前言
很多游戏都有一些高逼格的屏幕特效，一些3D引擎是通过场景渲染到UI上，甚至直接是一个场景。但也有其他的方法可以实现，比如纯Shader。
我借鉴了https://www.shadertoy.com/view/XtfSW4
方法和之前的文章类似就不赘述了，感兴趣的同学可以看看。
代码分享
shader_type canvas_item;
uniform vec3 iResolution; // 视口分辨率(像素)
uniform float iTime; // 着色器回放时间(单位:秒)
const float cloudDensity = 1.0; // overall density [0,1]
const float noisiness = 0.35; // overall strength of the noise effect [0,1]
const float speed = 0.1; // controls the animation speed [0, 0.1 ish)
const float cloudHeight = 2.5; // (inverse) height of the input gradient [0,...)
// Simplex noise below = ctrl+c, ctrl+v:
// Description : Array and textureless GLSL 2D/3D/4D simplex
// noise functions.
// Author : Ian McEwan, Ashima Arts.
// Maintainer : ijm
// Lastmod : 20110822 (ijm)
// License : Copyright (C) 2011 Ashima Arts. All rights reserved.
// Distributed under the MIT License. See LICENSE file.
// https://github.com/ashima/webgl-noise
//
vec3 mod289(vec3 x) {
return x - floor(x * (1.0 / 289.0)) * 289.0;
}
vec4 mod289_(vec4 x) {
return x - floor(x * (1.0 / 289.0)) * 289.0;
}
vec4 permute(vec4 x) {
return mod289_(((x*34.0)+1.0)*x);
}
vec4 taylorInvSqrt(vec4 r)
{
return 1.79284291400159 - 0.85373472095314 * r;
}
float snoise(vec3 v)
{
const vec2 C = vec2(1.0/6.0, 1.0/3.0) ;
const vec4 D = vec4(0.0, 0.5, 1.0, 2.0);
// First corner
vec3 i = floor(v + dot(v, C.yyy) );
vec3 x0 = v - i + dot(i, C.xxx) ;
// Other corners
vec3 g = step(x0.yzx, x0.xyz);
vec3 l = 1.0 - g;
vec3 i1 = min( g.xyz, l.zxy );
vec3 i2 = max( g.xyz, l.zxy );
// x0 = x0 - 0.0 + 0.0 * C.xxx;
// x1 = x0 - i1 + 1.0 * C.xxx;
// x2 = x0 - i2 + 2.0 * C.xxx;
// x3 = x0 - 1.0 + 3.0 * C.xxx;
vec3 x1 = x0 - i1 + C.xxx;
vec3 x2 = x0 - i2 + C.yyy; // 2.0*C.x = 1/3 = C.y
vec3 x3 = x0 - D.yyy; // -1.0+3.0*C.x = -0.5 = -D.y
// Permutations
i = mod289(i);
vec4 p = permute( permute( permute(
i.z + vec4(0.0, i1.z, i2.z, 1.0 ))
+ i.y + vec4(0.0, i1.y, i2.y, 1.0 ))
+ i.x + vec4(0.0, i1.x, i2.x, 1.0 ));
// Gradients: 7x7 points over a square, mapped onto an octahedron.
// The ring size 17*17 = 289 is close to a multiple of 49 (49*6 = 294)
float n_ = 0.142857142857; // 1.0/7.0
vec3 ns = n_ * D.wyz - D.xzx;
vec4 j = p - 49.0 * floor(p * ns.z * ns.z); // mod(p,7*7)
vec4 x_ = floor(j * ns.z);
vec4 y_ = floor(j - 7.0 * x_ ); // mod(j,N)
vec4 x = x_ *ns.x + ns.yyyy;
vec4 y = y_ *ns.x + ns.yyyy;
vec4 h = 1.0 - abs(x) - abs(y);
vec4 b0 = vec4( x.xy, y.xy );
vec4 b1 = vec4( x.zw, y.zw );
//vec4 s0 = vec4(lessThan(b0,0.0))*2.0 - 1.0;
//vec4 s1 = vec4(lessThan(b1,0.0))*2.0 - 1.0;
vec4 s0 = floor(b0)*2.0 + 1.0;
vec4 s1 = floor(b1)*2.0 + 1.0;
vec4 sh = -step(h, vec4(0.0));
vec4 a0 = b0.xzyw + s0.xzyw*sh.xxyy ;
vec4 a1 = b1.xzyw + s1.xzyw*sh.zzww ;
vec3 p0 = vec3(a0.xy,h.x);
vec3 p1 = vec3(a0.zw,h.y);
vec3 p2 = vec3(a1.xy,h.z);
vec3 p3 = vec3(a1.zw,h.w);
//Normalise gradients
vec4 norm = taylorInvSqrt(vec4(dot(p0,p0), dot(p1,p1), dot(p2, p2), dot(p3,p3)));
p0 *= norm.x;
p1 *= norm.y;
p2 *= norm.z;
p3 *= norm.w;
// Mix final noise value
vec4 m = max(0.6 - vec4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.0);
m = m * m;
return 42.0 * dot( m*m, vec4( dot(p0,x0), dot(p1,x1),
dot(p2,x2), dot(p3,x3) ) );
}
/// Cloud stuff:
const float maximum = 1.0/1.0 + 1.0/2.0 + 1.0/3.0 + 1.0/4.0 + 1.0/5.0 + 1.0/6.0 + 1.0/7.0 + 1.0/8.0;
// Fractal Brownian motion, or something that passes for it anyway: range [-1, 1]
float fBm(vec3 uv)
{
float sum = 0.0;
for (int i = 0; i < 8; ++i) {
float f = float(i+1);
sum += snoise(uv*f) / f;
}
return sum / maximum;
}
// Simple vertical gradient:
float gradient(vec2 uv) {
return (1.0 - uv.y * uv.y * cloudHeight);
}
vec4 mainImage(in vec4 fragCoord )
{
vec2 uv = fragCoord.xy / iResolution.xy;
vec3 p = vec3(uv, iTime*speed);
vec3 someRandomOffset = vec3(0.1, 0.3, 0.2);
vec2 duv = vec2(fBm(p), fBm(p + someRandomOffset)) * noisiness;
float q = gradient(uv + duv) * cloudDensity;
q = clamp(q,0.0, 1.0);
return vec4(q,q,q, q);
}
void fragment(){
vec4 output = mainImage(FRAGCOORD);
COLOR = output;
}总结
我改动了几处，godot引擎中没有mainImage函数，所以需要把改函数放进fragment函数中。
并且对mainImage函数的定义进行了修改，比如void变成vec4。
增加了两个变量，用于程序修改
uniform vec3 iResolution; // 视口分辨率(像素)
uniform float iTime; // 着色器回放时间(单位:秒)对一些变量写上了const
const float cloudDensity = 1.0; // overall density [0,1]
const float noisiness = 0.35; // overall strength of the noise effect [0,1]
const float speed = 0.1; // controls the animation speed [0, 0.1 ish)
const float cloudHeight = 2.5; // (inverse) height of the input gradient [0,...)以及修改重名函数mod289_
vec4 mod289_(vec4 x) {
return x - floor(x * (1.0 / 289.0)) * 289.0;
}
vec4 permute(vec4 x) {
return mod289_(((x*34.0)+1.0)*x);
}最后放出效果
