鴻蒙OS元服務開發案例：【WebGL網頁圖形庫開發著色器繪制彩色三角形】

著色器繪制彩色三角形

使用WebGL開發時，為保證界面圖形顯示效果，請使用真機運行。

此場景為使用WebGL繪制的彩色三角形圖形（GPU繪制）。開發示例如下：

創建頁面布局。index.hml示例如下：

< div class="container" >
< canvas ref="canvas1" style="width : 400px; height : 200px; background-color : lightyellow;" >< /canvas >
< button class="btn-button" onclick="BtnColorTriangle" >BtnColorTriangle< /button >
< /div >

1.設置頁面樣式。index.css示例如下：

.container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
}
.btn-button {
    margin: 1px;
    height: 40px;
    width: 220px;
    background-color: lightblue;
    font-size: 20px;
    text-color: blue;
}

2.編輯JavaScript代碼文件，增加彩色三角形繪制邏輯代碼。index.js示例如下：

// index.js

// WebGL相關預定義
var gl = {
    DEPTH_BUFFER_BIT: 0x00000100,
    STENCIL_BUFFER_BIT: 0x00000400,
    COLOR_BUFFER_BIT: 0x00004000,
    POINTS: 0x0000,
    LINES: 0x0001,
    LINE_LOOP: 0x0002,
    LINE_STRIP: 0x0003,
    TRIANGLES: 0x0004,
    TRIANGLE_STRIP: 0x0005,
    TRIANGLE_FAN: 0x0006,
    ZERO: 0,
    ONE: 1,
    SRC_COLOR: 0x0300,
    ONE_MINUS_SRC_COLOR: 0x0301,
    SRC_ALPHA: 0x0302,
    ONE_MINUS_SRC_ALPHA: 0x0303,
    DST_ALPHA: 0x0304,
    ONE_MINUS_DST_ALPHA: 0x0305,
    DST_COLOR: 0x0306,
    ONE_MINUS_DST_COLOR: 0x0307,
    SRC_ALPHA_SATURATE: 0x0308,
    FUNC_ADD: 0x8006,
    BLEND_EQUATION: 0x8009,
    BLEND_EQUATION_RGB: 0x8009,
    BLEND_EQUATION_ALPHA: 0x883D,
    FUNC_SUBTRACT: 0x800A,
    FUNC_REVERSE_SUBTRACT: 0x800B,
    BLEND_DST_RGB: 0x80C8,
    BLEND_SRC_RGB: 0x80C9,
    BLEND_DST_ALPHA: 0x80CA,
    BLEND_SRC_ALPHA: 0x80CB,
    CONSTANT_COLOR: 0x8001,
    ONE_MINUS_CONSTANT_COLOR: 0x8002,
    CONSTANT_ALPHA: 0x8003,
    ONE_MINUS_CONSTANT_ALPHA: 0x8004,
    BLEND_COLOR: 0x8005,
    ARRAY_BUFFER: 0x8892,
    ELEMENT_ARRAY_BUFFER: 0x8893,
    ARRAY_BUFFER_BINDING: 0x8894,
    ELEMENT_ARRAY_BUFFER_BINDING: 0x8895,
    STREAM_DRAW: 0x88E0,
    STATIC_DRAW: 0x88E4,
    DYNAMIC_DRAW: 0x88E8,
    BUFFER_SIZE: 0x8764,
    BUFFER_USAGE: 0x8765,
    CURRENT_VERTEX_ATTRIB: 0x8626,
    FRONT: 0x0404,
    BACK: 0x0405,
    FRONT_AND_BACK: 0x0408,
    CULL_FACE: 0x0B44,
    BLEND: 0x0BE2,
    DITHER: 0x0BD0,
    STENCIL_TEST: 0x0B90,
    DEPTH_TEST: 0x0B71,
    SCISSOR_TEST: 0x0C11,
    POLYGON_OFFSET_FILL: 0x8037,
    SAMPLE_ALPHA_TO_COVERAGE: 0x809E,
    SAMPLE_COVERAGE: 0x80A0,
    NO_ERROR: 0,
    INVALID_ENUM: 0x0500,
    INVALID_VALUE: 0x0501,
    INVALID_OPERATION: 0x0502,
    OUT_OF_MEMORY: 0x0505,
    CW: 0x0900,
    CCW: 0x0901,
    LINE_WIDTH: 0x0B21,
    ALIASED_POINT_SIZE_RANGE: 0x846D,
    ALIASED_LINE_WIDTH_RANGE: 0x846E,
    CULL_FACE_MODE: 0x0B45,
    FRONT_FACE: 0x0B46,
    DEPTH_RANGE: 0x0B70,
    DEPTH_WRITEMASK: 0x0B72,
    DEPTH_CLEAR_VALUE: 0x0B73,
    DEPTH_FUNC: 0x0B74,
    STENCIL_CLEAR_VALUE: 0x0B91,
    STENCIL_FUNC: 0x0B92,
    STENCIL_FAIL: 0x0B94,
    STENCIL_PASS_DEPTH_FAIL: 0x0B95,
    STENCIL_PASS_DEPTH_PASS: 0x0B96,
    STENCIL_REF: 0x0B97,
    STENCIL_VALUE_MASK: 0x0B93,
    STENCIL_WRITEMASK: 0x0B98,
    STENCIL_BACK_FUNC: 0x8800,
    STENCIL_BACK_FAIL: 0x8801,
    STENCIL_BACK_PASS_DEPTH_FAIL: 0x8802,
    STENCIL_BACK_PASS_DEPTH_PASS: 0x8803,
    STENCIL_BACK_REF: 0x8CA3,
    STENCIL_BACK_VALUE_MASK: 0x8CA4,
    STENCIL_BACK_WRITEMASK: 0x8CA5,
    VIEWPORT: 0x0BA2,
    SCISSOR_BOX: 0x0C10,
    COLOR_CLEAR_VALUE: 0x0C22,
    COLOR_WRITEMASK: 0x0C23,
    UNPACK_ALIGNMENT: 0x0CF5,
    PACK_ALIGNMENT: 0x0D05,
    MAX_TEXTURE_SIZE: 0x0D33,
    MAX_VIEWPORT_DIMS: 0x0D3A,
    SUBPIXEL_BITS: 0x0D50,
    RED_BITS: 0x0D52,
    GREEN_BITS: 0x0D53,
    BLUE_BITS: 0x0D54,
    ALPHA_BITS: 0x0D55,
    DEPTH_BITS: 0x0D56,
    STENCIL_BITS: 0x0D57,
    POLYGON_OFFSET_UNITS: 0x2A00,
    POLYGON_OFFSET_FACTOR: 0x8038,
    TEXTURE_BINDING_2D: 0x8069,
    SAMPLE_BUFFERS: 0x80A8,
    SAMPLES: 0x80A9,
    RGBA8: 0x8058,
    SAMPLE_COVERAGE_VALUE: 0x80AA,
    SAMPLE_COVERAGE_INVERT: 0x80AB,
    COMPRESSED_TEXTURE_FORMATS: 0x86A3,
    DONT_CARE: 0x1100,
    FASTEST: 0x1101,
    NICEST: 0x1102,
    GENERATE_MIPMAP_HINT: 0x8192,
    BYTE: 0x1400,
    UNSIGNED_BYTE: 0x1401,
    SHORT: 0x1402,
    UNSIGNED_SHORT: 0x1403,
    INT: 0x1404,
    UNSIGNED_INT: 0x1405,
    FLOAT: 0x1406,
    DEPTH_COMPONENT: 0x1902,
    ALPHA: 0x1906,
    RGB: 0x1907,
    RGBA: 0x1908,
    LUMINANCE: 0x1909,
    LUMINANCE_ALPHA: 0x190A,
    UNSIGNED_SHORT_4_4_4_4: 0x8033,
    UNSIGNED_SHORT_5_5_5_1: 0x8034,
    UNSIGNED_SHORT_5_6_5: 0x8363,
    FRAGMENT_SHADER: 0x8B30,
    VERTEX_SHADER: 0x8B31,
    MAX_VERTEX_ATTRIBS: 0x8869,
    MAX_VERTEX_UNIFORM_VECTORS: 0x8DFB,
    MAX_VARYING_VECTORS: 0x8DFC,
    MAX_COMBINED_TEXTURE_IMAGE_UNITS: 0x8B4D,
    MAX_VERTEX_TEXTURE_IMAGE_UNITS: 0x8B4C,
    MAX_TEXTURE_IMAGE_UNITS: 0x8872,
    MAX_FRAGMENT_UNIFORM_VECTORS: 0x8DFD,
    SHADER_TYPE: 0x8B4F,
    DELETE_STATUS: 0x8B80,
    LINK_STATUS: 0x8B82,
    VALIDATE_STATUS: 0x8B83,
    ATTACHED_SHADERS: 0x8B85,
    ACTIVE_UNIFORMS: 0x8B86,
    ACTIVE_ATTRIBUTES: 0x8B89,
    SHADING_LANGUAGE_VERSION: 0x8B8C,
    CURRENT_PROGRAM: 0x8B8D,
    NEVER: 0x0200,
    LESS: 0x0201,
    EQUAL: 0x0202,
    LEQUAL: 0x0203,
    GREATER: 0x0204,
    NOTEQUAL: 0x0205,
    GEQUAL: 0x0206,
    ALWAYS: 0x0207,
    KEEP: 0x1E00,
    REPLACE: 0x1E01,
    INCR: 0x1E02,
    DECR: 0x1E03,
    INVERT: 0x150A,
    INCR_WRAP: 0x8507,
    DECR_WRAP: 0x8508,
    VENDOR: 0x1F00,
    RENDERER: 0x1F01,
    VERSION: 0x1F02,
    NEAREST: 0x2600,
    LINEAR: 0x2601,
    NEAREST_MIPMAP_NEAREST: 0x2700,
    LINEAR_MIPMAP_NEAREST: 0x2701,
    NEAREST_MIPMAP_LINEAR: 0x2702,
    LINEAR_MIPMAP_LINEAR: 0x2703,
    TEXTURE_MAG_FILTER: 0x2800,
    TEXTURE_MIN_FILTER: 0x2801,
    TEXTURE_WRAP_S: 0x2802,
    TEXTURE_WRAP_T: 0x2803,
    TEXTURE_2D: 0x0DE1,
    TEXTURE: 0x1702,
    TEXTURE_CUBE_MAP: 0x8513,
    TEXTURE_BINDING_CUBE_MAP: 0x8514,
    TEXTURE_CUBE_MAP_POSITIVE_X: 0x8515,
    TEXTURE_CUBE_MAP_NEGATIVE_X: 0x8516,
    TEXTURE_CUBE_MAP_POSITIVE_Y: 0x8517,
    TEXTURE_CUBE_MAP_NEGATIVE_Y: 0x8518,
    TEXTURE_CUBE_MAP_POSITIVE_Z: 0x8519,
    TEXTURE_CUBE_MAP_NEGATIVE_Z: 0x851A,
    MAX_CUBE_MAP_TEXTURE_SIZE: 0x851C,
    TEXTURE0: 0x84C0,
    TEXTURE1: 0x84C1,
    TEXTURE2: 0x84C2,
    TEXTURE3: 0x84C3,
    TEXTURE4: 0x84C4,
    TEXTURE5: 0x84C5,
    TEXTURE6: 0x84C6,
    TEXTURE7: 0x84C7,
    TEXTURE8: 0x84C8,
    TEXTURE9: 0x84C9,
    TEXTURE10: 0x84CA,
    TEXTURE11: 0x84CB,
    TEXTURE12: 0x84CC,
    TEXTURE13: 0x84CD,
    TEXTURE14: 0x84CE,
    TEXTURE15: 0x84CF,
    TEXTURE16: 0x84D0,
    TEXTURE17: 0x84D1,
    TEXTURE18: 0x84D2,
    TEXTURE19: 0x84D3,
    TEXTURE20: 0x84D4,
    TEXTURE21: 0x84D5,
    TEXTURE22: 0x84D6,
    TEXTURE23: 0x84D7,
    TEXTURE24: 0x84D8,
    TEXTURE25: 0x84D9,
    TEXTURE26: 0x84DA,
    TEXTURE27: 0x84DB,
    TEXTURE28: 0x84DC,
    TEXTURE29: 0x84DD,
    TEXTURE30: 0x84DE,
    TEXTURE31: 0x84DF,
    ACTIVE_TEXTURE: 0x84E0,
    REPEAT: 0x2901,
    CLAMP_TO_EDGE: 0x812F,
    MIRRORED_REPEAT: 0x8370,
    FLOAT_VEC2: 0x8B50,
    FLOAT_VEC3: 0x8B51,
    FLOAT_VEC4: 0x8B52,
    INT_VEC2: 0x8B53,
    INT_VEC3: 0x8B54,
    INT_VEC4: 0x8B55,
    BOOL: 0x8B56,
    BOOL_VEC2: 0x8B57,
    BOOL_VEC3: 0x8B58,
    BOOL_VEC4: 0x8B59,
    FLOAT_MAT2: 0x8B5A,
    FLOAT_MAT3: 0x8B5B,
    FLOAT_MAT4: 0x8B5C,
    SAMPLER_2D: 0x8B5E,
    SAMPLER_CUBE: 0x8B60,
    VERTEX_ATTRIB_ARRAY_ENABLED: 0x8622,
    VERTEX_ATTRIB_ARRAY_SIZE: 0x8623,
    VERTEX_ATTRIB_ARRAY_STRIDE: 0x8624,
    VERTEX_ATTRIB_ARRAY_TYPE: 0x8625,
    VERTEX_ATTRIB_ARRAY_NORMALIZED: 0x886A,
    VERTEX_ATTRIB_ARRAY_POINTER: 0x8645,
    VERTEX_ATTRIB_ARRAY_BUFFER_BINDING: 0x889F,
    IMPLEMENTATION_COLOR_READ_TYPE: 0x8B9A,
    IMPLEMENTATION_COLOR_READ_FORMAT: 0x8B9B,
    COMPILE_STATUS: 0x8B81,
    LOW_FLOAT: 0x8DF0,
    MEDIUM_FLOAT: 0x8DF1,
    HIGH_FLOAT: 0x8DF2,
    LOW_INT: 0x8DF3,
    MEDIUM_INT: 0x8DF4,
    HIGH_INT: 0x8DF5,
    FRAMEBUFFER: 0x8D40,
    RENDERBUFFER: 0x8D41,
    RGBA4: 0x8056,
    RGB5_A1: 0x8057,
    RGB565: 0x8D62,
    DEPTH_COMPONENT16: 0x81A5,
    STENCIL_INDEX8: 0x8D48,
    DEPTH_STENCIL: 0x84F9,
    RENDERBUFFER_WIDTH: 0x8D42,
    RENDERBUFFER_HEIGHT: 0x8D43,
    RENDERBUFFER_INTERNAL_FORMAT: 0x8D44,
    RENDERBUFFER_RED_SIZE: 0x8D50,
    RENDERBUFFER_GREEN_SIZE: 0x8D51,
    RENDERBUFFER_BLUE_SIZE: 0x8D52,
    RENDERBUFFER_ALPHA_SIZE: 0x8D53,
    RENDERBUFFER_DEPTH_SIZE: 0x8D54,
    RENDERBUFFER_STENCIL_SIZE: 0x8D55,
    FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE: 0x8CD0,
    FRAMEBUFFER_ATTACHMENT_OBJECT_NAME: 0x8CD1,
    FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL: 0x8CD2,
    FRAMEBUFFER_ATTACHMENT_TEXTURE_CUBE_MAP_FACE: 0x8CD3,
    COLOR_ATTACHMENT0: 0x8CE0,
    DEPTH_ATTACHMENT: 0x8D00,
    STENCIL_ATTACHMENT: 0x8D20,
    DEPTH_STENCIL_ATTACHMENT: 0x821A,
    NONE: 0,
    FRAMEBUFFER_COMPLETE: 0x8CD5,
    FRAMEBUFFER_INCOMPLETE_ATTACHMENT: 0x8CD6,
    FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT: 0x8CD7,
    FRAMEBUFFER_INCOMPLETE_DIMENSIONS: 0x8CD9,
    FRAMEBUFFER_UNSUPPORTED: 0x8CDD,
    FRAMEBUFFER_BINDING: 0x8CA6,
    RENDERBUFFER_BINDING: 0x8CA7,
    MAX_RENDERBUFFER_SIZE: 0x84E8,
    INVALID_FRAMEBUFFER_OPERATION: 0x0506,
    UNPACK_FLIP_Y_WEBGL: 0x9240,
    UNPACK_PREMULTIPLY_ALPHA_WEBGL: 0x9241,
    CONTEXT_LOST_WEBGL: 0x9242,
    UNPACK_COLORSPACE_CONVERSION_WEBGL: 0x9243,
    BROWSER_DEFAULT_WEBGL: 0x9244,
    TEXTURE_MAX_LOD: 0x813B,
    TEXTURE_BASE_LEVEL: 0x813C,
    TEXTURE_IMMUTABLE_FORMAT: 0x912F,
    UNIFORM_BLOCK_BINDING: 0x8A3F,
    UNIFORM_BLOCK_DATA_SIZE: 0x8A40,
    UNIFORM_BLOCK_ACTIVE_UNIFORMS: 0x8A42,
    UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES: 0x8A43,
    UNIFORM_BLOCK_REFERENCED_BY_VERTEX_SHADER: 0x8A44,
    UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER: 0x8A46,
    RED: 0x1903,
    PIXEL_UNPACK_BUFFER: 0x88EC,
    RGB8: 0x8051,
    R16F: 0x822D,
    COPY_WRITE_BUFFER: 0x8F37,
    TEXTURE_3D: 0x806F,
    COMPRESSED_R11_EAC: 0x9270,
    COPY_READ_BUFFER: 0x8F36,
    TRANSFORM_FEEDBACK_BUFFER: 0x8C8E,
    TRANSFORM_FEEDBACK_BUFFER_BINDING: 0x8C8F,
    TRANSFORM_FEEDBACK_BUFFER_SIZE: 0x8C85,
    TRANSFORM_FEEDBACK_BUFFER_START: 0x8C84,
    UNIFORM_BUFFER_BINDING: 0x8A28,
    UNIFORM_BUFFER_SIZE: 0x8A2A,
    UNIFORM_BUFFER_START: 0x8A29,
    DYNAMIC_READ: 0x88E9,
    READ_FRAMEBUFFER: 0x8CA8,
    COLOR_ATTACHMENT1: 0x8CE1,
    INTERLEAVED_ATTRIBS: 0x8C8C,
    UNIFORM_OFFSET: 0x8A3B,
    UNIFORM_TYPE: 0x8A37,
    UNIFORM_SIZE: 0x8A38,
    UNIFORM_BLOCK_INDEX: 0x8A3A,
    UNIFORM_ARRAY_STRIDE: 0x8A3C,
    UNIFORM_MATRIX_STRIDE: 0x8A3D,
    UNIFORM_IS_ROW_MAJOR: 0x8A3E,
    TEXTURE_MAX_ANISOTROPY_EXT: 0x84FE
}

// 頂點著色器程序
var VSHADER_SOURCE =
    'attribute vec4 a_Position;n' + // attribute variable
    'attribute vec4 a_Color;n' +
    'varying vec4 v_Color;n' +
    'void main() {n' +
    '  gl_Position = a_Position;n' + // Set the vertex coordinates of the point
    '  v_Color = a_Color;n' +
    '}n';

// 片元著色器程序
var FSHADER_SOURCE =
    'precision mediump float;n' +
    'varying vec4 v_Color;n' +
    'void main() {n' +
    '  gl_FragColor = v_Color;n' +
    '}n';

function initVertexBuffers(gl) {
    // 頂點坐標和顏色
    var verticesColors = new Float32Array([
        0.0, -0.5, 1.0, 0.0, 0.0,
        -0.5, -0.8, 0.0, 1.0, 0.0,
        0.5, -0.8, 0.0, 0.0, 1.0,
    ]);

    var n = 3; // 點的個數
    var FSIZE = verticesColors.BYTES_PER_ELEMENT; //數組中每個元素的字節數

    // 創建緩沖區對象
    var vertexBuffer = gl.createBuffer();
    if (!vertexBuffer) {
        console.log('Failed to create the buffer object');
        return -1;
    }

    // 將緩沖區對象綁定到目標
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
    // 向緩沖區對象寫入數據
    gl.bufferData(gl.ARRAY_BUFFER, verticesColors.buffer, gl.STATIC_DRAW);

    // 獲取著色器中attribute變量a_Position的地址
    var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
    if (a_Position   0) {
        console.log('Failed to get the storage location of a_Position');
        return -1;
    }
    // 將緩沖區對象分配給a_Position變量
    gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 5 * FSIZE, 0);

    // 連接a_Position變量與分配給它的緩沖區對象
    gl.enableVertexAttribArray(a_Position);

    // 獲取著色器中attribute變量a_Color的地址
    var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
    if (a_Color   0) {
        console.log('Failed to get the storage location of a_Color');
        return -1;
    }
    // 將緩沖區對象分配給a_Color變量
    gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 5, FSIZE * 2);

    // 連接a_Color變量與分配給它的緩沖區對象
    gl.enableVertexAttribArray(a_Color);

    // 解除綁定
    gl.bindBuffer(gl.ARRAY_BUFFER, null);

    return n;
}

/**
 * 創建并使能一個program對象
 * @param gl 表示 WebGL上下文對
 * @param vshader 表示頂點著色器
 * @param fshader 表示片段著色器
 * @return 如果WebGLProgram對象被創建并成功作為當前對象，則返回true；否則返回false 
 */
function initShaders(gl, vshader, fshader) {
    var program = createProgram(gl, vshader, fshader);
    console.log("======createProgram program: " + program);

    if (!program) {
        console.log('Failed to create program');
        return false;
    }
    gl.useProgram(program);
    gl.program = program;

    return true;
}

/**
 * 創建一個linked program對象
 * @param gl 表示 WebGL上下文對象
 * @param vshader 表示頂點著色器
 * @param fshader 表示片段著色器
 * @return 如果創建program成功，則返回創建的program；否則返回null
 */
function createProgram(gl, vshader, fshader) {
    console.log("======createProgram start======");
    // 創建shader對象
    var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vshader);
    console.log("======vertexShader: " + vertexShader);
    var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fshader);
    if (!vertexShader || !fragmentShader) {
        return null;
    }

    // 創建program對象
    var program = gl.createProgram();
    console.log("======createProgram program: " + program);

    if (!program) {
        return null;
    }

    // 將著色器附加到對象
    gl.attachShader(program, vertexShader);
    gl.attachShader(program, fragmentShader);

    // 連接程序對象
    gl.linkProgram(program);

    // 檢查連接對象的結果
    var linked = gl.getProgramParameter(program, 0x8B82);
    console.log("======getProgramParameter linked: " + linked);

    if (!linked) {
        var error = gl.getProgramInfoLog(program);
        console.log('Failed to link the program: ' + error);
        gl.deleteProgram(program);
        gl.deleteShader(fragmentShader);
        gl.deleteShader(vertexShader);
        return null;
    }
    return program;
}

/**
  * 創建一個shader對象
  * @param gl 表示 WebGL上下文對象
  * @param type 表示shader類型
  * @param source 表示shader的源碼 
  * @return 如果操作成功，返回創建的著色器對象；否則返回false
  */ 
function loadShader(gl, type, source) {
    console.log("======into loadShader====");
    // 創建shader對象
    var shader = gl.createShader(type);
    if (shader == null) {
        console.log('Failed to create the shader.');
        return null;
    }

    // 設置shader program
    gl.shaderSource(shader, source);

    // 編譯shader
    gl.compileShader(shader);

    // 檢查shader編譯結果
    var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
    if (!compiled) {
        var error = gl.getShaderInfoLog(shader);
        console.log('Failed to compile the shader: ' + error);
        gl.deleteShader(shader);
        return null;
    }

    return shader;
}

export default {
    data: {
        title: "DEMO BY TEAMOL",
        fit:"cover",
        fits: ["cover", "contain", "fill", "none", "scale-down"]
    }
    ,onInit() {
        this.title = this.$t('strings.world');
    }
    ,BtnColorTriangle() {
        // 獲取canvas元素
        const el = this.$refs.canvas1;
        // 獲取webgl上下文
        var gl = el.getContext('webgl');

        if (!gl) {
            console.log('Failed to get the rendering context for WebGL');
            return;
        }

        // 初始化著色器
        if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
            console.log('Failed to initialize shaders.');
            return;
        }

        // 設置頂點位置
        var n = initVertexBuffers(gl);
        if (n   0) {
            console.log('Failed to set the positions of the vertices');
            return;
        }

        // 指定清空 canvas >的顏色
        gl.clearColor(0.0, 0.0, 0.0, 1.0);

        // 清空 canvas >
        gl.clear(gl.COLOR_BUFFER_BIT);

        // 繪制三角形
        gl.drawArrays(gl.TRIANGLES, 0, n);

        // 清buffer
        gl.flush();
    }
}```

![搜狗高速瀏覽器截圖20240326151547.png](//file1.elecfans.com/web2/M00/C5/CD/wKgZomYCdwyAIFf5AAB_7E1pFms943.jpg)

### 3.點擊按鈕繪制彩色三角形的效果圖

![01.png](//file1.elecfans.com/web2/M00/C7/91/wKgaomYLq9-AJEtiAAAnMeNXZtI569.jpg)

審核編輯 黃宇