RTTPICKEr分析
本帖最后由 liyihongcug 于 2020-4-14 10:45 编辑RTTPICKEr 使用RTT 相机。
Picks objects using an RTT camera and Vertex Attributes.
说明如何操作
/**
* Starts a pick operation. When the operation completes, invokes the callback
* with the results. You can use this method if you want to use the picker directly
* WITHOUT installing it as an EventHandler. If you use it as an EventHandler, you
* do NOT need to call this method directly; the Picker will call it upon handling
* a pick event (i.e., when Callback::accept returns true).
*
* Returns true if the pick was succesfully queued; false if not.
*/
着色器源码
{
// SHADERS for the RTT pick camera.
const char* pickVertexEncode =
"#version " GLSL_VERSION_STR "\n"
"#pragma vp_entryPoint oe_pick_encodeObjectID\n"
"#pragma vp_location vertex_clip\n"
"uint oe_index_objectid; \n" // Vertex stage global containing the Object ID; set in ObjectIndex shader.
"flat out vec4 oe_pick_encoded_objectid; \n" // output encoded oid to fragment shader
"flat out int oe_pick_color_contains_objectid; \n"// whether color already contains oid (written by another RTT camera)
"void oe_pick_encodeObjectID(inout vec4 vertex) \n"
"{ \n"
" oe_pick_color_contains_objectid = (oe_index_objectid == 1u) ? 1 : 0; \n"
" if ( oe_pick_color_contains_objectid == 0 ) \n"
" { \n"
" float b0 = float((oe_index_objectid & 0xff000000u) >> 24u); \n"
" float b1 = float((oe_index_objectid & 0x00ff0000u) >> 16u); \n"
" float b2 = float((oe_index_objectid & 0x0000ff00u) >> 8u ); \n"
" float b3 = float((oe_index_objectid & 0x000000ffu) ); \n"
" oe_pick_encoded_objectid = vec4(b0, b1, b2, b3) / 255.0; \n"
" } \n"
"} \n";
const char* pickFragment =
"#version " GLSL_VERSION_STR "\n"
"#pragma vp_entryPoint oe_pick_renderEncodedObjectID\n"
"#pragma vp_location fragment_output\n"
"#pragma vp_order last\n"
"flat in vec4 oe_pick_encoded_objectid; \n"
"flat in int oe_pick_color_contains_objectid; \n"
"out vec4 fragColor; \n"
"void oe_pick_renderEncodedObjectID(inout vec4 color) \n"
"{ \n"
" if ( oe_pick_color_contains_objectid == 1 ) \n"
" fragColor = color; \n"
" else \n"
" fragColor = oe_pick_encoded_objectid; \n"
"} \n";
}
VirtualProgram*
RTTPicker::createRTTProgram()
{
VirtualProgram* vp = new VirtualProgram();
vp->setName( "osgEarth::RTTPicker" );
// Install RTT picker shaders:
ShaderPackage pickShaders;
pickShaders.add( "RTTPicker.vert.glsl", pickVertexEncode );
pickShaders.add( "RTTPicker.frag.glsl", pickFragment );
pickShaders.loadAll( vp );
// Install shaders and bindings from the ObjectIndex:
Registry::objectIndex()->loadShaders( vp );
return vp;
}
RTTPicker::RTTPicker(int cameraSize)
{
// group that will hold RTT children for all cameras
_group = new osg::Group();
// Size of the RTT camera image
_rttSize = std::max(cameraSize, 4);
// pixels around the click to test
_buffer = 2;
}
RTTPicker::~RTTPicker()
{
// remove the RTT camera from all views
for(int i=0; i<_pickContexts.size(); ++i)
{
PickContext& pc = _pickContexts;
while( pc._pickCamera->getNumParents() > 0 )
{
pc._pickCamera->getParent(0)->removeChild( pc._pickCamera.get() );
}
}
}
osgEarth::VirtualProgram在apply时用到了osg::Program，也就是VirtualProgram最终是要通过osg::Program实现着色器功能，只不过VirtualProgram中还封装了一些其他内容（比如继承、抽象属性，着色器代码管理等），方便使用而已。
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