Sialk

Playing it

Layers

Adding, mixing, ordering, removing.

The stack reads bottom-up: the layer at the bottom of the list is drawn first, and everything above it is composited on top.

THE STACK, AS THE LIST SHOWS IT 3 · sparks top 2 · rings 1 · shader bottom drawn first ↑ last GPU one picture layer 1, then 2 on top of it, then 3 on top of that out wall
The layer at the bottom of the list is drawn first. Everything above it composites on top, on the GPU, in one pass, into the picture that goes to the wall.

Adding one

How What
+ add layer At the foot of the stack.
⌘O The same thing from the keyboard.
Drag and drop A folder or a link dropped on the window becomes a layer.
⌘V An address already on the clipboard.

You can browse to a folder, or to the file that starts it. What counts as a valid sketch is in what Sialk plays.

Layers from an address, pasting or dropping a URL, arrive with v1.

Mixing one

Control Where it is Notes
Opacity The amber bar Drag it. A click does nothing on purpose, so selecting a layer can never fade it by accident.
Blend The dropdown normal, add, screen, multiply.
On / off The ON at the top right of the row Keeps the layer and its settings; stops drawing it.
Order Drag the card Or ↑ / ↓, or ⌘↑ / ⌘↓.
Remove Hover the layer's number It becomes ✕. Press it twice, or ⌘⌫.

Removal asks twice by design. One press arms it, the second does it, a single misplaced click during a set should never delete a layer.

The Sialk layer stack: three layer cards numbered 3, 2 and 1 from the top, each with its name, an ON switch, an amber opacity bar reading 1.00, a blend-mode dropdown set to NORMAL, and a frames-painted-over-frames-delivered counter. Below them, the add layer control and the words bottom of stack.
The stack, top to bottom. Layer 1 is at the foot of the list and is drawn first; the counters on the right are frames painted against frames delivered.

Reading the numbers

The two numbers at the bottom right of a layer - 2448/2448 - are frames painted against frames delivered. They should track each other.

If the second number stops moving, that sketch has stopped. The show continues; the compositor keeps drawing the last frame it received from that layer. See when something goes wrong.

A layer with no background is transparent

If your sketch never paints a background, the layer is transparent and whatever is beneath it shows through.

This surprises people, and it is not a bug, it is the same behaviour as a browser source anywhere else. If you want the layer opaque, paint it:

background(0);       // p5

// GLSL: return an alpha of 1.0
fragColor = vec4(colour, 1.0);

Left transparent on purpose, it is one of the most useful things in the stack: a sketch that draws only its shapes will sit over another sketch cleanly with no blend mode needed at all.

Placing a layer

Scale, position and rotation are parameters Sialk gives every layer, whatever the sketch is. They arrive with v1, see parameters.