上篇采用了HTML5的Canvas的globalCompositeOperation属性达到了染色效果,其实CSS也提供了一些常规图像变化的设置参数,关于CSS的过滤器Filter设置可参考 ,CSS的设置的确很方便,不需要我们了解底层实现逻辑,仅需要提供简单的设置参数值即可,但这样的方式毕竟无法达到随心所欲变化的效果,这有点想OpenGL早期只能通过Fixed Function Pipeline进行开发,和如今采用Shading Language可实现丰富多彩变化的质变,因此这篇我们将采用WebGL的SL代码方式折腾点更好玩的效果。
在第一篇我们已经提到图像操作的本质是对输入输出的数据变化,因此染色仅是最简单直观的基本变化,通过WebGL的SL代码我们甚至可以实现图像扭曲等变化效果,先上张最终变化效果的截图,原图就是的banner,染色+扭曲的效果如上:
Vertex代码如下:
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attribute vec2 aVertexPosition;
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attribute vec2 aTexturePosition;
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varying vec2 vTexturePosition;
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void main() {
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vTexturePosition = aTexturePosition;
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gl_Position = vec4(aVertexPosition, 0.0, 1.0);
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}
Fragment代码如下:
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precision mediump float;
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varying vec2 vTexturePosition;
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uniform sampler2D uSampler;
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uniform vec4 uColor;
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uniform float uRadius;
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uniform float uAngle;
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uniform vec2 uCenter;
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void main() {
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vec2 vec = vTexturePosition - uCenter;
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float distance = length(vec);
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if (distance < uRadius) {
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float ratio = (uRadius - distance) / uRadius;
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float angle = ratio * ratio * uAngle;
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float s = sin(angle);
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float c = cos(angle);
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vec = vec2(vec.x * c - vec.y * s, vec.x * s + vec.y * c);
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}
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gl_FragColor = texture2D(uSampler, uCenter+vec) * uColor;
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}
相应JavaScript代码如下:
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gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
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gl.clearColor(0.0, 0.0, 0.0, 1.0);
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gl.clear(gl.COLOR_BUFFER_BIT);
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vertexShader = loadShaderFromDOM("shader-vs");
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fragmentShader = loadShaderFromDOM("shader-fs");
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var program = gl.createProgram();
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gl.attachShader(program, vertexShader);
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gl.attachShader(program, fragmentShader);
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gl.linkProgram(program);
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gl.useProgram(program);
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var vertexBuffer = gl.createBuffer();
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gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
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gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
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-0.7, 0.7,
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-0.7, -0.7,
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0.7, 0.7,
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-0.7, -0.7,
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0.7, -0.7,
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0.7, 0.7
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]), gl.STATIC_DRAW);
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var vertexLocation = gl.getAttribLocation(program, "aVertexPosition");
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gl.vertexAttribPointer(vertexLocation, 2, gl.FLOAT, false, 0, 0);
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gl.enableVertexAttribArray(vertexLocation);
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var textureBuffer = gl.createBuffer();
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gl.bindBuffer(gl.ARRAY_BUFFER, textureBuffer);
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gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
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0, 1,
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0, 0,
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1, 1,
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0, 0,
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1, 0,
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1, 1
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]), gl.STATIC_DRAW);
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var textureLocation = gl.getAttribLocation(program, "aTexturePosition");
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gl.vertexAttribPointer(textureLocation, 2, gl.FLOAT, false, 0, 0);
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gl.enableVertexAttribArray(textureLocation);
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gl.activeTexture(gl.TEXTURE0);
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gl.bindTexture(gl.TEXTURE_2D, texture);
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gl.uniform1i(gl.getUniformLocation(program, 'uSampler'), 0);
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gl.uniform4fv(gl.getUniformLocation(program, 'uColor'), toRGBA(formPane.v('color')));
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gl.uniform1f(gl.getUniformLocation(program, 'uRadius'), formPane.v('radius'));
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gl.uniform1f(gl.getUniformLocation(program, 'uAngle'), formPane.v('angle'));
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gl.uniform2fv(gl.getUniformLocation(program, 'uCenter'), [formPane.v('centerX'), 1-formPane.v('centerY')]);
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gl.drawArrays(gl.TRIANGLES, 0, 6);
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}
以上Vertext和Fragment的代码很多很容易理解,采用的很容易实现控制参数面板可进行编辑实时呈现变化效果,以下为操作控制面板动态变化的视频效果:
最后如果你耐心细致地阅读到此,对前端游戏开发感兴趣,感觉自己悟性不错,愿意在厦门发展的同学可与联系我,我的邮箱为eric@… 省略部分你应该知道的,不限制性别、学历和年龄,只要你想用心做自己喜欢的事,我期待着与你交流和加盟!
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