Sprites

Of course, any game needs some graphics, right? In Kwyll there are two main places you can draw pixel graphics, Sprites, and Tiles. A Sprite in Kwyll is a rectangular grid of pixels, Sprites can be various sizes, always in increments of 8 pixels in both axes. So, for example, 8x8, 16x16, 8x16, etc. An arbitrary limit is placed on the maximum size of 32 in either axis just to keep things within reason for the target platforms to maintain performance and limit memory use.

It is important to know that a Sprite doesn't actually 'do' anything in Kwyll, it's just an image, it has no position, it isn't by default drawn to the screen anywhere, in order to get a Sprite onto the screen, it must be used by an Object.

Draw Modes

When assigned to an Object, the object can choose which mode to use to draw the Sprite to the screen, which is best depends on the particular use case in your game. The optons are:

LOAD

The sprite is just placed into each 8x8 cell that it touches, completely overwriting anything that might already be there in the Tilemap or any other Objects. This is normally only used if you know there will be no background where the object is used. This is the fastes sprite rendering mode.

OR/XOR

These two modes combine the pixels of the Sprite with those in the background using bitwise OR and XOR operations. The result is that the background isn't completely wiped out in 8x8 blocks like LOAD mode, but depending on the nature of the Sprite and the tiled background, can result in objects becoming difficult to see.

MASK

This requires that a Sprite is defined with a "Mask" layer, see the Sprite Editor for details of creating mask layers. This mode clears a part of the background in a user defined shape before drawing the sprite pixels into that space. It is the most effective draw mode, resulting in well defined pixels that can be easily distinguished from the background, but is the most costly in terms of both memory use, requiring additional data for each Sprite, and in terms of performance.

Planes

When a Sprite is drawn to the screen it is possible that there will be other sprites in the same place on the screen, so there has to be a way to decide which one is drawn first. This is the role of planes. Think of planes as "layers", with the smallest number being closest to the screen, and increasing numbers going further away. So an Object that has its plane set to 1, will have its sprites drawn over the top of another Object that has its plane set to 2, which in turn will drawn over another Object that has its plane set to 5. This feature may be platform specific, check the details for your platform for details.