UV Scrolling

UV scrolling is the simple act of offsetting the uv by an animated value. It is one of the most fundamental techniques in VFX, appearing in almost every type of effect.

Precision

time can often be very large, which can cause precision issues. When using a seamless texture or othewrise repeating pattern, it is therefor best to use the fractal of direction * time.

vec2 Scroll(vec2 uv, vec2 direction, float time)
{
    return uv += direction * time;
}

[{"code":{"demo":"vec3(noise)","uv":"st = Scroll(st, direction, u_time);"},"label":"Noise","params":[],"template":"#version 300 es\nprecision mediump float;\n\nuniform vec2 u_resolution;\nuniform vec2 u_mouse;\nuniform float u_time;\n\nout vec4 outColor;\n\n\n// Unit-length gradient from lattice point (8 directions).\nvec2 grad2(vec2 p) {\n    float h = fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453123);\n    float a = floor(h * 8.0) * 0.7853981633974483; // k * π/4\n    return vec2(cos(a), sin(a));\n}\n\n// Unit-length gradient from lattice point.\nvec3 grad3(vec3 p) {\n    p = vec3(dot(p, vec3(127.1, 311.7, 74.7)),\n             dot(p, vec3(269.5, 183.3, 246.1)),\n             dot(p, vec3(113.5, 271.9, 124.6)));\n    vec3 g = -1.0 + 2.0 * fract(sin(p) * 43758.5453123);\n    return g * inversesqrt(max(dot(g, g), 1e-6));\n}\n\nfloat noise2(vec2 p) {\n    vec2 i = floor(p);\n    vec2 f = fract(p);\n\n    // Quintic fade (Perlin's improved interpolation)\n    vec2 u = f * f * f * (f * (f * 6.0 - 15.0) + 10.0);\n\n    float n00 = dot(grad2(i + vec2(0.0, 0.0)), f - vec2(0.0, 0.0));\n    float n10 = dot(grad2(i + vec2(1.0, 0.0)), f - vec2(1.0, 0.0));\n    float n01 = dot(grad2(i + vec2(0.0, 1.0)), f - vec2(0.0, 1.0));\n    float n11 = dot(grad2(i + vec2(1.0, 1.0)), f - vec2(1.0, 1.0));\n\n    float n = mix(mix(n00, n10, u.x),\n                  mix(n01, n11, u.x), u.y);\n\n    // Unit gradients ⇒ |n| ≤ √2/2. Scale to [-1, 1]; clamp covers FP error only.\n    return clamp(n * 1.41421356237, -1.0, 1.0);\n}\n\nfloat noise(vec3 p) {\n    vec3 i = floor(p);\n    vec3 f = fract(p);\n\n    // Quintic fade (Perlin's improved interpolation)\n    vec3 u = f * f * f * (f * (f * 6.0 - 15.0) + 10.0);\n\n    float n000 = dot(grad3(i + vec3(0.0, 0.0, 0.0)), f - vec3(0.0, 0.0, 0.0));\n    float n100 = dot(grad3(i + vec3(1.0, 0.0, 0.0)), f - vec3(1.0, 0.0, 0.0));\n    float n010 = dot(grad3(i + vec3(0.0, 1.0, 0.0)), f - vec3(0.0, 1.0, 0.0));\n    float n110 = dot(grad3(i + vec3(1.0, 1.0, 0.0)), f - vec3(1.0, 1.0, 0.0));\n    float n001 = dot(grad3(i + vec3(0.0, 0.0, 1.0)), f - vec3(0.0, 0.0, 1.0));\n    float n101 = dot(grad3(i + vec3(1.0, 0.0, 1.0)), f - vec3(1.0, 0.0, 1.0));\n    float n011 = dot(grad3(i + vec3(0.0, 1.0, 1.0)), f - vec3(0.0, 1.0, 1.0));\n    float n111 = dot(grad3(i + vec3(1.0, 1.0, 1.0)), f - vec3(1.0, 1.0, 1.0));\n\n    float n = mix(\n        mix(mix(n000, n100, u.x), mix(n010, n110, u.x), u.y),\n        mix(mix(n001, n101, u.x), mix(n011, n111, u.x), u.y),\n        u.z);\n\n    // Unit gradients ⇒ |n| ≤ √3/2. Scale to [-1, 1]; clamp covers FP error only.\n    return clamp(n * 1.15470053838, -1.0, 1.0);\n}\n\n\n\n@uniforms\n\n@snippet\n\nvoid main() {\n    vec2 st = gl_FragCoord.xy / u_resolution.xy;\n\n    @uv\n\n    float noise = noise2(st * 5.0) * 0.5 + 0.5;\n\n    vec3 v = @demo;\n    outColor = vec4(vec3(v), 1.0);\n}\n"}]

{"params":[{"label":"Direction","type":"point2d","uniform":"direction","value":{"true":0.5,"x":0}}],"previews":[{"code":{"demo":"vec3(noise)","uv":"st = Scroll(st, direction, u_time);"},"label":"Noise","template":"shaders/templates/noise.frag"}]}

Parameters:

uv the default uv to be manipulated.
direction defines the direction the uv should be panned.
time time since startup.

Use cases:

Effects: UV scrolling is used in everything from energy beams to waterfalls and conveyor belts.
Rim Lighting: Fresnel is also commonly used to achieve cheap rim lighting, especially in stylized character shaders.
Flowmaps: UV scrolling is an essential component of more advanced techniques like flowmaps.

Lerp

Inverse Lerp

Fresnel Ramp

UV Scrolling

Parameters:

Use cases:

Related