PerspectivePoint

testApp.cpp

#include "testApp.h"

ofMesh points;
ofEasyCam cam;
bool use_perspective_point = true;

void enablePerspectivePoint(float size)
{
  static GLfloat distance[] = { 0.0, 0.0, 1.0 };
	glPointParameterfv(GL_POINT_DISTANCE_ATTENUATION, distance);
	
	GLfloat m[16];
	GLint viewport[4];
	
	glGetFloatv(GL_PROJECTION_MATRIX, m);
	glGetIntegerv(GL_VIEWPORT, viewport);
	
	float aspect = (float)viewport[2] / viewport[3];
	float a = (m[0] * aspect);
	float fov = (atan(a) - M_PI_2) * -2;
	float pixel_per_unit = fabs((float)viewport[3] / (2.0f * std::tan(fov * 0.5f)));
	
	glPointSize(pixel_per_unit * size);
}

void disablePerspectivePoint(float size)
{
	static GLfloat distance[] = { 1.0, 0.0, 0.0 };
	glPointParameterfv(GL_POINT_DISTANCE_ATTENUATION, distance);

	glPointSize(size);
}

//--------------------------------------------------------------
void testApp::setup()
{
	ofSetFrameRate(60);
	ofSetVerticalSync(true);
	ofBackground(0);
	
	for (int i = 0; i < 1000; i++)
	{
		ofVec3f p;
		p.x = ofRandom(-500, 500);
		p.y = ofRandom(-500, 500);
		p.z = 0;
		points.addVertex(p);
	}
}

//--------------------------------------------------------------
void testApp::update()
{

}

//--------------------------------------------------------------
void testApp::draw()
{
	ofEnableAlphaBlending();
	glEnable(GL_POINT_SMOOTH);
	
	if (use_perspective_point)
		enablePerspectivePoint(10);
	else
		disablePerspectivePoint(10);
	
	cam.begin();
	points.drawVertices();
	cam.end();
	
	string str = string("PerspectivePoint: ") + (use_perspective_point ? "ENABLE" : "DISABLE");
	ofDrawBitmapString(str, 10, 20);
}

//--------------------------------------------------------------
void testApp::keyPressed(int key)
{
	use_perspective_point = !use_perspective_point;
}

//--------------------------------------------------------------
void testApp::keyReleased(int key)
{

}

//--------------------------------------------------------------
void testApp::mouseMoved(int x, int y)
{

}

//--------------------------------------------------------------
void testApp::mouseDragged(int x, int y, int button)
{

}

//--------------------------------------------------------------
void testApp::mousePressed(int x, int y, int button)
{

}

//--------------------------------------------------------------
void testApp::mouseReleased(int x, int y, int button)
{

}

//--------------------------------------------------------------
void testApp::windowResized(int w, int h)
{

}

//--------------------------------------------------------------
void testApp::gotMessage(ofMessage msg)
{

}

//--------------------------------------------------------------
void testApp::dragEvent(ofDragInfo dragInfo)
{

}