// OPEN_GL_test.cpp : Defines the entry point for the console application.
//
// OPEN_GL_test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#define GL_PI 3.1415f

GLfloat xRot = 0.45f;
GLfloat yRot = 0.35f;
GLboolean bCull = glIsEnabled(GL_CULL_FACE);
GLboolean bDepth= glIsEnabled(GL_DEPTH_TEST);
GLboolean bOutline=(GLboolean)true;

GLenum shademode = GL_FLAT;

GLfloat ex=0.0f;
GLfloat ey=0.0f;
GLfloat ez=-120.0f;
GLfloat delta= 0.01f;
GLfloat deltaR= 0.01f;


///////////////////////////////////////////////////////////


void SetupRC()
    {
    // Black background
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f );

    // Set drawing color to green
    glColor3f(0.0f, 1.0f, 0.0f);

    // Set color shading model to flat
    glShadeModel(shademode);

    // Clockwise-wound polygons are front facing; this is reversed
    // because we are using triangle fans
    glFrontFace(GL_CW);
    }

// Called to draw scene

void RenderScene(void)
    {
		// Reset coordinate system
   
    glLoadIdentity();
	gluLookAt (ex, ey, ez, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

    GLfloat x,y,angle;         // Storage for coordinates and angles
    int iPivot = 1;            // Used to flag alternating colors

    // Clear the window and the depth buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // Turn culling on if flag is set
    if(bCull)   glEnable(GL_CULL_FACE);
    else        glDisable(GL_CULL_FACE);

    // Enable depth testing if flag is set
    if(bDepth)  glEnable(GL_DEPTH_TEST);
    else        glDisable(GL_DEPTH_TEST);

    // Draw the back side as a wireframe only, if flag is set
    if(bOutline)glPolygonMode(GL_BACK,GL_LINE);
    else        glPolygonMode(GL_BACK,GL_FILL);

    // Save matrix state and do the rotation
    glPushMatrix();
    glRotatef(xRot, 1.0f, 0.0f, 0.0f);
    glRotatef(yRot, 0.0f, 1.0f, 0.0f);

    // Begin a triangle fan
    glBegin(GL_TRIANGLE_FAN);

    // Pinnacle of cone is shared vertex for fan, moved up z-axis
    // to produce a cone instead of a circle
    glVertex3f(0.0f, 0.0f, 75.0f);

    // Loop around in a circle and specify even points along the circle
    // as the vertices of the triangle fan

    for(angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI/8.0f))

        {
        // Calculate x and y position of the next vertex
        x = 50.0f*sin(angle);
        y = 50.0f*cos(angle);

        // Alternate color between red and green

        if((iPivot %2) == 0)    glColor3f(0.0f, 1.0f, 0.0f);
        else			        glColor3f(1.0f, 0.0f, 0.0f);

        // Increment pivot to change color next time
        iPivot++;

        // Specify the next vertex for the triangle fan
        glVertex2f(x, y);
        }

    // Done drawing fan for cone
    glEnd();

    // Begin a new triangle fan to cover the bottom
    glBegin(GL_TRIANGLE_FAN);

    // Center of fan is at the origin
    glVertex2f(0.0f, 0.0f);

    for(angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI/8.0f))
        {
        // Calculate x and y position of the next vertex
        x = 50.0f*sin(angle);
        y = 50.0f*cos(angle);

        // Alternate color between red and green
        if((iPivot %2) == 0)
            glColor3f(0.0f, 1.0f, 0.0f);
        else
            glColor3f(1.0f, 0.0f, 0.0f);

		// Increment pivot to change color next time
        iPivot++;

        // Specify the next vertex for the triangle fan
        glVertex2f(x, y);
        }

    // Done drawing the fan that covers the bottom
    glEnd();

    // Restore transformations
    glPopMatrix();

    // Flush drawing commands
     glutSwapBuffers();
    }

// Called by GLUT library when the window has changed size

void ChangeSize(GLsizei w, GLsizei h)
    {    // Set Viewport to window dimensions
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);

	glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    
	//glOrtho (-100.0, 100.0, -100, 100, -270.0, 270.0);
	//glFrustum (-1.0, 1.0, -1.0, 1.0, 1.5, 20.0);
	gluPerspective(60.0, 1.0, 1.5, 500.0);
	glMatrixMode (GL_MODELVIEW);	
    }



void SpecialKeys(int key, int x, int y)
    {GLfloat dx, dz;
    

	if(key == GLUT_KEY_UP)
	{//increase distance from camera to origin
		ex*=(1.0f+deltaR);  ey*=(1.0f+deltaR);	ez*=(1.0f+deltaR);
	}

    if(key == GLUT_KEY_DOWN)
	{//reduce distance from camera to origin (close up)
		ex*=(1.0f-deltaR); ey*=(1.0f-deltaR);	ez*=(1.0f-deltaR);}

    if(key == GLUT_KEY_LEFT)
		//Rotate camera around origin in Oxz plane
	{dx=-ez;     dz= ex;
     GLfloat s=sqrtf(ex*ex+ey*ey+ez*ez);
		ex+=delta*dx;       ez+=delta*dz;
	GLfloat s1=sqrtf(ex*ex+ey*ey+ez*ez)/s;
	ex/=s1;	ey/=s1;	ey/=s1;
	}

    if(key == GLUT_KEY_RIGHT)
		//Rotate camera around origin in Oxz plane
	{dx=-ez;     dz= ex;
     GLfloat s=sqrtf(ex*ex+ey*ey+ez*ez);
		ex-=delta*dx;      	ez-=delta*dz;
	GLfloat s1=sqrtf(ex*ex+ey*ey+ez*ez)/s;
	ex/=s1;	ey/=s1;	ey/=s1;}


    if(key ==  GLUT_KEY_F1) bCull=!bCull;
	if(key ==  GLUT_KEY_F2)bDepth=!bDepth;
    if(key ==  GLUT_KEY_F3)bOutline=!bOutline;
	if(key ==  GLUT_KEY_F4)
	{	if(shademode == GL_FLAT){shademode =GL_SMOOTH;}
		else {if(shademode == GL_SMOOTH){shademode =GL_FLAT;}};
		glShadeModel(shademode);
	}
    // Refresh the Window
    glutPostRedisplay();


    // Refresh the Window
    glutPostRedisplay();
    }


///////////////////////////////////////////////////////////



int main(int argc, char** argv)
{
glutInit(&argc, argv);
 glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize (200, 200);
glutInitWindowPosition (100, 100);
 glutCreateWindow (argv[0]);
 glutDisplayFunc(RenderScene);
    glutReshapeFunc(ChangeSize);
	 glutSpecialFunc (SpecialKeys);
	 
    SetupRC();
    glutMainLoop();
return 0;
}