PolyDraw/polyDraw.html at master · suekam/PolyDraw · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
<html>
	<head>
		<style>
			body {
				margin: 0;
				overflow: hidden;
			}
		</style>

		<script src="FileSaver.min.js" type="text/javascript"></script>

		<script id="shader-fs" type="x-shader/x-fragment">
			varying highp vec4 vColor;

			void main(void) {
				gl_FragColor = vColor;
			}
		</script>

		<script id="shader-vs" type="x-shader/x-vertex">
			/* Vertex positions */
			attribute vec3 aVertexPosition;
			attribute vec3 aVertexColor;
			varying highp vec4 vColor;

			void main(void) {
				gl_PointSize = 10.0;
				gl_Position = vec4(aVertexPosition, 1.0);
				vColor = vec4(aVertexColor, 1.0);
			}
		</script>

		<script type="text/javascript">
			/* canvas control */
			var canvas, ctx;
			drawingMode = true;
			editingMode = false;
			dragging = null;

			/* list of vertices for webGL and vertex accounting */
			var vertices = [];
			var vertexList = [];
			var vertexRaw = [];

			/* WebGL control */
			var gl = null, glProgram = null;
			var vertexShader = null, fragmentShader = null;
			var polygonVertexPositionBuffer = null;
			var polygonVertexColorBuffer = null;

			/* Mouse click handler */
			function onClickHandler(event) {
				if(drawingMode) {
					/* calcaulate relative position in viewport coord system, push to vertex list */
		   			glPosX = (((event.clientX - canvas.offsetLeft - window.pageXOffset) / canvas.width) - 0.5) * 2.0;
					glPosY = (((canvas.height - (event.clientY - canvas.offsetTop - window.pageYOffset)) / canvas.height) - 0.5) * 2.0;
					vertices.push(glPosX, glPosY, 0.0);
					vertexList.push([glPosX, glPosY, 0.0]);
					vertexRaw.push([event.clientX, event.clientY, 0.0]);

					/* draw point being clicked */
					updateWebGL();
					updateVertexBuffer();
					updateColorBuffer([1.0, 1.0, 1.0]);
					drawScene(gl.POINTS);
				}
			}

			/* key down listener */
			function onMouseDownHandler(event) {
				if(editingMode) {
					console.log("mouse down "+event.clientX+" "+event.clientY);
					for(var i=0; i<vertexRaw.length; i++) {
						if(event.clientX>(vertexRaw[i][0]-5.0) && event.clientX<(vertexRaw[i][0]+5.0) &&
								(event.clientY>(vertexRaw[i][1]-5.0) && (event.clientY<vertexRaw[i][1]+5.0))) {
							dragging=i;
							break;
						}
					}
					console.log(dragging);
				}
			}

			/* drag */
			function onMouseMoveHandler(event) {
				if(editingMode && dragging!=null) {
					/* record new canvas position */
					vertexRaw[dragging][0] = event.clientX;
					vertexRaw[dragging][1] = event.clientY;

					/* calcaulate relative position in viewport coord system, push to vertex list */
		   			vertexList[dragging][0] = (((event.clientX - canvas.offsetLeft - window.pageXOffset) / canvas.width) - 0.5) * 2.0;
					vertexList[dragging][1] = (((canvas.height - (event.clientY - canvas.offsetTop - window.pageYOffset)) / canvas.height) - 0.5) * 2.0;

					/* update WebGL vertex position buffer */
					vertices = [];
					for(var i=0; i<vertexList.length; i++) {
						vertices.push(vertexList[i][0], vertexList[i][1], 0.0);
					}
					updateWebGL();
					updateVertexBuffer();
					updateColorBuffer([0.0, 1.0, 0.0]);
					drawScene(gl.POINTS);
				}
			}

			/* mouse up handler */
			function onMouseUpHandler(event) {
				if(editingMode && dragging!=null) {
					console.log("onMouseUpHandler");
					dragging = null;
					console.log("dragging "+dragging);
				}
			}

			/* Key press handler */
			function onKeydownHandler(event) {
				switch(event.keyCode) {
					case 27:
						/* Esc key */
						if(!editingMode && !drawingMode) {
							/* terminate program by removing all event listeners */
							canvas.removeEventListener("click", onClickHandler);
							canvas.removeEventListener("mousedown", onMouseDownHandler);
							canvas.removeEventListener("mousemove", onMouseMoveHandler);
							canvas.removeEventListener("mouseup", onMouseUpHandler);

							window.removeEventListener("keydown", onKeydownHandler);
							window.removeEventListener("resize", windowResizeHandler);

							alert("Program terminated!");
						}
						else if(checkPolygon()) {
							/* update states */
							editingMode = false;
							drawingMode = false;

							/* clear canvas, bind vertex and color buffer, draw points and polygon */
							updateWebGL();
							updateVertexBuffer();
							updateColorBuffer([1.0, 0.0, 0.0]);
							drawScene(gl.TRIANGLE_FAN);
							updateColorBuffer([0.0, 1.0, 0.0]);
							drawScene(gl.POINTS);
						}
						else {
							/* fail to pass simple polygon validity check, alert user, clear list and clear canvas */
							alert("Polygon invalid!");
							editingMode = false;
							drawingMode = true;
							vertices = [];
							vertexList = [];
							vertexRaw = [];
							updateWebGL();
						}
						break;
					case 68:
						/* d key, drawing mode */
						editingMode = false;
						drawingMode = true;

						/* initialize canvas, clear vertex list and clear canvas */
						vertices = [];
						vertexList = [];
						vertexRaw = [];
						updateWebGL();
						break;
					case 83:
						if(checkPolygon()) {
							var blob = new Blob([vertexList], {type: "text/plain;charset=utf-8"});
							saveAs(blob, "polygon.txt");
						}
						else {
							alert("Invalid polygon!");
						}
						break;
					case 86:
						/* e key, reposition mode */
						editingMode = true;
						drawingMode = false;
						updateWebGL();
						updateVertexBuffer();
						drawScene(gl.POINTS);
						break;

				}
				console.log(event.keyCode);
			}


			/* initialize shader programs */
			function initShaders() {
				/* create vertex and fragment shaders */
				vertexShader = gl.createShader(gl.VERTEX_SHADER);
				fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);

				/* bind shader to glsl */
				gl.shaderSource(vertexShader, document.getElementById("shader-vs").innerHTML);
				gl.shaderSource(fragmentShader, document.getElementById("shader-fs").innerHTML);

				/* compile and check vertex shader */
				gl.compileShader(vertexShader);
				if (!gl.getShaderParameter(vertexShader, gl.COMPILE_STATUS)) {
					alert("Cannot compile vertex shader!");
				}

				/* compile and check fragment shader */
				gl.compileShader(fragmentShader);
				if(!gl.getShaderParameter(fragmentShader, gl.COMPILE_STATUS)) {
					alert("Cannot compile fragment shader!");
				}

				/* create GL program and link shaders */
				glProgram = gl.createProgram();

				gl.attachShader(glProgram, vertexShader);
				gl.attachShader(glProgram, fragmentShader);

				gl.linkProgram(glProgram);
				if (!gl.getProgramParameter(glProgram, gl.LINK_STATUS)) {
					alert("Unable to initialize the shader program.");
				}

				//use program
				gl.useProgram(glProgram);
			}

			/* create vertex buffers */
			function initBuffers() {
				/* create positon buffer */
				polygonVertexPositionBuffer = gl.createBuffer();

				/* create color buffer */
				polygonVertexColorBuffer = gl.createBuffer();
			}

			/* update vertex buffer */
			function updateVertexBuffer() {
				/* populate vertex position buffer with vertext list */
				gl.bindBuffer(gl.ARRAY_BUFFER, polygonVertexPositionBuffer);
				gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
				polygonVertexPositionBuffer.itemSize = 3;
				polygonVertexPositionBuffer.numItem = vertices.length / polygonVertexPositionBuffer.itemSize;
			}

			/* update color buffer */
			function updateColorBuffer(rgb) {
				/* generate color for each vertex */
				var colors = [];
				for(var i=0; i<polygonVertexPositionBuffer.numItem; i++)
					colors.push(rgb[0], rgb[1], rgb[2], 1.0);

				/* populate vertex color buffer with color list */
				gl.bindBuffer(gl.ARRAY_BUFFER, polygonVertexColorBuffer);
				gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
				polygonVertexColorBuffer.itemSize = 4;
				polygonVertexColorBuffer.numItem = colors.length / polygonVertexColorBuffer.itemSize;
			}

			/* setup viewport and clear view port with black */
			function updateWebGL() {
				gl.viewport(0, 0, canvas.width, canvas.height);
				gl.clearColor(0.0, 0.0, 0.0, 1.0);
				gl.clear(gl.COLOR_BUFFER_BIT);
			}

			/* draw from array */
			function drawScene(type) {
				/* bind and populate vertex positions */
				gl.vertexPositionAttribute = gl.getAttribLocation(glProgram, "aVertexPosition");
				gl.enableVertexAttribArray(gl.vertexPositionAttribute);
				gl.bindBuffer(gl.ARRAY_BUFFER, polygonVertexPositionBuffer);
				gl.vertexAttribPointer(gl.vertexPositionAttribute, polygonVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

				/* bind and populate vertex color */
				gl.vertexColorAttribute = gl.getAttribLocation(glProgram, "aVertexColor");
				gl.enableVertexAttribArray(gl.vertexColorAttribute);
				gl.bindBuffer(gl.ARRAY_BUFFER, polygonVertexColorBuffer);
				gl.vertexAttribPointer(gl.vertexColorAttribute, polygonVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

				/* draw from array */
				gl.drawArrays(type, 0, polygonVertexPositionBuffer.numItem);

			}

			/* check if polygon is valid */
			function checkPolygon() {
				/* extract the number of vertices in list */
				var numVertex = vertexList.length;

				/* if polygon is a triagle, must be valid; if it has less than 2 points, must be invalid */
				if(numVertex<3)
					return false;
				else if(numVertex==3)
					return true;

				/* define variable for next two vectors for edge pairs */
				var nextVector, nextNextVector;
				var crossProduct;
				var dX = [];
				var dY = [];
				var sign;

				/* iterate vertex list, determine pairwise cross product */
				for(var i=0; i<numVertex; i++) {
					/* get next to vertex index */
					nextVector = (i+1)%numVertex;
					nextNextVector = (i+2)%numVertex;

					/* individual diff */
					dX[0] = vertexList[nextVector][0] - vertexList[i][0];
					dY[0] = vertexList[nextVector][1] - vertexList[i][1];
					dX[1] = vertexList[nextNextVector][0] - vertexList[nextVector][0];
					dY[1] = vertexList[nextNextVector][1] - vertexList[nextVector][1];

					/* cross product */
					crossProduct = dX[0]*dY[1] - dX[1]*dY[0];
					console.log(crossProduct);

					if(i==0)
						/* all signs of cross product should follow the 1st pair */
						sign = crossProduct > 0 ? true : false;

					/* check if sign match the previous ones */
					if(sign) {
						if(crossProduct < 0)
							return false;
					}
					else {
						if(crossProduct > 0)
							return false;
					}
				}

				/* test passed, return true */
				return true;
			}

			/* on window size */
			function windowResizeHandler() {
				console.log("resize");
				init();
				updateVertexBuffer();
				updateColorBuffer([1.0, 0.0, 0.0]);
				drawScene(gl.TRIANGLE_FAN);
				updateColorBuffer([0.0, 1.0, 0.0]);
				drawScene(gl.POINTS);
			}

			/* on load */
			function init() {
				/* get canvas and WebGL context */
				canvas = document.getElementById("test-canvas");
				canvas.width = window.innerWidth;
				canvas.height = window.innerHeight;
				gl = canvas.getContext("experimental-webgl");

				/* Browser does not support WebGL */
				if(!gl) {
					alert("Browser does not support WebGL!");
				}

				/* initialize shaders and buffers and viewport */
				initShaders();
				initBuffers();
				updateWebGL();

				/* add event listeners for mouse-click and keydown */
				canvas.addEventListener("click", onClickHandler);
				canvas.addEventListener("mousedown", onMouseDownHandler);
				canvas.addEventListener("mousemove", onMouseMoveHandler);
				canvas.addEventListener("mouseup", onMouseUpHandler);

				window.addEventListener("keydown", onKeydownHandler);
				window.addEventListener("resize", windowResizeHandler);
			}

		</script>
	</head>
	<body height="100%" onload="init()">
		<canvas id="test-canvas" width="100%" height="100%"></canvas>
	</body>
</html>