var vertexSource = '' +
'attribute vec4 a_Position;' +
'void main(){' +
' gl_PointSize = 10.0;' +
' gl_Position = a_Position;' +
'}';
var fragmentSource = '' +
'void main(){' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);' +
'}';
var canvas = document.getElementById('canvas')
var gl = canvas.getContext('webgl')
var vertexShader = gl.createShader(gl.VERTEX_SHADER)
var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER)
gl.shaderSource(vertexShader, vertexSource)
gl.shaderSource(fragmentShader, fragmentSource)
gl.compileShader(vertexShader)
gl.compileShader(fragmentShader)
var program = gl.createProgram()
gl.attachShader(program, vertexShader)
gl.attachShader(program, fragmentShader)
gl.linkProgram(program)
gl.useProgram(program)
var n = 4
var vertices = new Float32Array([
-0.5, 0.5, -0.5, -0.5, 0.5, 0.5, 0.5, -0.5
])
var vertexBuffer = gl.createBuffer()
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer)
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW)
var a_position = gl.getAttribLocation(program, 'a_Position')
gl.vertexAttribPointer(a_position, 2, gl.FLOAT, false, 0, 0)
gl.enableVertexAttribArray(a_position)
gl.clearColor(0, 0, 0, 1)
gl.clear(gl.COLOR_BUFFER_BIT)
gl.drawArrays(gl.POINTS, 0, 4)
setTimeout(() => {
gl.clear(gl.COLOR_BUFFER_BIT)
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4)
}, 5000)