情人节玫瑰花
使用了多個不同的形狀圖來組成這朵代碼玫瑰。共使用了 31 個形狀：24 個花瓣，4 個萼片，2 個葉子和 1 根花莖，其中每一個形狀圖都用代碼進行描繪。
首先，來定義一個采樣范圍：
<script> function surface(a, b) { // 使用 a 和 b 作為采樣范圍的參數return {x: a*50,y: b*50};// 該表面是一個 50*50 單元區域 } </script>編寫形狀描繪代碼：
<script> var canvas = document.body.appendChild(document.createElement("canvas")),context = canvas.getContext("2d"),a, b, position;for (a = 0; a < 1; a += .1) {for (b = 0; b < 1; b += .1) {position = surface(a, b);context.fillRect(position.x, position.y, 1, 1);} } </script>看到的效果是這樣的：
看到的效果是這樣的：
因為采樣間隔越來越密集，點越來越接近，到最高密度時，相鄰點之間的距離小于一個像素，肉眼就看不到間隔（見 0.01）。為了不造成太大的視覺差，再進一步縮小采樣間隔，此時，繪制區已經填滿（比較結果為 0.01 和 0.001）。
接下來，我用這個公式來繪制一個圓形：（X-X0）^ 2 +（Y-Y0）^ 2 <半徑^ 2，其中（X0，Y0）為圓心：
<script> function surface(a, b) {var x = a * 100,y = b * 100,radius = 50,x0 = 50,y0 = 50;if ((x - x0) * (x - x0) + (y - y0) * (y - y0) < radius * radius) {// 圓內return {x: x,y: y};} else {// 圓外return null;} } </script>為了防止溢出，還要加上一個采樣條件
<script> if (position = surface(a, b)) {context.fillRect(position.x, position.y, 1, 1); } </script>現在讓圓變形，以使它看起來更像是一個花瓣：
<script> function surface(a, b) {var x = a * 100,y = b * 100,radius = 50,x0 = 50,y0 = 50;if ((x - x0) * (x - x0) + (y - y0) * (y - y0) < radius * radius) {return {x: x,y: y * (1 + b) / 2 // 變形 };} else {return null;} }添加色彩
<script> function surface(a, b) {var x = a * 100,y = b * 100,radius = 50,x0 = 50,y0 = 50;if ((x - x0) * (x - x0) + (y - y0) * (y - y0) < radius * radius) {return {x: x,y: y * (1 + b) / 2,r: 100 + Math.floor((1 - b) * 155), // 添加梯度g: 50,b: 50};} else {return null;} }for (a = 0; a < 1; a += .01) {for (b = 0; b < 1; b += .001) {if (point = surface(a, b)) {context.fillStyle = "rgb(" + point.r + "," + point.g + "," + point.b + ")";context.fillRect(point.x, point.y, 1, 1);}} }3D 曲面和透視投影
定義三維表面
<script> function surface(a, b) {var angle = a * Math.PI * 2,radius = 100,length = 400;return {x: Math.cos(angle) * radius,y: Math.sin(angle) * radius,z: b * length - length / 2, // 減去一般的長度，使得焦點在三維坐標中心點(0,0,0)r: 0,g: Math.floor(b * 255),b: 0}; } </script>添加投影透視圖
<script> var pX, pY, // 畫布 X 和 Y 軸的坐標perspective = 350,halfHeight = canvas.height / 2,halfWidth = canvas.width / 2,cameraZ = -700;for (a = 0; a < 1; a += .001) {for (b = 0; b < 1; b += .01) {if (point = surface(a, b)) {pX = (point.x * perspective) / (point.z - cameraZ) + halfWidth;pY = (point.y * perspective) / (point.z - cameraZ) + halfHeight;context.fillStyle = "rgb(" + point.r + "," + point.g + "," + point.b + ")";context.fillRect(pX, pY, 1, 1);}} } </script>z-buffer
在為物件進行著色時，執行“隱藏面消除”工作，使隱藏物件背后的部分就不會被顯示出來。
<script> var zBuffer = [],zBufferIndex;for (a = 0; a < 1; a += .001) {for (b = 0; b < 1; b += .01) {if (point = surface(a, b)) {pX = Math.floor((point.x * perspective) / (point.z - cameraZ) + halfWidth);pY = Math.floor((point.y * perspective) / (point.z - cameraZ) + halfHeight);zBufferIndex = pY * canvas.width + pX;if ((typeof zBuffer[zBufferIndex] === "undefined") || (point.z < zBuffer[zBufferIndex])) {zBuffer[zBufferIndex] = point.z;context.fillStyle = "rgb(" + point.r + "," + point.g + "," + point.b + ")";context.fillRect(pX, pY, 1, 1);}}} } </script>旋轉-歐拉旋轉
將之前編寫的管狀物進行旋轉，實現繞 Y 軸旋轉：
<script>var angle = a * Math.PI * 2,radius = 100,length = 400,x = Math.cos(angle) * radius,y = Math.sin(angle) * radius,z = b * length - length / 2,yAxisRotationAngle = -.4, // 弧度rotatedX = x * Math.cos(yAxisRotationAngle) + z * Math.sin(yAxisRotationAngle),rotatedZ = x * -Math.sin(yAxisRotationAngle) + z * Math.cos(yAxisRotationAngle);return {x: rotatedX,y: y,z: rotatedZ,r: 0,g: Math.floor(b * 255),b: 0}; } </script>關于采樣時間，間隔過大過小都會引起極差的視覺感受，所以，需要設置合理的采樣間隔，這里使用蒙特卡羅方法。
<script> var i;window.setInterval(function () {for (i = 0; i < 10000; i++) {if (point = surface(Math.random(), Math.random())) {pX = Math.floor((point.x * perspective) / (point.z - cameraZ) + halfWidth);pY = Math.floor((point.y * perspective) / (point.z - cameraZ) + halfHeight);zBufferIndex = pY * canvas.width + pX;if ((typeof zBuffer[zBufferIndex] === "undefined") || (point.z < zBuffer[zBufferIndex])) {zBuffer[zBufferIndex] = point.z;context.fillStyle = "rgb(" + point.r + "," + point.g + "," + point.b + ")";context.fillRect(pX, pY, 1, 1);}}} }, 0); </script>完整版
<!DOCTYPE HTML> <html> <head> <title>Rose</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body style="margin-left:200px"> <div style="text-align: center"> <canvas id="c"></canvas> </div><script type="text/javascript">var canvas = document.getElementsByTagName('canvas')[0];var context = canvas.getContext('2d'); var a = context; var b = document.body;var c = canvas;document.body.clientWidth; var zBuffer = []; var SIZE = 777;canvas.width = canvas.height = SIZE;var h = -350; function surface(a, b, c) { if (c > 60) { return { x : Math.sin(a * 7) * (13 + 5 / (.2 + Math.pow(b * 4, 4))) - Math.sin(b) * 50, y : b * SIZE + 50, z : 625 + Math.cos(a * 7) * (13 + 5 / (.2 + Math.pow(b * 4, 4))) + b * 400, r : a * 1 - b / 2, g : a }; } var A = a * 2 - 1;var B = b * 2 - 1; if (A * A + B * B < 1) {if (c > 37) { var j = c & 1; var n = j ? 6 : 4; var o = .5 / (a + .01) + Math.cos(b * 125) * 3 - a * 300; var w = b * h; return { x : o * Math.cos(n) + w * Math.sin(n) + j * 610 - 390, y : o * Math.sin(n) - w * Math.cos(n) + 550 - j * 350, z : 1180 + Math.cos(B + A) * 99 - j * 300, r : .4 - a * .1 + Math.pow(1 - B * B, -h * 6) * .15 - a * b * .4 + Math.cos(a + b) / 5 + Math.pow(Math.cos((o * (a + 1) + (B > 0 ? w : -w)) / 25), 30) * .1 * (1 - B * B), g : o / 1e3 + .7 - o * w * 3e-6}; }if (c > 32) { c = c * 1.16 - .15; var o = a * 45 - 20; var w = b * b * h; var z = o * Math.sin(c) + w * Math.cos(c) + 620; return { x : o * Math.cos(c) - w * Math.sin(c), y : 28 + Math.cos(B * .5) * 99 - b * b * b * 60 - z / 2 - h, z : z, r : (b * b * .3 + Math.pow((1 - (A * A)), 7) * .15 + .3) * b, g : b * .7 }; }var o = A * (2 - b) * (80 - c * 2); var w = 99 - Math.cos(A) * 120 - Math.cos(b) * (-h - c * 4.9) + Math.cos(Math.pow(1 - b, 7)) * 50 + c * 2; var z = o * Math.sin(c) + w * Math.cos(c) + 700; return { x : o * Math.cos(c) - w * Math.sin(c), y : B * 99 - Math.cos(Math.pow(b, 7)) * 50 - c / 3 - z / 1.35 + 450, z : z, r : (1 - b / 1.2) * .9 + a * .1, g : Math.pow((1 - b), 20) / 4 + .05 }; } } setInterval(function() { for ( var i = 0; i < 10000; i++) { var part = i % 46; var c = part / .74; var point = surface(Math.random(), Math.random(), c); if (point) { var z = point.z; var x = parseInt(point.x * SIZE / z - h); var y = parseInt(point.y * SIZE / z - h); var zBufferIndex = y * SIZE + x; if ((typeof zBuffer[zBufferIndex] === "undefined") || (zBuffer[zBufferIndex] > z)) { zBuffer[zBufferIndex] = z; var r = -parseInt(point.r * h); var g = -parseInt(point.g * h); var b = -parseInt(point.r * point.r * -80); context.fillStyle = "rgb(" + r + "," + g + "," + b + ")"; context.fillRect(x, y, 1, 1); } } } }, 0); </script></body> </html>轉載于:https://www.cnblogs.com/baby123/p/5065623.html
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