osg.DrawElementsIndirectUByte

使用间接数组进行渲染的无符号字节索引绘制元素。

说明

osg.DrawElementsIndirectUByte 是OpenSceneGraph 中的一个类，用于使用间接索引数组来进行绘制。

绘制元素使用一个固定的基本类型，无符号字节，长度为1个字节。

继承

osg::DrawElementsUByte -> osg::PrimitiveSet -> osg::Object -> osg::Referenced -> osg::Drawable -> osg::Geode -> osg::Group -> osg::Node -> osg::Object -> osg::Referenced

头文件

#include <osg/DrawElementsIndirectUByte>

类定义

class DrawElementsIndirectUByte : public DrawElementsUByte

公共成员函数

源代码

class DrawElementsIndirectUByte : public DrawElementsUByte
{
public:

    struct Command
    {
        GLuint count;       // number of indexs to be rendered
        GLuint instanceCount;   // number of instances to be rendered
        GLuint firstIndex;  // base index into the element buffer
        GLuint baseVertex;  // offsets added to vertex index
        GLuint baseInstance;    // instance id offset
    };

    DrawElementsIndirectUByte(const GLenum mode, const GLenum type = GL_UNSIGNED_BYTE);
    DrawElementsIndirectUByte(const DrawElementsIndirectUByte& rhs, const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY);

    META_Drawable(osg, DrawElementsIndirectUByte, OSG_EXPORT);

    virtual void draw(osg::State& state, bool useVertexBufferObjects) const;

    void setDrawElementsIndirectBufferObject(BufferObject* drawElementsIndirectBufferObject);
    const BufferObject* getDrawElementsIndirectBufferObject() const;
    BufferObject* getDrawElementsIndirectBufferObject();

    void setDrawElementsIndirectBufferOffset(const GLuint offset) { _indirectByteOffset = offset; }
    GLuint getDrawElementsIndirectOffset() const { return _indirectByteOffset; }
    GLsizei getDrawElementsIndirectStride() const { return _stride; }
    void setInstanceCount(GLuint instanceCount) { _instanceCount = instanceCount; }
    GLuint getInstanceCount() const { return _instanceCount; }
    void setBaseInstance(GLuint baseInstance) { _baseInstance = baseInstance; }
    GLuint getBaseInstance() const { return _baseInstance; }
    void setDrawElementsIndirect(const osg::DrawElementsIndirectUByte::Command& command);
    void setDrawElementsIndirect(GLenum mode, GLenum type, GLsizei count, GLuint byteOffset, GLuint instanceCount, GLuint baseInstance);
    const osg::DrawElementsIndirectUByte::Command& getDrawElementsIndirect() const;
    osg::DrawElementsIndirectUByte::Command& getDrawElementsIndirect();

    DrawElementsUByte* getDrawElements() const { return _drawElements.get(); }

protected:
    virtual ~DrawElementsIndirectUByte() {}

    osg::ref_ptr<DrawElementsUByte>   _drawElements;
    GLuint                            _indirectByteOffset;
    GLsizei                           _stride;
    GLuint                            _instanceCount;
    GLuint                            _baseInstance;

    bool                              _locked;
    osg::DrawElementsIndirectUByte::Command _command;
};

示例

// 创建一个 DrawElementsIndirectUByte 对象
osg::ref_ptr<osg::DrawElementsIndirectUByte> drawElementsIndirectUByte = new osg::DrawElementsIndirectUByte(GL_TRIANGLES, GL_UNSIGNED_BYTE);

// 创建数据
GLubyte indices[] = { 0, 1, 2, 3, 4, 5 };
unsigned int numIndices = sizeof(indices) / sizeof(GLubyte);
osg::ref_ptr<osg::ByteArray> indexArray = new osg::ByteArray(reinterpret_cast<char*>(indices), sizeof(indices));

osg::ref_ptr<osg::BufferObject> indexBufferObject = new osg::BufferObject;
indexBufferObject->setUsage(osg::BufferObject::STATIC_DRAW);
indexBufferObject->setTarget(osg::BufferObject::ELEMENT_ARRAY_BUFFER);
indexBufferObject->setDataVariance(osg::Object::STATIC);
indexBufferObject->setData(indexArray);

osg::DrawElementsIndirectUByte::Command command;
command.count = numIndices;
command.instanceCount = 1;
command.firstIndex = 0;
command.baseVertex = 0;
command.baseInstance = 0;
drawElementsIndirectUByte->setDrawElementsIndirect(command);
drawElementsIndirectUByte->setDrawElements(indexArray->getArray(), osg::PrimitiveSet::TRIANGLES);

DrawElements* drawElements = drawElementsIndirectUByte->getDrawElements();
if (drawElements)
{
    // ...
}

参考文献

• OpenSceneGraph 3.6.3 Documentation - osg::DrawElementsIndirectUByte Class Reference
• OpenSceneGraph 3.6.3 Documentation - osg::DrawElementsUByte Class Reference