Create & apply dynamic texutre（创建并使用动态创建的纹理）

这个帖子：http://www.ogre3d.org/wiki/index.php/Creating_dynamic_textures

里面讲解了如何创建并使用动态创建的纹理。使用该方法，创建并使用双通道的DDS纹理。具体方法如下：

1.   创建动态纹理：

#include "OgreHardwarePixelBuffer.h"
// Create the texture
TexturePtr texture = TextureManager::getSingleton().createManual(
    "DynamicTexture", // name
    ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME,
    TEX_TYPE_2D,      // type
    256, 256,         // width & height
    0,                // number of mipmaps
    PF_FLOAT32_GR,    // pixel format  （双通道DDS浮点纹理）
    TU_DEFAULT);      // usage; should be TU_DYNAMIC_WRITE_ONLY_DISCARDABLE for
                      // textures updated very often (e.g. each frame)

// Get the pixel buffer
HardwarePixelBufferSharedPtr pixelBuffer = texture->getBuffer();

// Lock the pixel buffer and get a pixel box
pixelBuffer->lock(HardwareBuffer::HBL_NORMAL); // for best performance use HBL_DISCARD!
const PixelBox& pixelBox = pixelBuffer->getCurrentLock();

float* pDest = static_cast<float*>(pixelBox.data);

// Fill in some pixel data. This will give a semi-transparent blue,
// but this is of course dependent on the chosen pixel format.
for (size_t j = 0; j < 256; j++)
    for(size_t i = 0; i < 256; i++)
    {
        *pDest++ = *(gChannel++);  // gChannel:G通道数据数组指针
         *pDest++ = *(rChannel++);  // rChannel:R通道数据数组指针
    }

// Unlock the pixel buffer
pixelBuffer->unlock();

2.   保存动态创建的DDS纹理（Failed！）：

创建完纹理后想用：http://www.ogre3d.org/wiki/index.php/Saving_dynamic_textures

中的方法保存DDS纹理，以查看创建是否正确。代码如下：

void SaveImage(TexturePtr TextureToSave, String filename)
{
    HardwarePixelBufferSharedPtr readbuffer;
    readbuffer = TextureToSave->getBuffer(0, 0);
    readbuffer->lock(HardwareBuffer::HBL_NORMAL );
    const PixelBox &readrefpb = readbuffer->getCurrentLock();	
    uchar *readrefdata = static_cast<uchar*>(readrefpb.data);		

    Image img;
    img = img.loadDynamicImage (readrefdata, TextureToSave->getWidth(),
        TextureToSave->getHeight(), TextureToSave->getFormat());	
    img.save(filename);   // 此处抛出异常：DDS encoding not supported！
    
    readbuffer->unlock();
}

但是，程序执行到img.save(filename)的时候出现异常，提示“不支持DDS编码”。Ogre Forum上面搜到这个贴：

https://www.ogre3d.org/forums/viewtopic.php?f=5&t=38606&start=0 里面有人说：

“Ogre's DDS codec does not support encoding DDS, only decoding.”

查看ogreddscodec.cpp中的异常抛出函数确实是这样的：

    void DDSCodec::codeToFile(MemoryDataStreamPtr& input, 
        const String& outFileName, Codec::CodecDataPtr& pData) const
    {
		OGRE_EXCEPT(Exception::ERR_NOT_IMPLEMENTED,
			"DDS encoding not supported",
			"DDSCodec::codeToFile" ) ;
    }

3.   使用动态纹理：

使用上面创建的动态纹理：

MaterialPtr material = MaterialManager::getSingleton().getByName("Test");
material.getPointer()->getTechnique(0)->getPass(0)->getTextureUnitState("DynamicTextureTU")->setTextureName("DynamicTextureTU");

材质Test的定义：

material Test
{
	technique
	{
		pass
		{
			lighting off
			scene_blend alpha_blend
			depth_write off			
            texture_unit DynamicTextureTU
			{ // blank
			}

		}
	}
	
}

PS:真正意义的处女贴！