【发布时间】：2018-10-28 03:50:02
【问题描述】：
我正在学习 WebGL 技术。不幸的是我遇到了一些错误。我想为直升机绘制二维两个形状。我在下面写了代码。正是我想做的就是在一个叫做主体的形状上制作一个螺旋桨。
请注意，我尝试创建一个新缓冲区并绑定它，但仍然失败。我觉得stride还没搞懂，但我想学习如何解决它，即使它很简单。
// Vertex shader
var _vertexShader = `
attribute vec4 _position;
void main() {
gl_Position = _position;
}
`
// Fragment shader
var _fragmentShader = `
precision mediump float;
void main() {
gl_FragColor = vec4(0.6, 0.8, 0.3, 1);
}
`
// Create shader
function createShader(gl, type, source) {
var shader = gl.createShader(type)
gl.shaderSource(shader, source)
gl.compileShader(shader)
var success = gl.getShaderParameter(shader, gl.COMPILE_STATUS)
if (success) {
return shader
} else {
console.log(gl.getShaderInfoLog(shader))
gl.deleteShader(shader)
// return false
}
}
// Linking shader by program
function createProgram(gl, vertexShader, fragmentShader) {
var program = gl.createProgram()
gl.attachShader(program, vertexShader)
gl.attachShader(program, fragmentShader)
gl.linkProgram(program)
var success = gl.getProgramParameter(program, gl.LINK_STATUS)
if (success) {
return program
} else {
console.log(gl.getProgramInfoLog(program))
gl.deleteProgram(program)
// return false
}
}
function main() {
// Get a WebGL context.
var canvas = document.getElementById('canvas')
var gl = canvas.getContext('webgl2')
if (!gl) {
alert('Not support.')
return false
}
// Get the strings for our GLSL shaders.
var vertexShader = createShader(gl, gl.VERTEX_SHADER, _vertexShader)
var fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, _fragmentShader)
// Link the two shaders into a program.
var program = createProgram(gl, vertexShader, fragmentShader)
// Look up where the vertex data need to go.
var positionLoc = gl.getAttribLocation(program, '_position')
// Create a buffer and put the three 2d clip space points in it.
var body_positionBuf = gl.createBuffer()
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = body_positionBuf).
gl.bindBuffer(gl.ARRAY_BUFFER, body_positionBuf)
var body_positions = new Float32Array(
[
// Body triangle (Right)
-0.25, 0,
0.25, 0,
0, 0.5,
// Body triangle (Left)
-0.15, 0,
0.15, 0,
0.15, -0.25,
// Body square
-0.15, 0,
-0.15, -0.25,
0.15, -0.25,
]
)
var roter_positions = new Float32Array([
0.15, 0.1,
0.15, -0.1,
-0.15, 0.1,
-0.15, -0.1,
-0.15, 0.1,
0.15, 0.1,
])
gl.bufferData(gl.ARRAY_BUFFER, body_positions, gl.STATIC_DRAW)
// Code above this line is initialization code.
// Code below this line is rendering code.
// webglUtils.resizeCanvasToDisplaySize(gl.canvas)
// Tell WebGL how to convert from clip space to pixels.
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height)
// Clear the canvas.
gl.clearColor(0, 0, 0, 0)
gl.clear(gl.COLOR_BUFFER_BIT)
// Tell it to use our program (pair of shaders).
gl.useProgram(program)
// Turn on the attribute.
gl.enableVertexAttribArray(positionLoc)
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, body_positionBuf)
// Tell the attribute how to get data out of body_positionBuf (ARRAY_BUFFER).
var size = 2
var type = gl.FLOAT
var normalize = false
var stride = 0
var offset = 0
gl.vertexAttribPointer(positionLoc, size, type, normalize, stride, offset)
// Draw.
var drawType = gl.TRIANGLES
var count = body_positions.length / 2
gl.drawArrays(drawType, offset, count)
}
main()<canvas id="canvas" width="500" height="250"></canvas>我该怎么办？我不知道..请帮助我，谢谢。
【问题讨论】：
-
您必须创建第二个缓冲区。当你想绘图时，你必须绑定缓冲区
gl.bindBuffer，定义顶点属性gl.vertexAttribPointer，最后是进行绘图调用gl.drawArrays。这 3 个步骤您必须对这两个对象执行。 -
如果您只想使用 1 个缓冲区，那么您已经定义了一个足够大的数据存储，可以容纳两个数组
gl.bufferData。通过gl.bufferSubData将两个数组的数据添加到缓冲区中。 -
@Rabbid76 谢谢。我有一些问题。顶点着色器代码相同..？对不起..我不明白..
-
@Rabbid76 我可以看看一些代码的例子吗？
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