ultimatepp/uppsrc/GLCtrl/GLPicking.cpp

#include "GLCtrl.h"

NAMESPACE_UPP

void GLCtrl::GLPicking::InitPickMatrix()
{
	if (_isPicking)
	{
		GLint viewport[4];
		glGetIntegerv(GL_VIEWPORT, viewport);
		gluPickMatrix(_pickPoint.x, viewport[3] - _pickPoint.y, 3, 3, viewport);
	}
}

Vector<int> GLCtrl::GLPicking::Pick(int x, int y, Callback resizeCallback, Callback paintCallback) 
{
	GLuint buffer[_bufferSize];
	
	_pickPoint = Point(x, y);
	
	glSelectBuffer(_bufferSize, buffer);
	glRenderMode(GL_SELECT);
	
	_isPicking = true;
	resizeCallback();
	
	glInitNames();
	paintCallback();
	
	_isPicking = false;
	resizeCallback();
	
	// returning to normal rendering mode
	int hits = glRenderMode(GL_RENDER);
	
	if (hits == 0)
		return Vector<int>();
	else 
		return ParseHits(buffer, hits);
}

Vector<int> GLCtrl::GLPicking::ParseHits(GLuint *buffer, int hits)
{
	GLuint *minPtr = buffer;
	
	for (int i = 0; i < hits; i++)
	{
		if (*(buffer + 1) < *(minPtr + 1))
			minPtr = buffer;
		
		buffer += *buffer + 3;
	}
	
	Vector<int> result;
	for (GLuint i = 0; i < *minPtr; i++)
		result.Add(*(minPtr + 3 + i));
	
	return result;
}

END_UPP_NAMESPACE