H2D-Introduction.md

Introduction

Before discussing H2D in-depth, let's introduce a few concepts that we will use throughout the documentation:

Pixels

Pixels (represented by hxd.Pixels) are a picture stored in local memory which you can modify and access its individual pixels. In Heaps, before being displayed, pixels needs to be turned into a Texture.

Texture

A Texture (represented by h3d.mat.Texture) whose per-pixel data is located in GPU memory. You can no longer access its pixels or modify it in an efficient way. But it can be used to display 3D models or 2D pictures.

Tile

A Tile (represented by h2d.Tile) is a sub part of a Texture. For instance a 256x256 Texture might contain several graphics, such as the different frames of an animated sprite. A Tile will be a part of this texture, it has a (x,y) position and a (width,height) size in pixels. It can also have a pivot position (dx,dy)._

Tile Pivot

By default a tile pivot is to the upper left corner of the part of the texture it represents. The pivot can be moved by modifying the (dx,dy) values of the Tile. For instance by setting the pivot to (-tile.width,-tile.height), it will now be at the bottom right of the Tile. Changing the pivot affects the way bitmaps are displayed and the way local transformations (such as rotations) are performed.

Object

An Object (represented by h2d.Object) is the base class of all of 2D objects. An object has a position (x,y), a scale (scaleX,scaleY), a rotation. It can contain other objects which will inherit its transformations, creating a scene tree.

Scene

The Scene (represented by h2d.Scene) is a special object which is at the root of the scene tree. In hxd.App it is accessible by using the s2d variable. You will need to add your objects to the scene before they can be displayed. The Scene also handles events such as clicks, touch, and keyboard keys.

Bitmap

A Bitmap (represented by h2d.Bitmap) is a 2D object that allows you to display a unique Tile at the sprite position.

Example

Now that the basic concepts have been introduced, let's write a small Heaps application:

    class Main extends hxd.App {
        var bmp : h2d.Bitmap;
        override function init() {
            // allocate a Texture with red color and creates a 100x100 Tile from it
            var tile = h2d.Tile.fromColor(0xFF0000, 100, 100);
            // create a Bitmap object, which will display the tile
            // and will be added to our 2D scene (s2d)
            bmp = new h2d.Bitmap(tile, s2d);
            // modify the display position of the Bitmap sprite
            bmp.x = s2d.width * 0.5;
            bmp.y = s2d.height * 0.5;
        }
        // on each frame
        override function update(dt:Float) {
            // increment the display bitmap rotation by 0.1 radians
            bmp.rotation += 0.1;
        }
        static function main() {
            new Main();
        }
    }

Changing the tile pivot

We can easily make the Bitmap rotate around its center by changing the tile pivot, by adding the following lines:

    bmp.tile.dx = -50;
    bmp.tile.dy = -50;