http://blog.sina.com.cn/s/blog_78ea87380101eixi.html

此文实现一个简单地水面倒影效果，通过rtt相机 获取倒影纹理， 水的基本实现方法(参考前一博文：osg通过glsl实现一个平面的水效果(法线贴图))，具体代码如下：

vertex定点着色器:

varying vec3 lightdir;           //切线空间灯光向量;

varying vec3 eyedir;             //切线空间眼点向量;

varying vec4 ambient, diffuse, specular;

attribute vec3 tangent;          //顶点切线;

uniform float time;                       //时间更新;

uniform vec3  lightPos;         //灯光的位置;

void main()

{

vec3 vVertex = vec3(gl_ModelViewMatrix * gl_Vertex);

vec3 L = normalize(lightPos - vVertex);                 //定点到光源向量;

vec3 E = normalize(-vVertex);                                     //定点到眼点向量;

vec3 N = normalize(gl_NormalMatrix * gl_Normal);

vec3 H = normalize(L + E);

//获取漫反射， 镜面反射量;

ambient = vec4(1.0,1.0,1.0,1.0);

diffuse = vec4(1.0,1.0,1.0,1.0);

specular = vec4(1.0,1.0,1.0,1.0);

float _diffuse = max(dot(L, N), 0.0);

if(_diffuse > 0.0)

{

diffuse = diffuse * _diffuse;

float _specular = max(dot(H,N),0.0);

specular = specular * pow(_specular , 64.0);

}

//计算切线空间量;

vec3 T = normalize(vec3(gl_NormalMatrix * tangent));

vec3 B = normalize(cross(N,T));

lightdir.x = dot(L,T);

lightdir.y = dot(L,B);

lightdir.z = dot(L,N);

lightdir = normalize(lightdir);

eyedir.x = dot(E,T);

eyedir.y = dot(E,B);

eyedir.z = dot(E,N);

lightdir = normalize(eyedir);

gl_TexCoord[0] = gl_MultiTexCoord0;

gl_TexCoord[0].x = 1.0 - gl_TexCoord[0].x;

//根据时间获取法线纹理位置;

gl_TexCoord[1].x = gl_TexCoord[0].x + time * 0.05;

gl_TexCoord[1].y = gl_TexCoord[0].y + time * 0.05;

gl_Position  = ftransform();

}

fragment像素着色器：

varying vec3 lightdir;

varying vec3 eyedir;

varying vec4 ambient, diffuse, specular;

uniform sampler2D baseTex;

uniform sampler2D normTex;

void main()

{

         vec3 L = normalize(lightdir);

         vec3 E = normalize(eyedir);

         vec4 _baseColor = texture2D(baseTex, gl_TexCoord[0].xy);

         vec3 _normColor = texture2D(normTex, gl_TexCoord[1].xy).xyz;

         _baseColor = texture2D(baseTex, gl_TexCoord[0].xy + _normColor * 0.05); //调制底面纹理波动;

         _normColor = texture2D(normTex, gl_TexCoord[1].xy + _normColor * 0.02).xyz;

         vec3 N = normalize(_normColor * 2.0 - vec3(1.0));     //将法线转到[-1,1]范围;

         float _diff = max(dot(L,N),0.0);

         float _spec = max(dot(E,N),0.0);

         if(_diff > 0.0)

         {

                 _spec = pow(_spec, 64.0);

         }

gl_FragColor = vec4(ambient.xyz * _baseColor.xyz + diffuse.xyz * _diff * _baseColor.xyz + specular * _spec, 1.0);

}

osg主程序：

osg::ref_ptr createHalfSphere(osg::Image *img, float radius)

{

         osg::ref_ptr geode = new osg::Geode;

         osg::ref_ptr geom = new osg::Geometry;

         //压入顶点;

         osg::ref_ptr veArr = new osg::Vec3Array;

         std::vector> veVertext;

         //纹理坐标;

         osg::ref_ptr texArr = new osg::Vec2Array;

         std::vector> texVertex;

         for(int i=0; i<=90; i+=10)

         {

                 std::vector veTmp;

                 std::vector _texTmp;

                 for(int j=0; j<=360; j += 10)

                 {

                      double x = radius * cos(osg::DegreesToRadians((float)i)) * cos(osg::DegreesToRadians((float)j));

                      double y = radius * cos(osg::DegreesToRadians((float)i)) * sin(osg::DegreesToRadians((float)j));

                          double z = radius * sin(osg::DegreesToRadians((float)i));

                          veTmp.push_back(osg::Vec3(x,y,z));

                          _texTmp.push_back(osg::Vec2((float)j/370.0+0.01,(float)i/100.0+0.01));

                 }

                 veVertext.push_back(veTmp);

                 texVertex.push_back(_texTmp);

         }

         //重新组织点;

         //法线数组;

         osg::ref_ptr norArr = new osg::Vec3Array;

         std::vector>::iterator it = veVertext.begin();

         for(; it != veVertext.end(); )

         {

                 std::vector _tmp = *it;

                 it++;

                 if(it == veVertext.end())

                          break;

                 int count = (*it).size();

                 for(int i=0; i < count;  ++i)

                 {

                          veArr->push_back(_tmp.at(i));

                          veArr->push_back(it->at(i));

                          norArr->push_back(osg::Vec3(0,0,0) - _tmp.at(i));

                          norArr->push_back(osg::Vec3(0,0,0) - it->at(i));

                 }

         }

         geom->setVertexArray(veArr);

         std::vector>::iterator itt = texVertex.begin();

         for(; itt != texVertex.end(); )

         {

                 std::vector _tmp = *itt;

                 itt++;

                 if(itt == texVertex.end())

                          break;

                 int count = (*itt).size();

                 for(int i=0; i

                 {

                          texArr->push_back(_tmp.at(i));

                          texArr->push_back(itt->at(i));

                 }

         }

         geom->setTexCoordArray(0,texArr);

         //法线;

         geom->setNormalArray(norArr);

         geom->setNormalBinding(osg::Geometry::AttributeBinding::BIND_PER_VERTEX);

         geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::TRIANGLE_STRIP,0,veArr->size()));

         geode->addDrawable(geom);

         //纹理;

         osg::ref_ptr tex = new osg::Texture2D;

         if(img->valid())

         {

                 tex->setImage(img);

         }

         tex->setWrap(osg::Texture::WRAP_T, osg::Texture::REPEAT);//列向;

         tex->setWrap(osg::Texture::WRAP_S, osg::Texture::REPEAT);//行向;

         geom->getOrCreateStateSet()->setTextureAttributeAndModes(0,tex,osg::StateAttribute::ON);

         //geode->getOrCreateStateSet()->setAttributeAndModes(new osg::CullFace,osg::StateAttribute::ON);

         return geode;

}

osg::ref_ptr createPlane(int _w, int _h)

{

         osg::ref_ptr geode = new osg::Geode;

         osg::ref_ptr geom = new osg::Geometry;

         geode->addDrawable(geom);

         osg::ref_ptr vArr = new osg::Vec3Array;

         vArr->push_back(osg::Vec3(-_w/2.0,-_h/2.0,-10));

         vArr->push_back(osg::Vec3(-_w/2.0,_h/2.0,-10));

         vArr->push_back(osg::Vec3(_w/2.0,_h/2.0,-10));

         vArr->push_back(osg::Vec3(_w/2.0,-_h/2.0,-10));

         geom->setVertexArray(vArr);

         osg::ref_ptr tArr = new osg::Vec2Array;

         tArr->push_back(osg::Vec2(0.0,0.0));

         tArr->push_back(osg::Vec2(0.0,1.0));

         tArr->push_back(osg::Vec2(1.0,1.0));

         tArr->push_back(osg::Vec2(1.0,0.0));

         geom->setTexCoordArray(0, tArr);

         osg::ref_ptr nArr = new osg::Vec3Array;

         nArr->push_back(osg::Vec3(0.0,0.0,1.0));

         geom->setNormalArray(nArr);

         geom->setNormalBinding(osg::Geometry::BIND_OVERALL);

         geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));

         return geode;

}

osg::ref_ptr createCamera(int _x, int _y, int _w, int _h,

         bool _isTargetImpl = false,

         osg::Vec4f _color = osg::Vec4f(0.3,0.6,0.5,1.0),

         osg::Camera::RenderOrder _renderOrder = osg::Camera::POST_RENDER,

         osg::Camera::ReferenceFrame _referenceFrame = osg::Camera::ABSOLUTE_RF)

{

         osg::ref_ptr _camera = new osg::Camera;

         _camera->setViewport(_x, _y, _w, _h);

         _camera->setAllowEventFocus(false);

         _camera->setClearColor(_color);

         _camera->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

         _camera->setRenderOrder(_renderOrder);

         _camera->setReferenceFrame(_referenceFrame);

         if(_isTargetImpl)

         {

                 _camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);

         }

         //_camera->setProjectionMatrixAsOrtho2D(0,0,_w,_h);

         _camera->setProjectionMatrixAsPerspective(30.0,double(_w)/double(_h),0.01, 999.9);

         _camera->setComputeNearFarMode(osg::CullSettings::DO_NOT_COMPUTE_NEAR_FAR);

         return _camera;

}

int main(int argc, char *argv[])

{

         osg::ref_ptr _root = new osg::Group;

         _root->addChild(osgDB::readNodeFile("cow.osg"));

    osg::ref_ptr _skybox = createHalfSphere(osgDB::readImageFile("../images/01.jpg"),1000.0);

         osg::ref_ptr _waterPanle  = createPlane(1200,1200);

         osg::ref_ptr _ceep = osgDB::readNodeFile("ceep.ive");

         osg::ref_ptr _mceep = new osg::MatrixTransform;

         _mceep->addChild(_ceep);

         _mceep->setMatrix(osg::Matrix::translate(500.0, 500.0, 0.0));

osg::ref_ptr _rttCam = createCamera(0,0,600,400,false, osg::Vec4f(0.3,0.5,0.8,1.0),osg::Camera::PRE_RENDER,osg::Camera::ABSOLUTE_RF_INHERIT_VIEWPOINT);

         _rttCam->addChild(_skybox);

         _rttCam->addChild(_mceep);

         _root->addChild(_skybox);

         _root->addChild(_waterPanle);

         _root->addChild(_mceep);

         _root->addChild(_rttCam);

         //背景图片;

         osg::ref_ptr baseTex = new osg::Texture2D;

         baseTex->setTextureSize(600,400);

         baseTex->setInternalFormat(GL_RGBA);

         baseTex->setWrap(osg::Texture::WRAP_S, osg::Texture::REPEAT);

         baseTex->setWrap(osg::Texture::WRAP_T, osg::Texture::REPEAT);

         _rttCam->attach(osg::Camera::COLOR_BUFFER, baseTex);

         //法线图;

         osg::ref_ptr normTex = new osg::Texture2D;

         normTex->setImage(osgDB::readImageFile("../images/water.bmp"));

         normTex->setWrap(osg::Texture::WRAP_S, osg::Texture::REPEAT);

         normTex->setWrap(osg::Texture::WRAP_T, osg::Texture::REPEAT);

         _waterPanle->getOrCreateStateSet()->setTextureAttributeAndModes(0, baseTex, 1);

         _waterPanle->getOrCreateStateSet()->setTextureAttributeAndModes(1, normTex, 1);

         osg::ref_ptr program = new osg::Program;

         osg::ref_ptr  vertShader = new osg::Shader(osg::Shader::VERTEX);

         osg::ref_ptr  fragShader = new osg::Shader(osg::Shader::FRAGMENT);

         program->addShader(vertShader);

         program->addShader(fragShader);

         if(!vertShader->loadShaderSourceFromFile("water.vert"))

         {

                 printf("load vertex shader error !\n");

         }

         if(!fragShader->loadShaderSourceFromFile("water.frag"))

         {

                 printf("load fragment shader error !\n");

         }

         _waterPanle->getOrCreateStateSet()->setAttribute(program, 1);

         _waterPanle->getOrCreateStateSet()->addUniform(new osg::Uniform("time", float(0.0)));

         _waterPanle->getOrCreateStateSet()->addUniform(new osg::Uniform("baseTex", 0));

         _waterPanle->getOrCreateStateSet()->addUniform(new osg::Uniform("normTex", 1));

_waterPanle->getOrCreateStateSet()->addUniform(new osg::Uniform("lightPos", osg::Vec3(0.0,0.0,0.0)));//lightPos

         osg::ref_ptr viewer = new osgViewer::Viewer;

         viewer->setSceneData(_root);

         viewer->setCameraManipulator(new osgGA::TrackballManipulator);

         while(!viewer->done())

         {

                 float _time = viewer->getFrameStamp()->getSimulationTime();

                 _waterPanle->getOrCreateStateSet()->getUniform("time")->set(_time);

                 osg::Matrix _mmt = viewer->getCamera()->getViewMatrix();

                 _waterPanle->getOrCreateStateSet()->getUniform("lightPos")->set(_mmt.getTrans());

                 osg::Vec3 _eye, _center, _up;

                 viewer->getCamera()->getViewMatrixAsLookAt(_eye, _center, _up);

                 osg::Vec3 _ttDir = _center - _eye;

                 osg::Vec3 _refEye = osg::Vec3(_eye.x(),_eye.y(),-_eye.z());

                 osg::Vec3 _refCenter = _refEye + osg::Vec3(_ttDir.x(), _ttDir.y(), -_ttDir.z());

                 osg::Vec3 _nnUp = osg::Vec3(_up.x(), _up.y(), -_up.z());

                 _rttCam->setViewMatrixAsLookAt(_refEye,_refCenter,_nnUp);

                 //_rttCam->setViewMatrix(viewer->getCamera()->getViewMatrix());

                 _rttCam->setProjectionMatrix(viewer->getCamera()->getProjectionMatrix());

                 viewer->frame();

         }

         return 0;

}