通过学习 “Cocos2d-X中的后处理效果” 和 “RENDERTEXTURE + BLUR”,我找到了下面的解决方案。
在Cocos2d-X中实现后处理效果的常见方法是使用图层。场景是一层,后处理是另一层,它以场景层作为输入。借助这种技术,后处理可以对渲染后的场景进行操作。
模糊算法是用着色器实现的。在场景上应用模糊效果的常见方法是首先沿着视口的X轴模糊,然后第二次沿着视口的Y轴模糊(参见ShaderLesson5)。这是一个可接受的近似值,可以大大提高性能。
这意味着我们需要在Cocos2d-X中使用2个后处理图层。所以我们需要3层,一层是场景,另外两层是后处理:
m_gameLayer = Layer::create();
this->addChild(m_gameLayer, 0);
m_blurX_PostProcessLayer = PostProcess::create("shader/blur.vert", "shader/blur.frag");
m_blurX_PostProcessLayer->setAnchorPoint(Point::ZERO);
m_blurX_PostProcessLayer->setPosition(Point::ZERO);
this->addChild(m_blurX_PostProcessLayer, 1);
m_blurY_PostProcessLayer = PostProcess::create("shader/blur.vert", "shader/blur.frag");
m_blurY_PostProcessLayer->setAnchorPoint(Point::ZERO);
m_blurY_PostProcessLayer->setPosition(Point::ZERO);
this->addChild(m_blurY_PostProcessLayer, 2);
注意,场景的精灵和资源必须添加到m_gameLayer
中。
在updated
方法中,必须将后处理应用于场景(稍后我将描述如何设置uniforms):
cocos2d::GLProgramState &blurXstate = m_blurX_PostProcessLayer->ProgramState();
blurXstate.setUniformVec2( "u_blurOffset", Vec2( 1.0f/visibleSize.width, 0.0 ) );
blurXstate.setUniformFloat( "u_blurStrength", (float)blurStrength );
m_blurX_PostProcessLayer->draw(m_gameLayer);
cocos2d::GLProgramState &blurYstate = m_blurY_PostProcessLayer->ProgramState();
blurYstate.setUniformVec2( "u_blurOffset", Vec2( 0.0, 1.0f/visibleSize.height ) );
blurYstate.setUniformFloat( "u_blurStrength", (float)blurStrength );
m_blurY_PostProcessLayer->draw(m_blurX_PostProcessLayer);
为了管理后续过程,我实现了一个名为PostProcess
的类,尝试尽可能简单:
PostProcess.hpp
#include <string>
#include "cocos2d.h"
class PostProcess : public cocos2d::Layer
{
private:
PostProcess(void) {}
virtual ~PostProcess() {}
public:
static PostProcess* create(const std::string& vertexShaderFile, const std::string& fragmentShaderFile);
virtual bool init(const std::string& vertexShaderFile, const std::string& fragmentShaderFile);
void draw(cocos2d::Layer* layer);
cocos2d::GLProgram & Program( void ) { return *_program; }
cocos2d::GLProgramState & ProgramState( void ) { return *_progState; }
private:
cocos2d::GLProgram *_program;
cocos2d::GLProgramState *_progState;
cocos2d::RenderTexture *_renderTexture;
cocos2d::Sprite *_sprite;
};
后处理.cpp
#include "PostProcess.hpp"
using namespace cocos2d;
bool PostProcess::init(const std::string& vertexShaderFile, const std::string& fragmentShaderFile)
{
if (!Layer::init()) {
return false;
}
_program = GLProgram::createWithFilenames(vertexShaderFile, fragmentShaderFile);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_COLOR, GLProgram::VERTEX_ATTRIB_POSITION);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_COLOR);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORD);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD1, GLProgram::VERTEX_ATTRIB_TEX_COORD1);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD2, GLProgram::VERTEX_ATTRIB_TEX_COORD2);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD3, GLProgram::VERTEX_ATTRIB_TEX_COORD3);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_NORMAL, GLProgram::VERTEX_ATTRIB_NORMAL);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_BLEND_WEIGHT, GLProgram::VERTEX_ATTRIB_BLEND_WEIGHT);
_program->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_BLEND_INDEX, GLProgram::VERTEX_ATTRIB_BLEND_INDEX);
_program->link();
_progState = GLProgramState::getOrCreateWithGLProgram(_program);
_program->updateUniforms();
auto visibleSize = Director::getInstance()->getVisibleSize();
_renderTexture = RenderTexture::create(visibleSize.width, visibleSize.height);
_renderTexture->retain();
_sprite = Sprite::createWithTexture(_renderTexture->getSprite()->getTexture());
_sprite->setTextureRect(Rect(0, 0, _sprite->getTexture()->getContentSize().width,
_sprite->getTexture()->getContentSize().height));
_sprite->setAnchorPoint(Point::ZERO);
_sprite->setPosition(Point::ZERO);
_sprite->setFlippedY(true);
_sprite->setGLProgram(_program);
_sprite->setGLProgramState(_progState);
this->addChild(_sprite);
return true;
}
void PostProcess::draw(cocos2d::Layer* layer)
{
_renderTexture->beginWithClear(0.0f, 0.0f, 0.0f, 0.0f);
layer->visit();
_renderTexture->end();
}
PostProcess* PostProcess::create(const std::string& vertexShaderFile, const std::string& fragmentShaderFile)
{
auto p = new (std::nothrow) PostProcess();
if (p && p->init(vertexShaderFile, fragmentShaderFile)) {
p->autorelease();
return p;
}
delete p;
return nullptr;
}
着色器需要一个包含模糊算法偏移量的uniform变量 (
u_blurOffset
)。这是第一个模糊通道中两个像素间距离的X轴距离和第二个模糊通道中两个纹理元素间距离的Y轴距离。
模糊效果的强度由uniform变量 (
u_blurStrength
) 设置。其中0.0表示模糊关闭,1.0表示最大模糊程度。最大模糊效果由
MAX_BLUR_WIDHT
的值定义,它定义了在每个方向上查看的纹理元素的范围。因此,这或多或少是模糊半径。如果增加该值,模糊效果将增加,但性能会降低。如果减小该值,则模糊效果将减小,但性能将提高。幸运的是,由于近似的两次实现,性能和
MAX_BLUR_WIDHT
值之间的关系是线性的(而不是二次的)。
我决定避免预先计算高斯权重并将其传递到着色器中(高斯权重将取决于
MAX_BLUR_WIDHT
和
u_blurStrength
)。相反,我使用了一个平滑的
Hermite插值,类似于GLSL函数
smoothstep
:
attribute vec4 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
void main()
{
gl_Position = CC_MVPMatrix * a_position;
v_fragmentColor = a_color;
v_texCoord = a_texCoord;
}
模糊.frag
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
uniform vec2 u_blurOffset;
uniform float u_blurStrength;
#define MAX_BLUR_WIDHT 10
void main()
{
vec4 color = texture2D(CC_Texture0, v_texCoord);
float blurWidth = u_blurStrength * float(MAX_BLUR_WIDHT);
vec4 blurColor = vec4(color.rgb, 1.0);
for (int i = 1; i <= MAX_BLUR_WIDHT; ++ i)
{
if ( float(i) >= blurWidth )
break;
float weight = 1.0 - float(i) / blurWidth;
weight = weight * weight * (3.0 - 2.0 * weight);
vec4 sampleColor1 = texture2D(CC_Texture0, v_texCoord + u_blurOffset * float(i));
vec4 sampleColor2 = texture2D(CC_Texture0, v_texCoord - u_blurOffset * float(i));
blurColor += vec4(sampleColor1.rgb + sampleColor2.rgb, 2.0) * weight;
}
gl_FragColor = vec4(blurColor.rgb / blurColor.w, color.a);
}
完整的C++和GLSL源代码可以在GitHub上找到(实现可以通过bool HelloWorld::m_blurFast = false
激活)。
查看预览:
每个模糊半径单独使用着色器
高性能版本的高斯模糊算法是GPUImage-x介绍的解决方案。在这种实现中,为每个模糊半径创建了单独的模糊着色器。完整的 cocos2d-x 演示实现的源代码可以在GitHub上找到。该实现提供了两个变体,标准实现和优化实现,如链接中所述,可以通过 bool GPUimageBlur::m_optimized
进行设置。该实现为每个半径从0到 int GPUimageBlur::m_maxRadius
生成一个着色器和一个sigma float GPUimageBlur::m_sigma
。
查看预览:
快速限制质量模糊
一个更加强大的解决方案,但明显质量非常低的是使用Optimizing Gaussian blurs on a mobile GPU中介绍的着色器。模糊不是动态的,只能开启或关闭:
update
方法:
cocos2d::GLProgramState &blurPass1state = m_blurPass1_PostProcessLayer->ProgramState();
blurPass1state.setUniformVec2( "u_blurOffset", Vec2( blurStrength/visibleSize.width, blurStrength/visibleSize.height ) );
m_gameLayer->setVisible( true );
m_blurPass1_PostProcessLayer->draw(m_gameLayer);
m_gameLayer->setVisible( false );
cocos2d::GLProgramState &blurPass2state = m_blurPass2_PostProcessLayer->ProgramState();
blurPass2state.setUniformVec2( "u_blurOffset", Vec2( blurStrength/visibleSize.width, -blurStrength/visibleSize.height ) );
m_blurPass1_PostProcessLayer->setVisible( true );
m_blurPass2_PostProcessLayer->draw(m_blurPass1_PostProcessLayer);
m_blurPass1_PostProcessLayer->setVisible( false );
顶点着色器:
attribute vec4 a_position;
attribute vec2 a_texCoord;
varying vec2 blurCoordinates[5];
uniform vec2 u_blurOffset;
void main()
{
gl_Position = CC_MVPMatrix * a_position;
blurCoordinates[0] = a_texCoord.xy;
blurCoordinates[1] = a_texCoord.xy + u_blurOffset * 1.407333;
blurCoordinates[2] = a_texCoord.xy - u_blurOffset * 1.407333;
blurCoordinates[3] = a_texCoord.xy + u_blurOffset * 3.294215;
blurCoordinates[4] = a_texCoord.xy - u_blurOffset * 3.294215;
}
片段着色器
varying vec2 blurCoordinates[5];
uniform float u_blurStrength;
void main()
{
vec4 sum = vec4(0.0);
sum += texture2D(CC_Texture0, blurCoordinates[0]) * 0.204164;
sum += texture2D(CC_Texture0, blurCoordinates[1]) * 0.304005;
sum += texture2D(CC_Texture0, blurCoordinates[2]) * 0.304005;
sum += texture2D(CC_Texture0, blurCoordinates[3]) * 0.093913;
sum += texture2D(CC_Texture0, blurCoordinates[4]) * 0.093913;
gl_FragColor = sum;
}
查看预览:
完整的C++和GLSL源代码可以在GitHub上找到(实现可以通过bool HelloWorld::m_blurFast
进行切换)。
两层(帧缓冲区)逐步解决方案
这种解决方案的想法是对场景进行平滑、逐步、高质量的模糊处理。为此,需要一种弱但快速且高质量的模糊算法。模糊的精灵不会被删除,它将被存储到游戏引擎的下一次刷新中,并用作下一次模糊步骤的源。这意味着弱模糊的精灵再次变得模糊,因此比上一个更加模糊。这是一个渐进的过程,最终形成一个强大而准确的模糊精灵。
为了设置此过程,需要3个图层,即游戏图层和2个模糊图层(偶数和奇数)。
m_gameLayer = Layer::create();
m_gameLayer->setVisible( false );
this->addChild(m_gameLayer, 0);
// blur layer even
m_blur_PostProcessLayerEven = PostProcess::create("shader/blur_fast2.vert", "shader/blur_fast2.frag");
m_blur_PostProcessLayerEven->setVisible( false );
m_blur_PostProcessLayerEven->setAnchorPoint(Point::ZERO);
m_blur_PostProcessLayerEven->setPosition(Point::ZERO);
this->addChild(m_blur_PostProcessLayerEven, 1);
// blur layer odd
m_blur_PostProcessLayerOdd = PostProcess::create("shader/blur_fast2.vert", "shader/blur_fast2.frag");
m_blur_PostProcessLayerOdd->setVisible( false );
m_blur_PostProcessLayerOdd->setAnchorPoint(Point::ZERO);
m_blur_PostProcessLayerOdd->setPosition(Point::ZERO);
this->addChild(m_blur_PostProcessLayerOdd, 1);
注意,最初所有3个图层都是不可见的。
在update方法中,一个图层被设置为可见状态。如果没有模糊,则游戏层是可见的。一旦开始模糊,游戏层将使用模糊着色器渲染到偶数层,游戏层变得不可见,而偶数层变得可见。在下一个循环中,偶数层将使用模糊着色器渲染到奇数层,偶数层变得不可见,而奇数层变得可见。这个过程会继续进行,直到模糊停止。同时,场景变得越来越模糊,质量高。
如果需要再次显示原始场景,则必须将游戏层设置为可见状态,并将偶数和奇数层设置为不可见状态。
update
方法:
bool even = (m_blurTick % 2) == 0;
if ( m_blur )
{
cocos2d::GLProgramState &blurFaststate1 = m_blur_PostProcessLayerEven->ProgramState();
blurFaststate1.setUniformVec2( "u_texelOffset", Vec2( 1.0f/visibleSize.width, 1.0f/visibleSize.height ) );
cocos2d::GLProgramState &blurFaststate2 = m_blur_PostProcessLayerOdd->ProgramState();
blurFaststate2.setUniformVec2( "u_texelOffset", Vec2( -1.0f/visibleSize.width, -1.0f/visibleSize.height ) );
if ( m_blurTick == 0 )
{
m_gameLayer->setVisible( true );
m_blur_PostProcessLayerEven->draw(m_gameLayer);
}
else if ( even )
{
m_blur_PostProcessLayerEven->draw(m_blur_PostProcessLayerOdd);
}
else
{
m_blur_PostProcessLayerOdd->draw(m_blur_PostProcessLayerEven);
}
++m_blurTick;
}
else
m_blurTick = 0;
m_gameLayer->setVisible( !m_blur );
m_blur_PostProcessLayerEven->setVisible( m_blur && even );
m_blur_PostProcessLayerOdd->setVisible( m_blur && !even );
这个着色器是一个简单而精确的3*3模糊着色器:
顶点着色器:
attribute vec4 a_position
attribute vec2 a_texCoord
varying vec2 blurCoordinates[9]
uniform vec2 u_texelOffset
void main()
{
gl_Position = CC_MVPMatrix * a_position
blurCoordinates[0] = a_texCoord.st + vec2( 0.0, 0.0) * u_texelOffset.st
blurCoordinates[1] = a_texCoord.st + vec2(+1.0, 0.0) * u_texelOffset.st
blurCoordinates[2] = a_texCoord.st + vec2(-1.0, 0.0) * u_texelOffset.st
blurCoordinates[3] = a_texCoord.st + vec2( 0.0, +1.0) * u_texelOffset.st
blurCoordinates[4] = a_texCoord.st + vec2( 0.0, -1.0) * u_texelOffset.st
blurCoordinates[5] = a_texCoord.st + vec2(-1.0, -1.0) * u_texelOffset.st
blurCoordinates[6] = a_texCoord.st + vec2(+1.0, -1.0) * u_texelOffset.st
blurCoordinates[7] = a_texCoord.st + vec2(-1.0, +1.0) * u_texelOffset.st
blurCoordinates[8] = a_texCoord.st + vec2(+1.0, +1.0) * u_texelOffset.st
}
片段着色器:
varying vec2 blurCoordinates[9];
void main()
{
vec4 sum = vec4(0.0);
sum += texture2D(CC_Texture0, blurCoordinates[0]) * 4.0;
sum += texture2D(CC_Texture0, blurCoordinates[1]) * 2.0;
sum += texture2D(CC_Texture0, blurCoordinates[2]) * 2.0;
sum += texture2D(CC_Texture0, blurCoordinates[3]) * 2.0;
sum += texture2D(CC_Texture0, blurCoordinates[4]) * 2.0;
sum += texture2D(CC_Texture0, blurCoordinates[5]) * 1.0;
sum += texture2D(CC_Texture0, blurCoordinates[6]) * 1.0;
sum += texture2D(CC_Texture0, blurCoordinates[7]) * 1.0;
sum += texture2D(CC_Texture0, blurCoordinates[8]) * 1.0;
sum /= 16.0;
gl_FragColor = sum;
}
C++和GLSL源代码的完整版本可以在GitHub上找到。
预览: