Question

我正在更新现有的WebGl代码（仅具有关于WebGl的非常基本的知识）。在代码中，有几个函数可以增加一组这样的缓冲区

this.tail = new Float32Array(0);
this.tail_buffer = gl.createBuffer();
this.tail_index = 0;
this.tail_colors = new Float32Array(0);
this.tail_colors_buffer = gl.createBuffer();
var length = 512;   
this.head = new Float32Array(0);
this.head_buffer = gl.createBuffer();
this.tail_length = new Float32Array(0);

/**
 * Update the tail buffer between two indexes.
 * @param {number} a, with a <= b
 * @param {number} b
 */
_update = function(a, b) {
    var gl = this.gl;
    var length = 512;
    var buffer = this.tail.buffer;
    gl.bindBuffer(gl.ARRAY_BUFFER, this.tail_buffer);
    if (a == 0 && b == length - 1) {
        gl.bufferSubData(gl.ARRAY_BUFFER, 0, this.tail);
    } else {
        var sublength = b - a + 1;
        for (var s = 0; s < this.solutions.length; s++)  {
            var offset = s * 3 * length * 4 + 3 * a * 4;
            var view = new Float32Array(buffer, offset, sublength * 3);
            gl.bufferSubData(gl.ARRAY_BUFFER, offset, view);
        }
    }
};

/**
 * Adjust all buffer sizes if needed.
 */
_grow_buffers = function() {
    function next2(x) {
        return Math.pow(2, Math.ceil(Math.log(x) * Math.LOG2E));
    }
    var gl = this.gl;
    var count = next2(some_number);
    var length = 512;
    if (this.tail.length < count * length * 3) {
        var old_tail = this.tail;
        this.tail = new Float32Array(count * length * 3);
        this.tail.set(old_tail);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.tail_buffer);
        gl.bufferData(gl.ARRAY_BUFFER, count * length * 4 * 3, gl.DYNAMIC_DRAW);
        this._update(0, length - 1);
    }
    if (this.tail_length.length < count) {
        var old_tail_length = this.tail_length;
        this.tail_length = new Float32Array(count);
        this.tail_length.set(old_tail_length);
    }
    if (this.tail_colors.length < count * 3) {
        this.tail_colors = new Float32Array(count * 3);
        for (var i = 0; i < this.tail_colors.length; i++) {
            var color = getColor(i);
            this.tail_colors[i * 3 + 0] = color[0];
            this.tail_colors[i * 3 + 1] = color[1];
            this.tail_colors[i * 3 + 2] = color[2];
        }
        gl.bindBuffer(gl.ARRAY_BUFFER, this.tail_colors_buffer);
        gl.bufferData(gl.ARRAY_BUFFER, count * 4 * 3, gl.STATIC_DRAW);
        gl.bufferSubData(gl.ARRAY_BUFFER, 0, this.tail_colors);
    }
    if (this.head.length < count * 3) {
        this.head = new Float32Array(count * 3);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.head_buffer);
        gl.bufferData(gl.ARRAY_BUFFER, count * 3 * 4, gl.DYNAMIC_DRAW);
    }
};

我想写一个缩小缓冲区的函数（而不是像上面那样增加缓冲区）。最简单的方法是使用类似于grow_buffers函数的函数，但是将if语句还原（从<到>）。我想我虽然丢失了一些东西，但可能无法释放所有缓冲区空间。

有些我在上面的代码中不了解：gl.bufferSubData会做什么？在乘以3 * 4的过程中，我不理解4（3可能是颜色的数量）

动态缩小缓冲区

0 个答案: