OSGEarth绘制动态水效果

在OSGEarth上绘制水效果的思路为：

1. 使用OSG::Geometry的方式绘制多边形；

2. 在绘制的多边形上贴一个水的纹理；

3. 对纹理使用shader效果，使之动态展示。

此种方式适用于小范围的不严格的水效果，若需要大范围或者有水底效果的请使用OSGOcean。

代码如下：water.h

class Water : public HandleAdapter
{
public:
    Water(GraphicsView* view);
    ~Water();

protected:
    virtual void slotPickedXYZ(osg::Vec3d pos);
    virtual void slotMoveingXYZ(osg::Vec3d pos);
    virtual void slotRightHandle();

private:
    void drawWater(osg::Vec3d pos = osg::Vec3d());
    osg::Texture2D* creatText2D(const QString& strFile);
    void initShader();

private:
    osg::ref_ptr<osg::Vec3dArray> m_vecPoints;
    osg::Geode* m_pWater;
    char* m_waterFrag;
    char* m_waterVert;
};

实现代码如下：water.cpp

Water::Water(GraphicsView* view)
: HandleAdapter(view)
{
    m_pWater = NULL;
    m_vecPoints = new osg::Vec3dArray;
    m_vecPoints->clear();

    initShader();
}

Water::~Water()
{

}

void Water::slotPickedXYZ(osg::Vec3d pos)
{
    m_vecPoints->push_back(pos);
    if (m_vecPoints->size() <= 2)
    {
        return;
    }

    drawWater();
}

void Water::slotMoveingXYZ(osg::Vec3d pos)
{
    if (m_vecPoints->size() < 2)
    {
        return;
    }

    drawWater(pos);
}

void Water::slotRightHandle()
{
    endHandle();
    m_pWater = nullptr;
}

void Water::drawWater(osg::Vec3d pos /*= osg::Vec3d()*/)
{
    osg::ref_ptr<osg::Vec3dArray> vecPoints = new osg::Vec3dArray;
    vecPoints = m_vecPoints;
    if (pos == osg::Vec3d() && m_vecPoints->size() <= 2)
    {
        return;
    }
    if (pos != osg::Vec3d())
    {
        vecPoints->push_back(pos);
    }
    osg::ref_ptr<osg::Geometry> pWater = new osg::Geometry;
    pWater->setVertexArray(vecPoints);
    pWater->addPrimitiveSet(
        new osg::DrawArrays(osg::PrimitiveSet::TRIANGLE_FAN, 0, vecPoints->size()));

    //纹理
    osg::ref_ptr<osg::Texture2D> pText2D = new osg::Texture2D;
    pText2D->setTextureSize(1024, 1024);
    pText2D->setInternalFormat(GL_RGBA);

    pWater->getOrCreateStateSet()->setTextureAttributeAndModes(0, pText2D);
    pWater->getOrCreateStateSet()->setTextureAttributeAndModes(1,
        creatText2D("E:/GreatMap/project/version/Data/Bmp/shui_5.jpg"));
    pWater->getOrCreateStateSet()->setTextureAttributeAndModes(2,
        creatText2D("E:/GreatMap/project/version/Data/Bmp/water_DUDV.jpg"));
    pWater->getOrCreateStateSet()->setTextureAttributeAndModes(3,
        creatText2D("E:/GreatMap/project/version/Data/Bmp/water_NM.jpg"));

    // shader
    osg::ref_ptr<osg::Shader> pVeter = new osg::Shader(osg::Shader::VERTEX, m_waterVert);
    osg::ref_ptr<osg::Shader> pFrag = new osg::Shader(osg::Shader::FRAGMENT, m_waterFrag);
    osg::ref_ptr<osg::Program> pProgram = new osg::Program;
    pProgram->addShader(pVeter);
    pProgram->addShader(pFrag);
    pWater->getOrCreateStateSet()->addUniform(new osg::Uniform("reflection", 0));
    pWater->getOrCreateStateSet()->addUniform(new osg::Uniform("defaultTex", 1));
    pWater->getOrCreateStateSet()->addUniform(new osg::Uniform("refraction", 2));
    pWater->getOrCreateStateSet()->addUniform(new osg::Uniform("normalTex", 3));
    pWater->getOrCreateStateSet()->setAttributeAndModes(pProgram);

    if (m_pWater == NULL)
    {
        m_pWater = new osg::Geode;
        m_pLayerGroup->addChild(m_pWater);
    }
    m_pWater->addDrawable(pWater);
    m_pWater->setStateSet(pWater->getOrCreateStateSet());
}

osg::Texture2D* Water::creatText2D(const QString& strFile)
{
    if (strFile.isEmpty())
    {
        return NULL;
    }

    osg::ref_ptr<osg::Texture2D> pText2D = new osg::Texture2D;
    pText2D->setImage(osgDB::readImageFile(strFile.toStdString()));
    pText2D->setWrap(osg::Texture2D::WRAP_S, osg::Texture2D::REPEAT);
    pText2D->setWrap(osg::Texture2D::WRAP_T, osg::Texture2D::REPEAT);
    pText2D->setFilter(osg::Texture2D::MIN_FILTER, osg::Texture::LINEAR_MIPMAP_LINEAR);
    pText2D->setFilter(osg::Texture2D::MAG_FILTER, osg::Texture::LINEAR);
    return pText2D.release();
}

shader的内容如下：

void Water::initShader()
{
    m_waterVert = {
        "uniform float osg_FrameTime;\n"
        "varying vec4 projCoords;\n"
        "varying vec3 lightDir, eyeDir;\n"
        "varying vec2 flowCoords, rippleCoords;\n"

        "void main()\n"
        "{\n"
        "   vec3 T = vec3(0.0, 1.0, 0.0);\n"
        "   vec3 N = vec3(0.0, 0.0, 1.0);\n"
        "   vec3 B = vec3(1.0, 0.0, 0.0);\n"
        "   T = normalize(gl_NormalMatrix * T);\n"
        "   B = normalize(gl_NormalMatrix * B);\n"
        "   N = normalize(gl_NormalMatrix * N);\n"

        "   mat3 TBNmat;\n"
        "   TBNmat[0][0] = T[0]; TBNmat[1][0] = T[1]; TBNmat[2][0] = T[2];\n"
        "   TBNmat[0][1] = B[0]; TBNmat[1][1] = B[1]; TBNmat[2][1] = B[2];\n"
        "   TBNmat[0][2] = N[0]; TBNmat[1][2] = N[1]; TBNmat[2][2] = N[2];\n"

        "   vec3 vertexInEye = vec3(gl_ModelViewMatrix * gl_Vertex);\n"
        "   lightDir =  gl_LightSource[0].position.xyz - vertexInEye;\n"
        "   lightDir = normalize(TBNmat * lightDir);\n"
        "   eyeDir = normalize(TBNmat * (-vertexInEye));\n"

        "   vec2 t1 = vec2(osg_FrameTime*0.02, osg_FrameTime*0.02);\n"
        "   vec2 t2 = vec2(osg_FrameTime*0.05, osg_FrameTime*0.05);\n"
        "   flowCoords = gl_MultiTexCoord0.xy + t1/10.0;\n" //* 5.0 + t1
        "   rippleCoords = gl_MultiTexCoord0.xy + t1;\n"   //

        "   gl_TexCoord[0] = gl_MultiTexCoord0;\n"
        "   gl_Position = ftransform();\n"
        "   projCoords = gl_Position;\n"
        "}\n"
    };

    m_waterFrag = {
        "uniform sampler2D defaultTex;\n"
        "uniform sampler2D reflection;\n"
        "uniform sampler2D refraction;\n"
        "uniform sampler2D normalTex;\n"
        "varying vec4 projCoords;\n"
        "varying vec3 lightDir, eyeDir;\n"
        "varying vec2 flowCoords, rippleCoords;\n"

        "void main()\n"
        "{\n"
        "   vec2 rippleEffect = 0.02 * texture2D(refraction, rippleCoords * 0.01).xy;\n"
        "   vec4 N = texture2D(normalTex, flowCoords + rippleEffect);\n"
        "   N = N * 2.0 - vec4(1.0);\n"
        "   N.a = 1.0; N = normalize(N);\n"

        "   vec3 refVec = normalize(reflect(-lightDir, vec3(N) * 0.6));\n"
        "   float refAngle = clamp(dot(eyeDir, refVec), 0.0, 1.0);\n"
        "   vec4 specular = vec4(pow(refAngle, 40.0));\n"

        "   vec2 dist = texture2D(refraction, flowCoords + rippleEffect).xy;\n"
        "   dist = (dist * 2.0 - vec2(1.0)) * 0.1;\n"
        "   vec2 uv = projCoords.xy / projCoords.w;\n"
        "   uv = clamp((uv + 1.0) * 0.5 + dist, 0.0, 1.0);\n"

        "   vec4 base = texture2D(defaultTex, uv);\n"
        "   vec4 refl = texture2D(reflection, uv);\n"
        "   gl_FragColor = mix(base, refl + specular, 0.6);\n"
        "}\n"
    };
}

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