LayaBox1.8.4实现UV滚动

实现思路：

在片元着色器采样时，增加一个随时间变化的偏移值，由于uv是一个二维向量所以加的偏移值也需要一个二维向量。注意：在Laya的 shader中除了0，输入其它数字必须输入带有小数的数字，否则报错 。

    "void main()\n" +
    "{\n" +
         "vec2 v = vec2(u_time * u_speed,0);\n"+
         "gl_FragColor=texture2D(u_Texture0, v_Texcoord + v) ;\n" +
     "}";

实现效果如下：

shader代码：

        //所有的attributeMap属性
        var attributeMap = {
            'a_Position': Laya.VertexElementUsage.POSITION0,
            'a_Texcoord': Laya.VertexElementUsage.TEXTURECOORDINATE0,    
        };
        //所有的uniform属性
        var uniformMap =
        {
            'u_MvpMatrix': [Laya.Sprite3D.MVPMATRIX, Laya.Shader3D.PERIOD_SPRITE],   
            'u_Texture0': [1, Laya.Shader3D.PERIOD_MATERIAL],
            'u_time':[22,Laya.Shader3D.PERIOD_SCENE],
            'u_speed':[4,Laya.Shader3D.PERIOD_MATERIAL],
        };
    
        var customShader = Laya.Shader3D.nameKey.add("CustomShader")
    
        var VS =
            "attribute vec4 a_Position;\n" +
            "uniform mat4 u_MvpMatrix;\n" +
            "attribute vec2 a_Texcoord;\n"+
            "varying vec2 v_Texcoord;\n" +

            "void main()\n" +
            "{\n" +
            "v_Texcoord = a_Texcoord;\n" +
            "gl_Position = u_MvpMatrix * a_Position;\n" +
            "}\n";
    
        var FS =
            "#ifdef FSHIGHPRECISION\n" +
            "precision highp float;\n" +
            "#else\n" +
            "precision mediump float;\n" +
            "#endif\n" +

            "varying vec2 v_Texcoord;\n" +
            "uniform sampler2D u_Texture0;\n"+ 
            "uniform float u_time;\n"+
            "uniform float u_speed;\n" +

            "void main()\n" +
            "{\n" +
            "vec2 v = vec2(u_time * u_speed,0);\n"+
            "gl_FragColor=texture2D(u_Texture0, v_Texcoord + v) ;\n" +
            "}";
        
    Laya.ShaderCompile3D.add(customShader, VS, FS, attributeMap, uniformMap);
    }

调用代码：

    CustomMat.initShader();
    var mat = new CustomMat();
    mat.setTexture(Laya.Texture2D.load("res/layabox.png"));
    mat.setSpeed(1);
    mat.blend = Laya.BaseMaterial.BLEND_ENABLE_SEPERATE;
    mesh.meshRender.sharedMaterial = mat;