Question

在尝试创建createRegularPolygon函数时，我遇到了一个无法让它呈现的问题。它会抛出一个错误，告诉我我试图访问超出范围的顶点。

[.Offscreen-For-WebGL-0x7f8c4a89c400] GL错误：GL_INVALID_OPERATION：glDrawElements：尝试访问属性0中超出范围的顶点

以下是我生成几何体的代码，下面将是整个测试代码。以下代码的某些内容会破坏格式

export const createRegularPolygon =
  (gl: WebGLRenderingContext) =>
    (position: [number, number], sides: number, radius: number): FlatGeometry | null => {

      const points: number[] = [...position, 0];
      const indices = [];
      let i = -1;
      while (++i <= sides) {
        const segment = i * 2 * Math.PI / sides;
        points.push(
          radius * Math.cos(segment) + position[0],
          radius * Math.sin(segment) + position[1],
          0,
        );
      }
      i = 0;
      while (++i <= sides) indices.push(i, i + 1, 0);

      const verticiesBufferData = new Float32Array(points);
      const verticiesBuffer = gl.createBuffer();
      gl.bindBuffer(gl.ARRAY_BUFFER, verticiesBuffer);
      gl.bufferData(
        gl.ARRAY_BUFFER,
        verticiesBufferData,
        gl.STATIC_DRAW,
      );
      gl.bindBuffer(gl.ARRAY_BUFFER, null);


      const indicesBufferData = new Float32Array(indices);
      const indicesBuffer = gl.createBuffer();
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indicesBuffer);
      gl.bufferData(
        gl.ELEMENT_ARRAY_BUFFER,
        indicesBufferData,
        gl.STATIC_DRAW,
      );
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);

      if (!verticiesBuffer || !indicesBuffer) return null;

      return {
        verticies: verticiesBuffer,
        indices: indicesBuffer,
        size: indices.length,
      };
    };

以下是已编译的代码：

(function () {
'use strict';

function reduce(array, func, base) {
    let i = -1;
    while (++i < array.length)
        base = func(base, array[i], i, array);
    return base;
}

const map = (array, func) => reduce(array, (result, value, index, array) => add(result, func(value, index, array)), []);


const flatten = (array) => [].concat(...array);

const copy = (array) => array.slice(0);

const add = (array, value, index = 0) => {
    const result = copy(array);
    result.splice(index, 0, value);
    return result;
};

const createTriangle = (gl) => (points) => {
    const vertices = flatten(map(points, pnt => [...pnt, 0]));
    const vertexBuffer = gl.createBuffer();
    if (!vertexBuffer)
        return null;
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    const indexBuffer = gl.createBuffer();
    if (!indexBuffer)
        return null;
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    return {
        verticies: vertexBuffer,
        indices: indexBuffer,
        size: 3,
    };
};

const createRectangle = (gl) => (width, height = width) => {
    const vertices = [
        -width / 2, height / 2, 0,
        width / 2, height / 2, 0,
        -width / 2, -height / 2, 0,
        width / 2, -height / 2, 0,
    ];
    const vertexBuffer = gl.createBuffer();
    if (!vertexBuffer)
        return null;
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    const indexBuffer = gl.createBuffer();
    if (!indexBuffer)
        return null;
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 1, 3, 2]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    return {
        verticies: vertexBuffer,
        indices: indexBuffer,
        size: 6,
    };
};

const createRegularPolygon = (gl) => (position, sides, radius) => {
    const points = [...position, 0];
    const indices = [];
    let i = -1;
    while (++i <= sides) {
        const segment = i * 2 * Math.PI / sides;
        points.push(radius * Math.cos(segment) + position[0], radius * Math.sin(segment) + position[1], 0);
    }
    i = 0;
    while (++i <= sides)
        indices.push(i, i + 1, 0);
    const verticiesBufferData = new Float32Array(points);
    const verticiesBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, verticiesBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, verticiesBufferData, gl.STATIC_DRAW);
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    const indicesBufferData = new Float32Array(indices);
    const indicesBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indicesBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indicesBufferData, gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    if (!verticiesBuffer || !indicesBuffer)
        return null;
    console.log(verticiesBufferData, indicesBufferData);
    return {
        verticies: verticiesBuffer,
        indices: indicesBuffer,
        size: indices.length,
    };
};

const draw = (gl) => (shader) => (geometry) => {
    gl.useProgram(shader.program);
    gl.bindBuffer(gl.ARRAY_BUFFER, geometry.verticies);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, geometry.indices);
    gl.vertexAttribPointer(shader.attribLocations.vertexPosition, 3, gl.FLOAT, false, 0, 0);
    gl.enableVertexAttribArray(shader.attribLocations.vertexPosition);
    gl.drawElements(gl.TRIANGLES, geometry.size, gl.UNSIGNED_SHORT, 0);
    gl.disableVertexAttribArray(shader.attribLocations.vertexPosition);
};

const createShaderLoader = (gl) => (type, source) => {
    const shader = gl.createShader(type);
    gl.shaderSource(shader, source);
    gl.compileShader(shader);
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        gl.deleteShader(shader);
        return null;
    }
    return shader;
};

const createShader = (gl) => (vsSource, fsSource) => {
    const loadShader = createShaderLoader(gl);
    const vertexShader = loadShader(gl.VERTEX_SHADER, vsSource);
    const fragmentShader = loadShader(gl.FRAGMENT_SHADER, fsSource);
    const shaderProgram = gl.createProgram();
    gl.attachShader(shaderProgram, vertexShader);
    gl.attachShader(shaderProgram, fragmentShader);
    gl.linkProgram(shaderProgram);
    if (!shaderProgram || !gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
        return null;
    }
    return {
        program: shaderProgram,
        attribLocations: {
            vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
        },
        uniformLocations: {
            projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
            modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
        }
    };
};

const vs = `
    attribute vec4 aVertexPosition;

    void main() {
      gl_Position = aVertexPosition;
    }
`;
const fs = `
    void main() {
      gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
    }
`;

function main(gl) {
    if (!gl)
        return false;
    gl.clearColor(0.0, 0.0, 0.0, 1.0);
    gl.clearDepth(1.0);
    gl.enable(gl.DEPTH_TEST);
    gl.depthFunc(gl.LEQUAL);
    gl.clear(gl.COLOR_BUFFER_BIT);
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
    const polygonT = createTriangle(gl)([[-1, 1], [-1, -1], [1, -1]]);
    const polygonP = createRegularPolygon(gl)([0, 0], 3, 0.5);
    const polygonR = createRectangle(gl)(2, 0.25);
    const defaultShader = createShader(gl)(vs, fs);
    if (!defaultShader || !polygonT || !polygonR || !polygonP)
        return false;
    [polygonP].forEach(draw(gl)(defaultShader));
    return true;
}

const canvas = document.querySelector(`canvas`);
if (canvas) {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    const gl = canvas.getContext('webgl');
    if (gl)
        main(gl);
}

}());

<html>
<style>
  html,
  body {
    width: 100%;
    height: 100%;
  }
  html,
  body,
  canvas {
    padding: 0;
    margin: 0;
  }
</style>

<body>
  <canvas></canvas>
</body>

</html>

Answer 1

这个错误只是一个错字

const indicesBufferData = new Float32Array(indices);

中的这一行

const indicesBufferData = new Uint16Array(indices);

应该是这个

FROM  i386/ubuntu:17.04

WebGl：Draw Circle遇到错误（在里面指定）

1 个答案: