webGL入门（六）图形旋转

news2024/11/24 9:43:36

效果：

代码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var webgl
        // shader参数
        var vsString = `
            attribute vec3 a_position;
            uniform float angle;
            void main(){
                gl_Position = vec4(a_position.x*cos(angle)-a_position.y*sin(angle),a_position.x*sin(angle)+a_position.y*cos(angle),0,1.0);
            }
        ` // 顶点着色器字符串
        var fsString = `
            void main(){
                gl_FragColor = vec4(1.0,0.0,0.0,1.0);
            }
        ` // 片元着色器字符串
        function init(){
            initWebgl()
            initShader()
            initBuffer()
            draw()
        }
        function initWebgl(){
            let webglDiv = document.getElementById('webgl_canvas')
            webgl = webglDiv.getContext("webgl")
            webgl.viewport(0,0,webglDiv.clientWidth,webglDiv.clientHeight)
        }
        function initShader(){
            // 创建shader
            let shaderVS = webgl.createShader(webgl.VERTEX_SHADER)
            let shaderFS = webgl.createShader(webgl.FRAGMENT_SHADER)

            // 绑定shader字符串
            webgl.shaderSource(shaderVS,vsString)
            webgl.shaderSource(shaderFS,fsString)

            // 编译shader
            webgl.compileShader(shaderVS)
            webgl.compileShader(shaderFS)

            // 判断shader是否编译成功
            let program = webgl.createProgram()
            webgl.attachShader(program,shaderVS)
            webgl.attachShader(program,shaderFS)

            // 链接program
            webgl.linkProgram(program)
            webgl.useProgram(program)
            webgl.program = program
        }
        function initBuffer(){
            let arr = [
                0.1,0.4,0.0,
                0.1,0.5,0.0,
                0.2,0.4,0.0,
            ]
            let float = new Float32Array(arr)
            let buffer = webgl.createBuffer()
            webgl.bindBuffer(webgl.ARRAY_BUFFER,buffer)
            webgl.bufferData(webgl.ARRAY_BUFFER,float,webgl.STATIC_DRAW)

            let aPosition = webgl.getAttribLocation(webgl.program,"a_position")
            webgl.vertexAttribPointer(aPosition,3,webgl.FLOAT,false,0,0)
            webgl.enableVertexAttribArray(aPosition)

            let uAngle = webgl.getUniformLocation(webgl.program,"angle")
            let angle1 = 90 * Math.PI / 180
            webgl.uniform1f(uAngle,angle1)
        }
        function draw(){
            webgl.clearColor(0.0,1.0,1.0,1.0)
            webgl.clear(webgl.COLOR_BUFFER_BIT)
            webgl.drawArrays(webgl.TRIANGLES,0,3)
        }
    </script>
</head>
<body onload="init()">
    <canvas id="webgl_canvas" width="500" height="500"></canvas>
</body>
</html>