Drift Shader

Introduction

DriftShader is responsible for rendering the background of maps.

• It is inspired by ShaderToy, which uses GLSL as the shading language.
• BG.ShaderToy.glsl is compiled to a shader and used to render the map and minimap background.
• Browse https://www.shadertoy.com/ for documentation and examples.

Entry Function

void mainImage(out vec4 outSRGB, vec2 fragCoord) {
  outSRGB = vec4(0, 1, 0, 1);
}

• You are required to set the output variable outSRGB to color you want the "pixel" to be.
• outSRGB is expected to be in sRGB
  • I would prefer the output to be in linear, but ShaderToy uses sRGB -- and I want to maintain as much similarity as possible.
  • If you want to output in linear, you need to set the option under Background tab in the map editor.
• There are other settings in the Background tab such as rotation, speed, enable dither, etc..

Global Uniform Values

uniform vec3      iResolution;              // resolution (sort-of)
uniform float     iTime;                    // game-time (seconds)
uniform int       iFrame;                   // not supported yet (always 0)
uniform vec3      iChannelResolution[4];    // iChannel# texture resolution
uniform vec4      iMouse;                   // not supported yet (vec4(0,0,0,0))
uniform sampler2D iChannel0;                // can set via Background tab
uniform sampler2D iChannel1;                // can be set via Background tab
uniform sampler2D iChannel2;                // can be set via Background tab
uniform sampler2D iChannel3;                // can be set via Background tab

Color Conversion Functions

float gx_linear_to_srgb(float linear)
float gx_srgb_to_linear(float srgb)
vec3 gx_linear_to_srgb(vec3 linear)
vec4 gx_linear_to_srgb(vec4 linear)
vec3 gx_srgb_to_linear(vec3 srgb)
vec4 gx_srgb_to_linear(vec4 srgb)
vec3 gx_hsv_to_srgb(vec3 hsv);
vec4 gx_hsv_to_srgb(vec4 hsva);
vec3 gx_srgb_to_hsv(vec3 srgb);
vec4 gx_srgb_to_hsv(vec4 srgba);

gx_get_bg_shader_val

float gx_get_bg_shader_val(int index)

• retrieves the shader value at slot index
• the initial shader values can be set under Background -> Shader Values in the map editor
• these values can be changed via .DriftScript using the void gx_set_bg_shader_val(int index, float value) function.

gx_flip_uv

vec2 gx_flip_uv(vec2 uv) {
    uv.y = 1.0 - uv.y;
    return uv;
}

• Helper to convert between ShaderToy (OpenGL) and DriftShader (vulkan) coordinate systems
• (usually you don't need to use this, provided for convenience)

gx_flip_frag_coord

vec2 gx_flip_frag_coord(vec2 fragCoord) {
    fragCoord.y = iResolution.y - uv.y;
    return fragCoord;
}

• Helper to convert between ShaderToy (OpenGL) and DriftShader (vulkan) coordinate systems
• (usually you don't need to use this, provided for convenience)

VSCode Extension

• WebGL GLSL Editor or GLSL Lint vscode extensions (or any, really..)
• There is no DriftShader specific extension yet

Warning!!

There are differences between DriftShader and ShaderToy!!

• ShaderToy / WebGL auto-initializes variables to 0! DriftShader does not!!!
  • If you copy a ShaderToy shader and it is not working (or crashing), VERIFY all variables are manually initialized to 0 !
• ShaderToy (OpenGL) and DriftShader (vulkan) use different coordinate systems!
  • If you copy a ShaderToy shader to DriftShader, it may render upside-down!
  • May need to use gx_flip_uv and gx_flip_frag_coord.
• DriftShader does not support all of ShaderToy inputs and features.