Screen Effects

GUO can give the world a different look: cel shading, ink outlines, black and white, sepia, noir, colour grades, a vignette, a glow around lights, an EGA or handheld palette, CRT scanlines, and colour-blind help. Effects apply to the world only, at the art's own pixels, before the window is scaled up. Gumps, the paperdoll and the rest of the interface are never touched.

Classic, the default, is exactly ClassicUO's picture: no effect runs, and the world is drawn the same way it always was. The decision record is ADR-0023.

Choosing a look

• Options > Video > Screen effects..., or Ctrl+Shift+E in game.
• Before you log in: Settings > Screen > Screen effects shows the look that's on (Off for Classic). The arrows step through the looks, and Off goes back to Classic in one tap. Screen effects... there opens the full menu.
• Pick a look. Each pass has a toggle and its own settings. The sliders and choices come from the shader itself, so a new effect brings its own controls.
• Compare with Classic splits the world: Classic to the left of the gold line, the look to the right. Drag the slider to move the line.
• Save as preset keeps what you have under a new name.

The chosen look is remembered on this device.

The same things by typed command (a client command, like ClassicUO's own):

-postfx list          the looks and the shaders there are
-postfx load Noir     switch to a look
-postfx off           back to Classic
-postfx save My Look  save the current look under a name
-postfx split 0.5     compare with Classic (again to turn it off)
-postfx cost          how long the effects took on the GPU last frame
-postfx               open or close the menu

The looks that come with GUO

Cel, Ink Outline, Posterize, Black & White, Sepia, Noir, Warm Grade, Teal & Orange, Faded Film, Moonlight, Vignette, Glow, EGA, Handheld, CRT, Colour Help (protanopia, deuteranopia, tritanopia), and two that react to the game:

• Blood Rush narrows and reddens the view as you lose health.
• Battle Focus turns colder and harder in war mode.

On a desktop GPU each look costs well under a millisecond a frame. The measured costs are in ADR-0023.

Your own looks

Looks are plain text. Put them in the postfx folder of the client's home (beside settings.json); they appear in the menu, and a file changed while you play is picked up within a second.

{
  "name": "Stormy",
  "description": "Cold and dim when it rains.",
  "passes": [
    { "shader": "grade",    "params": { "temperature": -0.3, "saturation": 0.8 } },
    { "shader": "vignette", "params": { "radius": 0.85, "strength": 0.3 } }
  ],
  "bindings": [
    { "pass": 0, "param": "exposure", "from": "weather", "scale": -0.15, "offset": 0.0 }
  ]
}

• A pass is a shader by name (a built-in, or your own .gdshader in the same folder) plus its settings. A setting is a number, true/false, a colour [r, g, b, a] (0..1), or an image path for a texture (a LUT or palette strip beside the preset).
• A binding drives one setting from the game every frame: setting = offset + scale * value, kept within the setting's range. The values are:
  • hp_ratio and hp_missing (health left or lost, 0..1);
  • stamina_ratio and mana_ratio;
  • light_level (0 bright .. 1 dark);
  • war_mode (0 or 1);
  • weather (0 none, 1 rain, 2 storm, 3 snow);
  • time (seconds).
• Nothing carries over from one frame to the next, so no effect can smear or shimmer the art.

Your own shaders

A pass is a Godot canvas_item shader that reads the pass before it and writes its result:

shader_type canvas_item;
render_mode blend_disabled;

uniform sampler2D source : hint_screen_texture, filter_nearest;
uniform float amount : hint_range(0.0, 1.0, 0.01) = 0.5;   // becomes a slider
uniform int style : hint_enum("Soft", "Hard") = 0;          // becomes a dropdown
uniform vec4 tint : source_color = vec4(1.0);               // becomes a colour picker

void fragment() {
	vec4 c = texture(source, SCREEN_UV);
	COLOR = vec4(mix(c.rgb, c.rgb * tint.rgb, amount), c.a);  // keep the alpha
}

Declare uniform sampler2D light_tex : filter_nearest; to read the client's light buffer (where torches, lamps and spells light the world). Keep sampling nearest: UO's art is pixel art, and filtering it blurs it.

Sharing looks

The Asset Store has a postfx kind: a pack of presets, their shaders and any images they use. Installed packs appear in the menu beside the built-in looks, and your own same-named look wins. See ADR-0019 (Amendment 3).