osg shader 例子

以下是一个简单的osg shader的例子，它使用了相对复杂的光照和纹理映射，用于渲染一个纹理贴图的模型：

osg::ref_ptr<osg::Shader> vertexShader = new osg::Shader(osg::Shader::VERTEX, R"(
    #version 330

    in vec3 vertex;
    in vec3 normal;
    in vec2 texCoord;

    uniform mat4 modelViewMatrix;
    uniform mat4 projectionMatrix;
    uniform mat4 normalMatrix;

    out vec3 normalInterp;
    out vec2 texCoordInterp;
    out vec3 fragPos;

    void main()
    {
        normalInterp = vec3(normalMatrix * vec4(normal, 0.0));
        texCoordInterp = texCoord;
        fragPos = vec3(modelViewMatrix * vec4(vertex, 1.0));
        gl_Position = projectionMatrix * modelViewMatrix * vec4(vertex, 1.0);
    }
)");

osg::ref_ptr<osg::Shader> fragmentShader = new osg::Shader(osg::Shader::FRAGMENT, R"(
    #version 330

    in vec3 normalInterp;
    in vec2 texCoordInterp;
    in vec3 fragPos;

    uniform sampler2D tex;
    uniform vec3 lightPos;
    uniform vec3 lightColor;
    uniform vec3 objectColor;
    uniform float shininess;

    out vec4 fragColor;

    void main()
    {
        vec3 ambient = 0.1 * objectColor;
        vec3 norm = normalize(normalInterp);
        vec3 lightDir = normalize(lightPos - fragPos);
        float diff = max(dot(norm, lightDir), 0.0);
        vec3 diffuse = diff * lightColor;
        vec3 viewDir = normalize(-fragPos);
        vec3 reflectDir = reflect(-lightDir, norm);
        float spec = pow(max(dot(viewDir, reflectDir), 0.0), shininess);
        vec3 specular = spec * lightColor;
        vec4 texColor = texture(tex, texCoordInterp);
        fragColor = vec4((ambient + diffuse + specular) * texColor.rgb, texColor.a);
    }
)");

osg::ref_ptr<osg::Program> program = new osg::Program;
program->addShader(vertexShader.get());
program->addShader(fragmentShader.get());

osg::ref_ptr<osg::StateSet> stateSet = new osg::StateSet;
stateSet->setAttributeAndModes(program.get(), osg::StateAttribute::ON);

osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D;
texture->setImage(osgDB::readImageFile("texture.png"));
stateSet->setTextureAttributeAndModes(0, texture.get(), osg::StateAttribute::ON);

osg::ref_ptr<osg::Node> model = osgDB::readNodeFile("model.obj");
model->setStateSet(stateSet.get());

osgViewer::Viewer viewer;
viewer.setSceneData(model.get());
viewer.run();

这段代码使用了OpenGL的着色器语言(GLSL)来定义顶点着色器和片段着色器，并创建了一个OpenGL程序(Program)对象，将两个着色器链接在一起。然后创建了一个状态集(StateSet)对象，并将程序和纹理对象(texture)绑定到状态集中。最后将状态集设置到模型上，用于渲染整个场景。