整合OGRE的地形和PSSM+LiSPSM阴影算法

OGRE版本1.7.1的Sample里包含了地形的示例，且用到了PSSM+LiSPSM。

今天尝试把Character的Sinbad模型摆到地形上，不过模型的材质本身不支持PSSM。

看了下地形示例的实现，发现它在给Shader传PSSM分界点数据时，用了把模板材质clone一份，再设置diffusemap和pssm分界点的方法，相当让人无语....

MaterialPtr ret = MaterialManager::getSingleton().getByName(matName);

MaterialPtr baseMat = MaterialManager::getSingleton().getByName("Ogre/shadow/depth/integrated/pssm");

ret = baseMat->clone(matName);

Pass* p = ret->getTechnique(0)->getPass(0);

p->getTextureUnitState("diffuse")->setTextureName(textureName);

Vector4 splitPoints;

const PSSMShadowCameraSetup::SplitPointList& splitPointList =

static_cast<PSSMShadowCameraSetup*>(mPSSMSetup.get())->getSplitPoints();

for (int i = 0; i < 3; ++i)

{

splitPoints[i] = splitPointList[i];

}

p->getFragmentProgramParameters()->setNamedConstant("pssmSplitPoints", splitPoints); 

如果有几百种不同贴图的物件，就得在代码里手动为每一个物件设置diffusemap和pssm分界点，前者其实在材质脚本中可以用继承来覆盖，后者其实整个场景用到的数据都是一样的。好在OGRE增加了shared_params，可以多个shader共享相同的参数，在代码里只设置一遍就可以了。

修改后的fp:

shared_params pssm_params

{

shared_param_named pssmSplitPoints float4

}

fragment_program Ogre/shadow/receiver/depth/pssm3/fp cg

{

source depthshadowobject.cg

profiles ps_2_x arbfp1

entry_point main_fp

compile_arguments -DSHADOWCASTER=0 -DDEPTH_SHADOWCASTER=0 -DDEPTH_SHADOWRECEIVER=1

default_params

{

param_named_auto materialAmbient derived_ambient_light_colour

// shadow samplers are indexes 1/2/3

param_named_auto inverseShadowmapSize0 inverse_texture_size 1

param_named_auto inverseShadowmapSize1 inverse_texture_size 2

param_named_auto inverseShadowmapSize2 inverse_texture_size 3

//SET THIS MANUALLY!

//param_named pssmSplitPoints 0 0 0 0

shared_params_ref pssm_params

}

} 

c++:

Vector4 splitPoints;

const PSSMShadowCameraSetup::SplitPointList& splitPointList =

static_cast<PSSMShadowCameraSetup*>(mPSSMSetup.get())->getSplitPoints();

for (int i = 0; i < 3; ++i)

{

splitPoints[i] = splitPointList[i];

}

GpuSharedParametersPtr p = GpuProgramManager::getSingleton().getSharedParameters("pssm_params");

p->setNamedConstant("pssmSplitPoints", splitPoints);