那里有做网站的,网页设计工资一般多少钱一小时,昆明网站运营,凡客网站建设#xff08;一#xff09;Bloom介绍
Bloom#xff08;辉光、光晕、泛光#xff09;是一种常见的摄像机后处理#xff08;PostProcessing#xff09;效果#xff0c;用于再现真实世界相机的成像伪影。这种效果会产生从图像中明亮区域边界延伸的光条纹#xff08;或羽毛…一Bloom介绍
Bloom辉光、光晕、泛光是一种常见的摄像机后处理PostProcessing效果用于再现真实世界相机的成像伪影。这种效果会产生从图像中明亮区域边界延伸的光条纹或羽毛从而产生一种极其明亮的光线压倒捕捉场景的相机的错觉。
辉光简单的说法就是有些地方足够亮看上去是溢出到周围的区域下面是playcanvas官方提供的辉光效果对比图 图1 未使用辉光效果 图2 使用辉光效果
二Bloom实现原理 bloom的实现原理很简单就是取camera获取图像的高亮部分进行高斯模糊并和原图进行合并就可以实现。
1. 提取较亮区域
通过阈值提取较亮区域的像素点
varying vec2 vUv0;uniform sampler2D uBaseTexture
uniform float uBloomThreshold;float luminance(vec4 color)
{return 0.2125 * color[0] 0.7154 * color[1] 0.0721 * color[2];
}void main(void)
{vec4 color texture2D(uBaseTexture, vUv0);// 只保留亮度超过阈值亮度的像素点float val clamp(luminance(color) - uBloomThreshold, 0.0, 1.0);gl_FragColor color * val;//这是playcanvas官网提供提取亮度高于某个阈值的算法但还不知道它的原理//gl_FragColor clamp((color - uBloomThreshold) / (1.0 - uBloomThreshold), 0.0, 1.0);
}
2. 高斯模糊
接下来就是如何得到模糊图uBloomTexture
一般模糊图像的算法我们可以选择常见的高斯模糊它可以减少图像噪声、降低细节层次
高斯模糊的实现原理这里不做多赘述这里提供2篇文章供参考。
原理参考2D Shader学习——高斯模糊
shader实现参考基于线性采样的高效高斯模糊实现译
参考第二篇文章我们在JavaScript中计算我们高斯卷积核的权重和位移
var SAMPLE_COUNT 15;//高斯曲线
function computeGaussian(n, theta) {return ((1.0 / Math.sqrt(2 * Math.PI * theta)) * Math.exp(-(n * n) / (2 * theta * theta)));
}function calculateBlurValues(sampleWeights, sampleOffsets, dx, dy, blurAmount) {// Create temporary arrays for computing our filter settings.// The first sample always has a zero offset.sampleWeights[0] computeGaussian(0, blurAmount);sampleOffsets[0] 0;sampleOffsets[1] 0;// Maintain a sum of all the weighting values.var totalWeights sampleWeights[0];// Add pairs of additional sample taps, positioned// along a line in both directions from the center.var i, len;for (i 0, len Math.floor(SAMPLE_COUNT / 2); i len; i) {// Store weights for the positive and negative taps.var weight computeGaussian(i 1, blurAmount);sampleWeights[i * 2] weight;sampleWeights[i * 2 1] weight;totalWeights weight * 2;var sampleOffset i * 2 1.5;sampleOffsets[i * 4] dx * sampleOffset;sampleOffsets[i * 4 1] dy * sampleOffset;sampleOffsets[i * 4 2] -dx * sampleOffset;sampleOffsets[i * 4 3] -dy * sampleOffset;}// Normalize the list of sample weightings, so they will always sum to one.for (i 0, len sampleWeights.length; i len; i) {sampleWeights[i] / totalWeights;}
}
在fragment shader中对图像进行卷积模糊注意这里的shader只对水平或垂直一个方向卷积
#define SAMPLE_COUNT 15varying vec2 vUv0;uniform sampler2D uBloomTexture;
uniform vec2 uBlurOffsets[15];
uniform float uBlurWeights[15];void main(void)
{vec4 color vec4(0.0);for (int i 0; i SAMPLE_COUNT; i){color texture2D(uBloomTexture, vUv0 uBlurOffsets[i]) * uBlurWeights[i];}gl_FragColor color;
}
最后我们需要进行2次方向的滤波处理
原理具体参考文章二中如何将高斯滤波器分为水平方向和垂直方向的滤波器的原理
// Pass 2: draw from rendertarget 1 into rendertarget 2垂直方向
calculateBlurValues(this.sampleWeights, this.sampleOffsets, 1.0 / this.targets[1].width, 0, this.blurAmount);
scope.resolve(uBlurWeights[0]).setValue(this.sampleWeights);
scope.resolve(uBlurOffsets[0]).setValue(this.sampleOffsets);
scope.resolve(uBloomTexture).setValue(this.targets[0].colorBuffer);
this.drawQuad(this.targets[1], this.blurShader);// Pass 3: draw from rendertarget 2 back into rendertarget 1水平方向
calculateBlurValues(this.sampleWeights, this.sampleOffsets, 0, 1.0 / this.targets[0].height, this.blurAmount);
scope.resolve(uBlurWeights[0]).setValue(this.sampleWeights);
scope.resolve(uBlurOffsets[0]).setValue(this.sampleOffsets);
scope.resolve(uBloomTexture).setValue(this.targets[1].colorBuffer);
this.drawQuad(this.targets[0], this.blurShader);
3. 混合原图和模糊图
那我们最后的fragment shader就可以这样实现原图模糊图进行混合
varying vec2 vUv0;//bloom 强度
uniform float uBloomEffectIntensity;uniform sampler2D uBaseTexture;
uniform sampler2D uBloomTexture;void main(void)
{vec4 bloom texture2D(uBloomTexture, vUv0) * uBloomEffectIntensity;vec4 base texture2D(uBaseTexture, vUv0);//将原图变暗防止两图叠加后像素溢出1base * (1.0 - clamp(bloom, 0.0, 1.0));//合并原图和模糊图得到最终的bloom效果gl_FragColor base bloom;
}
三在playcanvas编辑器中使用
1. 创建脚本bloom.js
// --------------- POST EFFECT DEFINITION --------------- //
var SAMPLE_COUNT 15;function computeGaussian(n, theta) {return ((1.0 / Math.sqrt(2 * Math.PI * theta)) * Math.exp(-(n * n) / (2 * theta * theta)));
}function calculateBlurValues(sampleWeights, sampleOffsets, dx, dy, blurAmount) {// Look up how many samples our gaussian blur effect supports.// Create temporary arrays for computing our filter settings.// The first sample always has a zero offset.sampleWeights[0] computeGaussian(0, blurAmount);sampleOffsets[0] 0;sampleOffsets[1] 0;// Maintain a sum of all the weighting values.var totalWeights sampleWeights[0];// Add pairs of additional sample taps, positioned// along a line in both directions from the center.var i, len;for (i 0, len Math.floor(SAMPLE_COUNT / 2); i len; i) {// Store weights for the positive and negative taps.var weight computeGaussian(i 1, blurAmount);sampleWeights[i * 2] weight;sampleWeights[i * 2 1] weight;totalWeights weight * 2;// To get the maximum amount of blurring from a limited number of// pixel shader samples, we take advantage of the bilinear filtering// hardware inside the texture fetch unit. If we position our texture// coordinates exactly halfway between two texels, the filtering unit// will average them for us, giving two samples for the price of one.// This allows us to step in units of two texels per sample, rather// than just one at a time. The 1.5 offset kicks things off by// positioning us nicely in between two texels.var sampleOffset i * 2 1.5;// Store texture coordinate offsets for the positive and negative taps.sampleOffsets[i * 4] dx * sampleOffset;sampleOffsets[i * 4 1] dy * sampleOffset;sampleOffsets[i * 4 2] -dx * sampleOffset;sampleOffsets[i * 4 3] -dy * sampleOffset;}// Normalize the list of sample weightings, so they will always sum to one.for (i 0, len sampleWeights.length; i len; i) {sampleWeights[i] / totalWeights;}
}/*** class* name BloomEffect* classdesc Implements the BloomEffect post processing effect.* description Creates new instance of the post effect.* augments PostEffect* param {GraphicsDevice} graphicsDevice - The graphics device of the application.* property {number} bloomThreshold Only pixels brighter then this threshold will be processed. Ranges from 0 to 1.* property {number} blurAmount Controls the amount of blurring.* property {number} bloomIntensity The intensity of the effect.*/
function BloomEffect(graphicsDevice) {pc.PostEffect.call(this, graphicsDevice);// Shadersvar attributes {aPosition: pc.SEMANTIC_POSITION};// Pixel shader extracts the brighter areas of an image.// This is the first step in applying a bloom postprocess.var extractFrag [varying vec2 vUv0;,,uniform sampler2D uBaseTexture;,uniform float uBloomThreshold;,,float luminance(vec4 color),{, return 0.2125 * color[0] 0.7154 * color[1] 0.0721 * color[2]; ,},,void main(void),{,// Look up the original image color. vec4 color texture2D(uBaseTexture, vUv0);,,// Adjust it to keep only values brighter than the specified threshold. float val clamp(luminance(color) - uBloomThreshold, 0.0, 1.0);, gl_FragColor color * val;,}].join(\n);// Pixel shader applies a one dimensional gaussian blur filter.// This is used twice by the bloom postprocess, first to// blur horizontally, and then again to blur vertically.var gaussianBlurFrag [#define SAMPLE_COUNT SAMPLE_COUNT,,varying vec2 vUv0;,,uniform sampler2D uBloomTexture;,uniform vec2 uBlurOffsets[ SAMPLE_COUNT ];,uniform float uBlurWeights[ SAMPLE_COUNT ];,,void main(void),{, vec4 color vec4(0.0);,// Combine a number of weighted image filter taps. for (int i 0; i SAMPLE_COUNT; i), {, color texture2D(uBloomTexture, vUv0 uBlurOffsets[i]) * uBlurWeights[i];, },, gl_FragColor color;,}].join(\n);// Pixel shader combines the bloom image with the original// scene, using tweakable intensity levels.// This is the final step in applying a bloom postprocess.var combineFrag [varying vec2 vUv0;,,uniform float uBloomEffectIntensity;,uniform sampler2D uBaseTexture;,uniform sampler2D uBloomTexture;,,void main(void),{,// Look up the bloom and original base image colors. vec4 bloom texture2D(uBloomTexture, vUv0) * uBloomEffectIntensity;, vec4 base texture2D(uBaseTexture, vUv0);,,// Darken down the base image in areas where there is a lot of bloom,// to prevent things looking excessively burned-out. base * (1.0 - clamp(bloom, 0.0, 1.0));,,// Combine the two images. gl_FragColor base bloom;,}].join(\n);this.extractShader pc.createShaderFromCode(graphicsDevice, pc.PostEffect.quadVertexShader, extractFrag, BloomExtractShader, attributes);this.blurShader pc.createShaderFromCode(graphicsDevice, pc.PostEffect.quadVertexShader, gaussianBlurFrag, BloomBlurShader, attributes);this.combineShader pc.createShaderFromCode(graphicsDevice, pc.PostEffect.quadVertexShader, combineFrag, BloomCombineShader, attributes);this.targets [];// Effect defaultsthis.bloomThreshold 0.25;this.blurAmount 4;this.bloomIntensity 1.25;// Uniformsthis.sampleWeights new Float32Array(SAMPLE_COUNT);this.sampleOffsets new Float32Array(SAMPLE_COUNT * 2);
}BloomEffect.prototype Object.create(pc.PostEffect.prototype);
BloomEffect.prototype.constructor BloomEffect;BloomEffect.prototype._destroy function () {if (this.targets) {var i;for (i 0; i this.targets.length; i) {this.targets[i].destroyTextureBuffers();this.targets[i].destroy();}}this.targets.length 0;
};BloomEffect.prototype._resize function (target) {var width target.colorBuffer.width;var height target.colorBuffer.height;if (width this.width height this.height)return;this.width width;this.height height;this._destroy();// Render targetsvar i;for (i 0; i 2; i) {var colorBuffer new pc.Texture(this.device, {name: Bloom Texture i,format: pc.PIXELFORMAT_RGBA8,width: width 1,height: height 1,mipmaps: false});colorBuffer.minFilter pc.FILTER_LINEAR;colorBuffer.magFilter pc.FILTER_LINEAR;colorBuffer.addressU pc.ADDRESS_CLAMP_TO_EDGE;colorBuffer.addressV pc.ADDRESS_CLAMP_TO_EDGE;colorBuffer.name pe-bloom- i;var bloomTarget new pc.RenderTarget({name: Bloom Render Target i,colorBuffer: colorBuffer,depth: false});this.targets.push(bloomTarget);}
};Object.assign(BloomEffect.prototype, {render: function (inputTarget, outputTarget, rect) {this._resize(inputTarget);var device this.device;var scope device.scope;// Pass 1: draw the scene into rendertarget 1, using a// shader that extracts only the brightest parts of the image.scope.resolve(uBloomThreshold).setValue(this.bloomThreshold);scope.resolve(uBaseTexture).setValue(inputTarget.colorBuffer);this.drawQuad(this.targets[0], this.extractShader);// Pass 2: draw from rendertarget 1 into rendertarget 2,// using a shader to apply a horizontal gaussian blur filter.calculateBlurValues(this.sampleWeights, this.sampleOffsets, 1.0 / this.targets[1].width, 0, this.blurAmount);scope.resolve(uBlurWeights[0]).setValue(this.sampleWeights);scope.resolve(uBlurOffsets[0]).setValue(this.sampleOffsets);scope.resolve(uBloomTexture).setValue(this.targets[0].colorBuffer);this.drawQuad(this.targets[1], this.blurShader);// Pass 3: draw from rendertarget 2 back into rendertarget 1,// using a shader to apply a vertical gaussian blur filter.calculateBlurValues(this.sampleWeights, this.sampleOffsets, 0, 1.0 / this.targets[0].height, this.blurAmount);scope.resolve(uBlurWeights[0]).setValue(this.sampleWeights);scope.resolve(uBlurOffsets[0]).setValue(this.sampleOffsets);scope.resolve(uBloomTexture).setValue(this.targets[1].colorBuffer);this.drawQuad(this.targets[0], this.blurShader);// Pass 4: draw both rendertarget 1 and the original scene// image back into the main backbuffer, using a shader that// combines them to produce the final bloomed result.scope.resolve(uBloomEffectIntensity).setValue(this.bloomIntensity);scope.resolve(uBloomTexture).setValue(this.targets[0].colorBuffer);scope.resolve(uBaseTexture).setValue(inputTarget.colorBuffer);this.drawQuad(outputTarget, this.combineShader, rect);}
});// ----------------- SCRIPT DEFINITION ------------------ //
var Bloom pc.createScript(bloom);Bloom.attributes.add(bloomIntensity, {type: number,default: 1,min: 0,title: Intensity
});Bloom.attributes.add(bloomThreshold, {type: number,default: 0.25,min: 0,max: 1,title: Threshold
});Bloom.attributes.add(blurAmount, {type: number,default: 4,min: 1,title: Blur amount
});Bloom.prototype.initialize function () {this.effect new BloomEffect(this.app.graphicsDevice);this.effect.bloomThreshold this.bloomThreshold;this.effect.blurAmount this.blurAmount;this.effect.bloomIntensity this.bloomIntensity;var queue this.entity.camera.postEffects;queue.addEffect(this.effect);this.on(attr, function (name, value) {this.effect[name] value;}, this);this.on(state, function (enabled) {if (enabled) {queue.addEffect(this.effect);} else {queue.removeEffect(this.effect);}});this.on(destroy, function () {queue.removeEffect(this.effect);this.effect._destroy();});
};
2. 将脚本挂载在相机
