[转]Ogre:Hardwarebuffer

 

[转]Ogre:Hardwarebuffer

关键字：

Ogre中的硬件缓存是指在显卡上的存储，这和在内存上的存储一样是可以访问的。有三种硬件缓存:HardwareVertexBuffer(顶点缓存，存储顶点的各种数据）、HardwareIndexBuffer(索引缓存,存储一个mesh的面片的顶点索引）,HardwarePixelBuffer(纹理缓存,存储某个纹理贴图的数据）。这些数据在程序运行时都在显卡的存储上，然而你可以去读和写这些数据，来操控程序中物体的形状、纹理等。这个用处是非常大的。

1、最上面的hardwarevertexbuffer 读写：如果mesh使用的所有子mesh共享buffer的形式，则用mesh的sharedvertexdata，否则用submesh的vertexdata来得到vertexdata结构，vertexdata封装了对该mesh的顶点缓存数据的访问方式，但是却不直接包含这些顶点缓存数据。vertexdata中的vettexbufferbinding可以知道当前的vertexdata对应了确切的硬件上的哪块buffer，可以通过vettexbufferbinding的getBuffer确切的得到该顶点缓存，而vertexdata中的vertexdeclaration则是一个对他对应的buffer进行各种访问的接口，里面有访问的格式等。如果要开始操纵这个buffer，需要将getbuffer得到的hardwarevertexbuffer调用lock，然后将这片缓存上锁，这个lock返回了一个void指针，指向的就是缓存数据。拿着这个指针就可以读取改写等

创建：使用hardwarebuffermanager的create来创建，创建后利用hardwarevertexbuffer的write写入数据

2.中间的hardwareindexbuffer 读写：直接使用submesh的indexdata来得到一个indexdata结构，再调用它的hardwareindexbuffer的来得到这个顶点缓存，童年顶点缓存一样再调用lock来进行读写操作创建：同顶点缓存

3最下面的hardwarepixelbuffer

读写：从texture中可以直接得到这个hardwarepixelbuffer，然后对它lock后就可以得到一个pixelbox的数据，pixebox封装了所有纹理数据及其各种属性信息

创建：texture是由texturemanager创建的

下面是一些具体的使用硬件缓存的例子

读取顶点和索引缓存

Ogre::MeshPtr meshPtr=mainEntity->getMesh(); //假设这里使用的是share的形式 Ogre::VertexData* vertex_data=meshPtr->sharedVertexData;

//得到位置数据的信息 const Ogre::VertexElement* posElem =vertex_data->vertexDeclaration->findElementBySemantic(Ogre::VES_POSITION);

//得到纹理坐标数据的信息 const Ogre::VertexElement*texcoElem=vertex_data->vertexDeclaration->findElementBySemantic(Ogre::VES_TEXTURE_COORDINATES);

//得到位置和纹理的缓存

Ogre::HardwareVertexBufferSharedPtr posBuf=vertex_data->vertexBufferBinding->getBuffer(posElem->getSource()); Ogre::HardwareVertexBufferSharedPtr texcoBuf=vertex_data->vertexBufferBinding->getBuffer(texcoElem->getSource());

//顶点位置缓存的lock，读取 unsigned char* vertexPos =static_cast<unsignedchar*>(posBuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY));

//将第一个点的位置读出 float* pReal;

//这个函数的作用是将当前vertexPos指向的数据用其他型（这里是float*）的指针指向，这样读出来的数据就是float型的了，或者用float型的数据进行写入

posElem->baseVertexPointerToElement(vertexPos, &pReal);

Ogre::Vector3 pt(pReal[0], pReal[1], pReal[2]);

//访问之后要上锁 posBuf->unlock();
//读取索引信息 Ogre::SubMesh* submesh = meshPtr->getSubMesh( i );

//得到这个submesh的indexdata Ogre::IndexData* index_data = submesh->indexData; int numTris = index_data->indexCount / 3;

//得到indexbuffer Ogre::HardwareIndexBufferSharedPtr ibuf = index_data->indexBuffer; bool use32bitindexes = (ibuf->getType() ==Ogre::HardwareIndexBuffer::IT_32BIT);

//得到具体的索引缓存数据 unsigned long* pLong = static_cast<unsignedlong*>(ibuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY)); unsigned short* pShort = reinterpret_cast<unsigned short*>(pLong);

… … ibuf->unlock();

访问纹理缓存

Ogre::HardwarePixelBufferSharedPtrcrossPixbufferPtr=texture.getPointer()->getBuffer(0,0);

crossPixbufferPtr->lock(Ogre::HardwareBuffer::HBL_NORMAL);

Ogre::PixelBox pb=crossPixbufferPtr->getCurrentLock();

int height = pb.getHeight();

int width = pb.getWidth();

int pitch = pb.rowPitch;

// Skip between rows of image uint32* data=static_cast<uint32*>(pb.data);

……操纵data…… crossPixbufferPtr->unlock();

创建顶点缓存和索引缓存，进而根据其创建一个自定义的mesh

void createColourCube()

{

/// Create the mesh via the MeshManager Ogre::MeshPtr msh =MeshManager::getSingleton().createManual("ColourCube","General");

/// Create one submesh SubMesh* sub = msh->createSubMesh();

const float sqrt13 = 0.577350269f;

/* sqrt(1/3) */

/// Define the vertices (8 vertices, each consisting of 2 groups of 3 floats const size_t nVertices = 8;

const size_t vbufCount = 3*2*nVertices;

float vertices[vbufCount] = { -100.0,100.0,-100.0, //0 position -sqrt13,sqrt13,-sqrt13,

//0 normal 100.0,100.0,-100.0,

//1 position sqrt13,sqrt13,-sqrt13,

//1 normal 100.0,-100.0,-100.0,

//2 position sqrt13,-sqrt13,-sqrt13,

//2 normal -100.0,-100.0,-100.0,

//3 position -sqrt13,-sqrt13,-sqrt13,

//3 normal -100.0,100.0,100.0,

//4 position -sqrt13,sqrt13,sqrt13,

//4 normal 100.0,100.0,100.0,

//5 position sqrt13,sqrt13,sqrt13,

//5 normal 100.0,-100.0,100.0,

//6 position sqrt13,-sqrt13,sqrt13,

//6 normal -100.0,-100.0,100.0,

//7 position -sqrt13,-sqrt13,sqrt13,

//7 normal };

RenderSystem* rs = Root::getSingleton().getRenderSystem();

RGBA colours[nVertices]; RGBA *pColour = colours;

// Use render system to convert colour value since colour packing varies rs->convertColourValue(ColourValue(1.0,0.0,0.0), pColour++);

//0 colour rs->convertColourValue(ColourValue(1.0,1.0,0.0), pColour++);

//1 colour rs->convertColourValue(ColourValue(0.0,1.0,0.0), pColour++);

//2 colour rs->convertColourValue(ColourValue(0.0,0.0,0.0), pColour++);

//3 colour rs->convertColourValue(ColourValue(1.0,0.0,1.0), pColour++);

//4 colour rs->convertColourValue(ColourValue(1.0,1.0,1.0), pColour++);

//5 colour rs->convertColourValue(ColourValue(0.0,1.0,1.0), pColour++);

//6 colour rs->convertColourValue(ColourValue(0.0,0.0,1.0), pColour++);

//7 colour

/// Define 12 triangles (two triangles per cube face) ///

The values in this table refer to vertices in the above table

const size_t ibufCount = 36;

unsigned short faces[ibufCount] = { 0,2,3, 0,1,2, 1,6,2, 1,5,6, 4,6,5, 4,7,6, 0,7,4, 0,3,7, 0,5,1, 0,4,5, 2,7,3, 2,6,7 };

/// Create vertex data structure for 8 vertices shared between submeshes

msh->sharedVertexData = new VertexData();

msh->sharedVertexData->vertexCount = nVertices; /

// Create declaration (memory format) of vertex data

VertexDeclaration* decl = msh->sharedVertexData->vertexDeclaration;

size_t offset = 0;

// 1st buffer

decl->addElement(0, offset, VET_FLOAT3, VES_POSITION);

offset += VertexElement::getTypeSize(VET_FLOAT3);

decl->addElement(0, offset, VET_FLOAT3, VES_NORMAL);

offset += VertexElement::getTypeSize(VET_FLOAT3);

/// Allocate vertex buffer of the requested number of vertices (vertexCount)

/// and bytes per vertex (offset)

HardwareVertexBufferSharedPtr vbuf = HardwareBufferManager::getSingleton().createVertexBuffer( offset, msh->sharedVertexData->vertexCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY);

/// Upload the vertex data to the card

vbuf->writeData(0, vbuf->getSizeInBytes(), vertices, true);

/// Set vertex buffer binding so buffer 0 is bound to our vertex buffer

VertexBufferBinding* bind = msh->sharedVertexData->vertexBufferBinding;

bind->setBinding(0, vbuf);

// 2nd buffer

offset = 0;

decl->addElement(1, offset, VET_COLOUR, VES_DIFFUSE);

offset += VertexElement::getTypeSize(VET_COLOUR);

/// Allocate vertex buffer of the requested number of vertices (vertexCount)

/// and bytes per vertex (offset)

vbuf = HardwareBufferManager::getSingleton().createVertexBuffer( offset, msh->sharedVertexData->vertexCount,HardwareBuffer::HBU_STATIC_WRITE_ONLY);

/// Upload the vertex data to the card

vbuf->writeData(0, vbuf->getSizeInBytes(), colours, true);

/// Set vertex buffer binding so buffer 1 is bound to our colour buffer

bind->setBinding(1, vbuf);

/// Allocate index buffer of the requested number of vertices (ibufCount)

HardwareIndexBufferSharedPtr ibuf = HardwareBufferManager::getSingleton(). createIndexBuffer( HardwareIndexBuffer::IT_16BIT, ibufCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY);

/// Upload the index data to the card

ibuf->writeData(0, ibuf->getSizeInBytes(), faces, true);

/// Set parameters of the submesh

sub->useSharedVertices = true;

sub->indexData->indexBuffer = ibuf;

sub->indexData->indexCount = ibufCount;

sub->indexData->indexStart = 0; 

// Set bounding information (for culling)

msh->_setBounds(AxisAlignedBox(-100,-100,-100,100,100,100));

msh->_setBoundingSphereRadius(Math::Sqrt(3*100*100));

/// Notify -Mesh object that it has been loaded

msh->load();

}

然后可以从mesh直接创建entity放在场景中

Entity*thisEntity =sceneManager->createEntity("cc", "ColourCube");