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SKILL.md
npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill shader-programming
Write game shaders from cross-engine fundamentals — the vertex→fragment pipeline, coordinate spaces, UV math, and common 2D/3D effects (tint, UV scroll, dissolve, outline, fresnel rim, vignette) in GLSL with HLSL equivalents. Use when the user mentions shaders, fragment/pixel shader, vertex shader, UV, GLSL, HLSL, or effects like dissolve, outline, or rim light.
npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill shader-programming
Shaders are small programs that run per vertex and per pixel on the GPU.
The concepts — the pipeline, coordinate spaces, UVs, and how common effects are
built — port across engines; only the language dialect and built-in variable
names change. This skill teaches those portable fundamentals in GLSL with HLSL
equivalents; use godot-shaders (or Unity/Unreal material docs) for the exact
engine syntax and built-ins.
When not to use: for an engine's exact shader language and built-ins, use
godot-shaders (Godot shading language) or the engine's material docs. For full
particle VFX systems, see unreal-niagara. For post-process stacks, defer to
the engine's renderer settings.
0..1 texture coordinates;
offset, scale, or distort them, and animate with a time uniform.mix, step, smoothstep, and
clamp over if where possible; GPUs run pixels in lockstep and dislike
divergent branches.GLSL-style fragment snippets (close to Godot's canvas_item/spatial
shaders and OpenGL). See references/effects.md for the HLSL equivalents and
the full outline/fresnel/vignette shaders.
dot() results drift. normalize() in the fragment stage.step/smoothstep/
mix; reserve if/discard for genuinely cheap early-outs.discard defeats early-Z and can hurt performance on tiled mobile GPUs;
prefer alpha blending where you can.highp vs mediump matters; large UVs or time values
in low precision shimmer. Use adequate precision for coordinates and time.mix↔lerp, fract↔frac, texture()↔.Sample(),
vec2↔float2, column- vs row-major matrices. See the reference mapping.references/effects.md — full outline (2D sprite + 3D), vignette, and color
grading shaders; the GLSL↔HLSL function/type mapping table; per-engine notes
(Godot canvas_item/spatial, Unity ShaderLab/HLSL, Unreal material nodes).godot-shaders — Godot shading language syntax, built-ins, and screen-reading.unreal-niagara — GPU particle VFX (a different shader use).procedural-gen — the noise that drives dissolve and procedural texturing.// Add time * speed to the UV to scroll. fract() wraps it into 0..1 so it tiles.
uniform sampler2D tex;
uniform float time; // seconds, supplied by the engine
uniform vec2 scroll_speed; // UV units per second, e.g. (0.1, 0.0)
in vec2 uv;
out vec4 frag;
void main() {
vec2 scrolled = fract(uv + scroll_speed * time); // HLSL: frac(...)
frag = texture(tex, scrolled);
}
// Drive with a real time uniform, not a per-frame accumulator, so speed is stable.// Hide pixels where noise < threshold; tint a thin band at the boundary.
uniform sampler2D tex;
uniform sampler2D noise_tex; // grayscale noise, 0..1
uniform float amount; // 0 = fully visible, 1 = fully dissolved
uniform float edge = 0.05; // width of the glowing edge band
uniform vec4 edge_color;
in vec2 uv;
out vec4 frag;
void main() {
vec4 c = texture(tex, uv);
float n = texture(noise_tex, uv).r;
if (n < amount) discard; // cut away dissolved pixels
float e = smoothstep(amount, amount + edge, n); // 0 at the edge -> 1 inside
frag = mix(edge_color, c, e); // HLSL: lerp(edge_color, c, e)
}// Rim = 1 where the surface faces away from the camera (silhouette glow).
in vec3 world_normal; // normalized, world space (from the vertex stage)
in vec3 view_dir; // normalized, surface -> camera, world space
uniform float power = 3.0;
uniform vec3 rim_color;
out vec4 frag;
void main() {
float f = pow(1.0 - clamp(dot(world_normal, view_dir), 0.0, 1.0), power);
frag = vec4(rim_color * f, 1.0); // add to lighting; f peaks at the silhouette
}
// Correctness: normal and view_dir MUST be in the same space and normalized.