const canvas = document.getElementById("canvas");
const gl = canvas.getContext("webgl");
const vertexShaderSource = `
attribute vec4 a_position;
void main() {
gl_Position = a_position;
}
`;
const fragmentShaderSource = `
precision mediump float;
void main() {
gl_FragColor = vec4(1, 0, 0, 1);
}
`;
function createShader(gl, type, source) {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
return shader;
}
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSource);
const program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
gl.useProgram(program);
const positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
const positions = [
0, 0,
1, 0,
0, 1,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
const a_position = gl.getAttribLocation(program, "a_position");
gl.enableVertexAttribArray(a_position);
gl.vertexAttribPointer(a_position, 2, gl.FLOAT, false, 0, 0);
gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 3);