By using the following: function initVertexBuffers (gl){ var vertices = new Float32Array ([ 0.50,0.0,0.25,0.50,0.0,0.0,0.25,0.50,0.50,0.0 ]); var n=5;// The number of vertices gl.drawArrays (gl. LINES_LOOP, 0, 3); gl.drawArrays(gl.TRIANGLES, 2, 3); Draw the corresponding shape