shadertoy的一款分形山脉

原创
2017/03/06 18:07
阅读数 945

在 shadertoy.com 上发现一款挺不错的分形山脉, 改写到 Codea 中, 代码如下:

function setup()
    parameter.watch("1/DeltaTime")
    
    local tex1 = readImage("Dropbox:3D-grass2")

    m1 = mesh()
    m1.shader=shader(f.vs,f.fs)
    m1.shader.iResolution = vec3(1000,1000,100)
    m1.shader.iChannel0 = tex1
    m1:addRect(WIDTH/2,HEIGHT/2,WIDTH/1,HEIGHT/1)
end

function draw()
    m1.shader.iGlobalTime = ElapsedTime
    m1:draw()
end

f = {
vs = [[

uniform mat4 modelViewProjection;

attribute vec4 position;
attribute vec4 color;
attribute vec2 texCoord;

//This is an output variable that will be passed to the fragment shader
varying lowp vec4 vColor;
varying highp vec2 vTexCoord;

void main()
{
    //Pass the mesh color to the fragment shader
    vColor = color;
    vTexCoord = texCoord;
    
    //Multiply the vertex position by our combined transform
    gl_Position = modelViewProjection * position;
}
]],

fs = [[

// from https://www.shadertoy.com/view/llsGW7#

precision highp float;

uniform lowp sampler2D texture;

uniform vec3      iResolution;           // viewport resolution (in pixels)
uniform float     iGlobalTime;           // shader playback time (in seconds)
uniform lowp sampler2D iChannel0;          // input channel. XX = 2D/Cube

#define F +texture2D(iChannel0,.3+p.xz*(s+=s)/6e3,-99.)/s

void main()
{
   vec4 p=vec4(gl_FragCoord.xy/iResolution.xy,1,1)-.5, d=p*.5, t;
    p.z += iGlobalTime*20.; d.y-=.2;

    for(float i=1.7;i>=0.;i-=.002)
    {
        float s=.5;
        //t=F+F+F+F+F+F;
        t = F F F F F F;
/*
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
    t+= texture2D(iChannel0,.3+p.xw*s/6e3,-99.)/s;s+=s;
*/
        gl_FragColor = vec4(1,.9,.8,9)+d.x-t*i;
        if(t.x>p.y*.01+1.3)break;
        p += d;
    }
}

]]
}

结果发现FPS太低, 居然比不上 WebGL下的帧速, 正在分析原因, 显示效果:

输入图片说明

shadertoy 用的纹理:

输入图片说明

shadertoy 中的效果:

输入图片说明

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