webgl 三角形绘制

Posted 2021-09-04 diuxie

<canvas id="myCanvas" ></canvas>
var canvas = document.getElementById(\'myCanvas\')
var gl = canvas.getContext(\'webgl\')
var program = gl.createProgram()
var VSHADER_SOURCE, FSHADER_SOURCE

VSHADER_SOURCE =
\'attribute vec4 a_Position;\\n\' +
\'uniform mat4 u_ModelMatrix;\\n\' +
\'uniform mat4 u_ViewMatrix;\\n\' +
\'void main () {\\n\' +
\'gl_Position = u_ProjectionMartix u_ViewMatrix u_ModelMatrix * a_Position; \\n\' +
\'}\\n\'
FSHADER_SOURCE =
\'void main () {\\n\' +
\'gl_FragColor = vec4(1.0,0.0,0.0,1.0);\\n\' +
\'}\\n\'
var vertexShader, fragmentShader
function createShader (gl, sourceCode, type) {
// create shader
var shader = gl.createShader(type)
gl.shaderSource(shader,sourceCode)
gl.compileShader(shader)
return shader
}
// define vertex shader
vertexShader = createShader(gl, VSHADER_SOURCE,gl.VERTEX_SHADER)
//define frament shader
fragmentShader = createShader(gl, FSHADER_SOURCE, gl.FRAGMENT_SHADER)

//attach shader to program
gl.attachShader(program, vertexShader)
gl.attachShader(program, fragmentShader)

//link program to context
gl.linkProgram(program)
gl.useProgram(program)
gl.program = program

var currentAngle = 0
var g_last = Date.now()

var tick = function () {
// update the new rotation angle
animate()
//draw
draw()
requestAnimationFrame(tick)
}
function initVertexBuffers (gl) {
var vertices = new Float32Array([

0, 0.5, -0.5, -0.5, 0.5, -0.5

])
var n = 3
var vertexBuffer = www.cungun.comgl.createBuffer()
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer)
// write data into the buffer object
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW)
// get attribute a_Position address in vertex shader
var a_Position = gl.getAttribLocation(gl.program, \'a_Position\')
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0)
// enable a_Position variable
gl.enableVertexAttribArray(a_Position)
return n
}
// write the positions of vertices to a vertex shader
var n = initVertexBuffers(gl)

gl.clearColor(0, 0, 0, 1)

var u_ModelMatrix = gl.getUniformLocation(gl.program, \'u_ModelMatrix\')
var modelMatrix = new Matrix4()

然后调取出游戏数据库：
var u_ViewMatrix = gl.getUniformLocation(gl.program, \'u_ViewMatrix\')
var viewMatrix = new Matrix4()
viewMatrix.lookAt(100, 100, 100, 0, 0, 0, 0, 1, 0)

var u_ProjectionMatrix = gl.getUniformLocation(gl.program, \'u_ProjectionMatrix\')
var projectionMatrix = new Matrix4()
// projectionMatrix.perspective(120, 1, 0.1, 1000)
projectionMatrix.ortho(-1, 1, -1, 1, 0.1, 1000)

function animate () {
var now = Date.now()
var duration = now - g_last
g_last = now
currentAngle = currentAngle + duration / 1000 * 180
}

function draw () {
// clear canvas and add background color
modelMatrix.setRotate(currentAngle, 0, 1, 0)
gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements)
gl.uniformMatrix4fv(u_ViewMatrix, false, viewMatrix.elements)
gl.uniformMatrix4fv(u_ProjectionMatrix, false, projectionMatrix.elements)
gl.clear(gl.COLOR_BUFFER_BIT)
gl.drawArrays(gl.TRIANGLES, 0, n)
}

tick()