Cocos2dx的Shader由GLProgram、GLProgramState、GLProgramCache、GLProgramStateCache组成。
GLProgram是Cocos2dx对Program的封装,一般提供一些静态方法,被多个节点复用。而GLProgramState是对GLProgram的封装,提供更加便捷的 *** 作接口,内部记录了Uniform和Attribute,可以看作一个动态的对象。GLProgram和GLProgramState可以对比理解类和对象的区别。
它们分别对应的xxCache类顾名思义用来做缓冲的,如Cocos2dx中所有内置Shader的名字,就在GLProgramCache的loadDefaultGLProgram()方法中,将所有内置的Shader都创建了出来并缓存。
下面我们先来分析下源码,看看Cocos2dx对Shader是怎么封装的,它与一般OpenGL编写的Shader脚本不同。
首先是GLProgram的compileShader()方法中,编译Shader前使用了precision关键字来设定数值的精度。总共有低精度lowp、中精度mediump、高精度highp可以选择,可以为浮点数或整数指定精度,精度越高效果越好,但消耗也越大。另外,顶点着色器支持的精度要比片段着色器高,片段着色器的highp精度的支持对于显卡而言,是可选的。
然后,它还会在Shader脚本前定义一系列Uniform变量。这些都是Cocos2dx内置的Uniform,在Shader中可以直接使用。下面是源码剪切:
bool GLProgram::compileShader(gluint* shader,GLenum type,const GLchar* source,const std::string& converteddefines){ Glint status; if (!source) { return false; } const GLchar *sources[] = {#if CC_TARGET_PLATFORM == CC_PLATFORM_WINRT (type == GL_VERTEX_SHADER ? "precision mediump float;\n precision mediump int;\n" : "precision mediump float;\n precision mediump int;\n"),#elif (CC_TARGET_PLATFORM != CC_PLATFORM_WIN32 && CC_TARGET_PLATFORM != CC_PLATFORM_liNUX && CC_TARGET_PLATFORM != CC_PLATFORM_MAC) (type == GL_VERTEX_SHADER ? "precision highp float;\n precision highp int;\n" : "precision mediump float;\n precision mediump int;\n"),#endif COCOS2D_SHADER_UNIFORMS,converteddefines.c_str(),source}; *shader = glCreateShader(type); glShaderSource(*shader,sizeof(sources)/sizeof(*sources),sources,nullptr); glCompileShader(*shader); glGetShaderiv(*shader,GL_COMPILE_STATUS,&status); if (! status) { GLsizei length; glGetShaderiv(*shader,GL_SHADER_SOURCE_LENGTH,&length); GLchar* src = (GLchar *)malloc(sizeof(GLchar) * length); glGetShaderSource(*shader,length,nullptr,src); cclOG("cocos2d: ERROR: Failed to compile shader:\n%s",src); if (type == GL_VERTEX_SHADER) { cclOG("cocos2d: %s",getVertexShaderLog().c_str()); } else { cclOG("cocos2d: %s",getFragmentShaderLog().c_str()); } free(src); return false; } return (status == GL_TRUE);}
static const char * COCOS2D_SHADER_UNIFORMS = "uniform mat4 CC_PMatrix;\n" "uniform mat4 CC_MVMatrix;\n" "uniform mat4 CC_MVPMatrix;\n" "uniform mat3 CC_normalMatrix;\n" "uniform vec4 CC_Time;\n" "uniform vec4 CC_SinTime;\n" "uniform vec4 CC_CosTime;\n" "uniform vec4 CC_Random01;\n" "uniform sampler2D CC_Texture0;\n" "uniform sampler2D CC_Texture1;\n" "uniform sampler2D CC_Texture2;\n" "uniform sampler2D CC_Texture3;\n" "//CC INCLUDES END\n\n";
在初始化GLProgram时,Cocos2dx会自动根据Shader是否使用了相应的Uniform变量来初始化_flags成员变量相对应的属性。在编译Shader时,GLSL的编译器会自动将没有使用到的Uniform移除(用glGetUniformlocation()方法判断,返回-1就是没有使用)。
voID GLProgram::updateUniforms(){ _builtInUniforms[UNIFORM_AMBIENT_color] = glGetUniformlocation(_program,UNIFORM_name_AMBIENT_color); _builtInUniforms[UNIFORM_P_MATRIX] = glGetUniformlocation(_program,UNIFORM_name_P_MATRIX); _builtInUniforms[UNIFORM_MV_MATRIX] = glGetUniformlocation(_program,UNIFORM_name_MV_MATRIX); _builtInUniforms[UNIFORM_MVP_MATRIX] = glGetUniformlocation(_program,UNIFORM_name_MVP_MATRIX); _builtInUniforms[UNIFORM_norMAL_MATRIX] = glGetUniformlocation(_program,UNIFORM_name_norMAL_MATRIX); _builtInUniforms[UNIFORM_TIME] = glGetUniformlocation(_program,UNIFORM_name_TIME); _builtInUniforms[UNIFORM_SIN_TIME] = glGetUniformlocation(_program,UNIFORM_name_SIN_TIME); _builtInUniforms[UNIFORM_COS_TIME] = glGetUniformlocation(_program,UNIFORM_name_COS_TIME); _builtInUniforms[UNIFORM_RANDOM01] = glGetUniformlocation(_program,UNIFORM_name_RANDOM01); _builtInUniforms[UNIFORM_SAMPLER0] = glGetUniformlocation(_program,UNIFORM_name_SAMPLER0); _builtInUniforms[UNIFORM_SAMPLER1] = glGetUniformlocation(_program,UNIFORM_name_SAMPLER1); _builtInUniforms[UNIFORM_SAMPLER2] = glGetUniformlocation(_program,UNIFORM_name_SAMPLER2); _builtInUniforms[UNIFORM_SAMPLER3] = glGetUniformlocation(_program,UNIFORM_name_SAMPLER3); _flags.usesP = _builtInUniforms[UNIFORM_P_MATRIX] != -1; _flags.usesMV = _builtInUniforms[UNIFORM_MV_MATRIX] != -1; _flags.usesMVP = _builtInUniforms[UNIFORM_MVP_MATRIX] != -1; _flags.usesnormal = _builtInUniforms[UNIFORM_norMAL_MATRIX] != -1; _flags.usesTime = ( _builtInUniforms[UNIFORM_TIME] != -1 || _builtInUniforms[UNIFORM_SIN_TIME] != -1 || _builtInUniforms[UNIFORM_COS_TIME] != -1 ); _flags.usesRandom = _builtInUniforms[UNIFORM_RANDOM01] != -1; this->use(); // Since sample most probably won't change,set it to 0,1,2,3 Now. if(_builtInUniforms[UNIFORM_SAMPLER0] != -1) setUniformlocationWith1i(_builtInUniforms[UNIFORM_SAMPLER0],0); if(_builtInUniforms[UNIFORM_SAMPLER1] != -1) setUniformlocationWith1i(_builtInUniforms[UNIFORM_SAMPLER1],1); if(_builtInUniforms[UNIFORM_SAMPLER2] != -1) setUniformlocationWith1i(_builtInUniforms[UNIFORM_SAMPLER2],2); if(_builtInUniforms[UNIFORM_SAMPLER3] != -1) setUniformlocationWith1i(_builtInUniforms[UNIFORM_SAMPLER3],3);}
上面我们分析了Cocos2dx的Shader会内置很多Uniform变量,也知道了这些Uniform变量是否使用了。那么下一个问题,如果使用了,这些Uniform是什么时候被设置的呢?它们的值又是多少呢?
如果是纹理Uniform,在一开始就会被设置为固定的值,上面源码中也可以看到,同时可以使用4个纹理,在渲染的时候,Cocos2dx会将纹理绑定到指定的纹理采样器中,我们在Shader脚本中可以访问这些采样器,而采样器对应的纹理,由Cocos2dx调用OpenGL的glBindTexture()等方法绑定,因此这个Uniform的值不需要我们设置。
而其它的如矩阵、时间、法线、随机数等Uniform,是在运行的时候动态设置的,这些属性是实时变化的,在程序运行时,Cocos2dx会每帧调用setUniformsForBuiltins()自动设置它们。
voID GLProgram::setUniformsForBuiltins(const Mat4 &matrixMV){ const auto& matrixP = _director->getMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION); if (_flags.usesP) setUniformlocationWithmatrix4fv(_builtInUniforms[UNIFORM_P_MATRIX],matrixP.m,1); if (_flags.usesMV) setUniformlocationWithmatrix4fv(_builtInUniforms[UNIFORM_MV_MATRIX],matrixMV.m,1); if (_flags.usesMVP) { Mat4 matrixMVP = matrixP * matrixMV; setUniformlocationWithmatrix4fv(_builtInUniforms[UNIFORM_MVP_MATRIX],matrixMVP.m,1); } if (_flags.usesnormal) { Mat4 mvInverse = matrixMV; mvInverse.m[12] = mvInverse.m[13] = mvInverse.m[14] = 0.0f; mvInverse.inverse(); mvInverse.transpose(); GLfloat normalMat[9]; normalMat[0] = mvInverse.m[0];normalMat[1] = mvInverse.m[1];normalMat[2] = mvInverse.m[2]; normalMat[3] = mvInverse.m[4];normalMat[4] = mvInverse.m[5];normalMat[5] = mvInverse.m[6]; normalMat[6] = mvInverse.m[8];normalMat[7] = mvInverse.m[9];normalMat[8] = mvInverse.m[10]; setUniformlocationWithmatrix3fv(_builtInUniforms[UNIFORM_norMAL_MATRIX],normalMat,1); } if (_flags.usesTime) { // This doesn't give the most accurate global time value. // Cocos2D doesn't store a high precision time value,so this will have to do. // Getting Mach time per frame per shader using time Could be extremely expensive. float time = _director->getTotalFrames() * _director->getAnimationInterval(); setUniformlocationWith4f(_builtInUniforms[GLProgram::UNIFORM_TIME],time/10.0,time,time*2,time*4); setUniformlocationWith4f(_builtInUniforms[GLProgram::UNIFORM_SIN_TIME],time/8.0,time/4.0,time/2.0,sinf(time)); setUniformlocationWith4f(_builtInUniforms[GLProgram::UNIFORM_COS_TIME],cosf(time)); } if (_flags.usesRandom) setUniformlocationWith4f(_builtInUniforms[GLProgram::UNIFORM_RANDOM01],CCRANDOM_0_1(),CCRANDOM_0_1());}
当然,除了以上内置的Uniform外,Cocos2dx还内置了一些Attribute,但这些变量是需要在Shader脚本中手动输入的,主要是颜色、坐标、纹理坐标、法线等常用属性。它们被定义在CCGLProgram.cpp中,在Renderer进行渲染时,会调用glVertexAttribPointer()设置它们。
// Attribute namesconst char* GLProgram::ATTRIBUTE_name_color = "a_color";const char* GLProgram::ATTRIBUTE_name_position = "a_position";const char* GLProgram::ATTRIBUTE_name_TEX_COORD = "a_texCoord";const char* GLProgram::ATTRIBUTE_name_TEX_COORD1 = "a_texCoord1";const char* GLProgram::ATTRIBUTE_name_TEX_COORD2 = "a_texCoord2";const char* GLProgram::ATTRIBUTE_name_TEX_COORD3 = "a_texCoord3";const char* GLProgram::ATTRIBUTE_name_norMAL = "a_normal";const char* GLProgram::ATTRIBUTE_name_BLEND_WEIGHT = "a_blenDWeight";const char* GLProgram::ATTRIBUTE_name_BLEND_INDEX = "a_blendindex";const char* GLProgram::ATTRIBUTE_name_TANGENT = "a_tangent";const char* GLProgram::ATTRIBUTE_name_BInorMAL = "a_binormal";
整个Cocos2dx的Shader不同的规则大体就是这样了,主要是内置了一系列的变量,由引擎自动设置值,我们可以在自己Shader中直接使用。
Cocos2dx中使用Shader示例我们就编写一个常用的灰化Shader来演示下Cocos2dx中使用Shader的流程。
灰化原理:灰白图片的特征就是每个像素的RGB三个分量的值均相等,值越高颜色越白,反之颜色越黑。常用的算法有3种,平均值、最大值和加权平均值。
首先,我们得分别编写顶点Shader和片段Shader:
//顶点Shaderattribute vec4 a_position; //位置(内置)attribute vec2 a_texCoord; //纹理坐标(内置)varying vec2 v_texCoord; //自定义易变变量(写入值)voID main(){ gl_position = CC_PMatrix * a_position; v_texCoord = a_texCoord;}
//片段着色器//使用加权平均值算RGB分量,即给每个分量指定一个比例,指定比例没有写死,通过一个Uniform变量来设置varying vec2 v_texCoord; //接收顶点着色器传递的值(接收值)uniform vec4 u_grayParam; //指定rgb颜色分量的比例voID main(){ vec4 texcolor = texture2D(CC_Texture0,v_texCoord); texcolor.rgb = texcolor.r * u_grayParam.r + texcolor.g * u_grayParam.g + texcolor.b * u_grayParam.b; gl_Fragcolor = texcolor;}
分别命名为gray.vert和gray.frag保存到磁盘。
好,脚本写完了,下面来看看怎么使用:
#include "renderer/CCGLProgramStateCache.h"//置灰接口voID grayNode(Node* node){ //对应xxCache的运用,先成缓存中找,不需要每次都重新创建 GLProgram* program = GLProgramCache::getInstance()->getGLProgram("MyGrayShader"); if(nullptr == program) { //本地磁盘加载shader创建program,还一种字符串的形式效率要高createWithByteArrays() program = GLProgram::createWithfilenames("gray.vert","gray.frag"); //将GLProgram对象缓存到Cache中 GLProgramCache::getInstance()->addGLProgram(program,"MyGrayShader"); } //通过program创建programState,用它来设置上面自定义的Uniform变量的值 GLProgramState* programState = GLProgramState::getorCreateWithGLProgram(program); programState->setUniformVec4("u_grayParam",Vec4(0.2f,0.3f,0.5f,1.0f)); //调用node节点的setGLProgramState,以后此节点渲染就会使用这个Shader了 node->setGLProgramState(programState);}
//使用auto sprite = Sprite::create(xx.png);grayNode(sprite);
至此,Cocos2dx中使用Shader流程就讲完了~ 最后说下,怎么把置灰的图片再还原回去呢?OpenGL是个状态机的运行机制,所以只需要把设置的Shader还原回去重新设置就行了。这里Sprite对象默认的Shader是GLProgram::SHADER_name_position_TEXTRUE_color_NO_MVP,可以通过GLProgramState::getorCreateWithGLProgramname()传入上面字符串常量来获取它的GLProgramState.
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