults.given
import eu.joaocosta.minart.graphics.*
import eu.joaocosta.minart.geometry.*
import eu.joaocosta.minart.runtime.*

Shapes

Vectorial shapes are represented by the Shape abstraction.

Minart already comes with some basic shapes, such as circle and convex polygons, with helper methods in the Shape companion object.

First, let's create a few shapes with those methods.

import eu.joaocosta.minart.geometry.Point

val triangle = Shape.triangle(Point(-16, 16), Point(0, -16), Point(16, 16))
val square = Shape.rectangle(Point(-16, -16), Point(16, 16))
val octagon = Shape.convexPolygon(
    Point(-8, -16),
    Point(8, -16),
    Point(16, -8),
    Point(16, 8),
    Point(8, 16),
    Point(-8, 16),
    Point(-16, 8),
    Point(-16, -8)
)
val circle = Shape.circle(Point(0, 0), 16)

Faces

Notice that all shapes are defined with points in clockwise fashion.

All shapes have two faces: A front face and a back face.

Depending on the way they are defined (or transformed), different faces might be shown.

Minart allows you to set different colors for each face, and even no color at all! This is helpful if, for some reason, you know you don't want to draw back faces.

Rasterizing

Now we just need to use the rasterizeShape operation, just like we did with blit.

In this example we will also scale our images with time, to show how the color changes when the face flips.

There's also a rasterizeStroke operation to draw lines and a rasterizeContour operation to draw only the shape contours (note that not all shapes support this, some transformations can make the contour computation impossible).

val frontfaceColor = Color(255, 0, 0)
val backfaceColor = Color(0, 255, 0)
val contourColor = Color(255, 255, 255)

def application(t: Double, canvas: Canvas): Unit = {
  val scale = math.sin(t)
  canvas.rasterizeShape(triangle.scale(scale, 1.0), Some(frontfaceColor), Some(backfaceColor))(32, 32)
  canvas.rasterizeShape(square.scale(scale, 1.0), Some(frontfaceColor), Some(backfaceColor))(64, 32)
  canvas.rasterizeShape(octagon.scale(scale, 1.0), Some(frontfaceColor), Some(backfaceColor))(32, 64)
  canvas.rasterizeShape(circle.scale(scale, 1.0), Some(frontfaceColor), Some(backfaceColor))(64, 64)

  canvas.rasterizeContour(triangle.scale(scale, 1.0), contourColor)(32, 32)
  canvas.rasterizeContour(square.scale(scale, 1.0), contourColor)(64, 32)
  canvas.rasterizeContour(octagon.scale(scale, 1.0), contourColor)(32, 64)
  // Can't compute the contour of a circle scaled on only one dimension
  //canvas.rasterizeContour(circle.scale(scale, 1.0), contourColor)(64, 64)
}

Putting it all together

val canvasSettings = Canvas.Settings(width = 128, height = 128, scale = Some(4), clearColor = Color(0, 0, 0))

AppLoop
  .statefulRenderLoop((t: Double) => (canvas: Canvas) => {
      canvas.clear()
      application(t, canvas)
      canvas.redraw()
      t + 0.01
    }
  )
  .configure(canvasSettings, LoopFrequency.hz60, 0)
  .run()
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