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Primitives

Primitives are renderable components which give greater (low level) control over the rendering process. Primitives can be used to directly render points, lines, and polygons.

The PrimitiveSystem allows rendering Primitive components.

Setting up the Primitive System

To set up a PrimitiveSystem, you simply need to provide a message bus.

#include "standard/2d/primitive/primitive_system.hpp"
...
new JamJar::Standard::_2D::PrimitiveSystem(messageBus);

Using a Primitive

To use a Primitive it needs to be added to an entity, and it requires a Transform component alongside it to work.

auto triangle = new JamJar::Entity(messageBus);
triangle->Add(new JamJar::Standard::_2D::Transform(JamJar::Vector2D(0, 0), JamJar::Vector2D(30, 30)));
triangle->Add(new JamJar::Standard::_2D::Primitive(
    JamJar::Polygon({0, 0.5, 0.5, -0.5, -0.5, -0.5, 0, 0.5}), JamJar::Material(JamJar::Color(0, 1, 0, 1))));

This will create a simple triangle, defined by the Polygon provided to the Primitive. The visual element of the Primitive is defined by the Material provided, in the example above it is just a green colour applied.

A Primitive can be configured with the following definitions:

  • Polygon - required, the shape of the primitive.
  • Material - required, the visual material to apply to the primitive, e.g. a texture or colour.
  • DrawMode - optional, default is LINE_STRIP (see the available draw modes here).

Peer Dependencies

The PrimitiveSystem will only work in conjunction with a 2D rendering system, such as the WebGL2System for rendering in browser to a HTML5 canvas. The PrimitiveSystem is only a pre-rendering system, it does not actually draw the sprites, instead it prepares the sprites and converts them into a format that a rendering system can parse and use to draw with.