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CroCodile
06-04-2013, 10:48 AM
My project is simply detecting if there is overlap between a square and the mouse position. I think this is a good start to understand the collision principle. After drawing the stuff in the board to understand the concept, I came up with the following
X_mouse < x_max && X_mouse > x_min && Y_mouse < y_max && Y_mouse > y_min
This means overlapping for sure. But the problem I'm getting is if I move the mouse to the shape I'm getting different vertices. Also, the problem is getting worse if the window is reshaped.
Let say x_min = 20, x_max = 80, y_min = 20, y_max = 80
If I move the mouse to the shape then x_min = 100 and so on for the other vertices. Why this is the case? Please correct me if I'm going in the correct way with collision at least with my case.

#ifdef _WIN64
#pragma warning (disable:4996)
#endif

#if defined(WIN32)
# include <windows.h>
#endif

#include <iostream>
#include <GL/glut.h>

int const window_Height = 500, window_Width = 500;

static int x_min = 20.0, y_min = 20.0, x_max = 80.0, y_max = 80.0;
static int X_mouse, Y_mouse;

/* Glut Functions */
void glutDisplay(void);
void glutReshape(int width, int height);
void glutIdle(void);
void Mouse_Movement(int x, int y)
{
X_mouse = x;
Y_mouse = window_Height - y;
}

int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(window_Width, window_Height);
glutInitWindowPosition(100, 100);
glutCreateWindow ("square.cpp");
glutDisplayFunc(glutDisplay);
glutReshapeFunc(glutReshape);
glutIdleFunc(glutIdle);
glutPassiveMotionFunc(Mouse_Movement);
glutMainLoop();
}

void glutDisplay(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

if ( X_mouse < x_max && X_mouse > x_min && Y_mouse < y_max && Y_mouse > y_min )
{
std::cout << "Collision has been detected : " << "< " << X_mouse << " , " << Y_mouse << " > " <<std::endl;
}

else
{
std::cout << "No Collision " << "< " << X_mouse << " , " << Y_mouse << " > " <<std::endl;
}
glBegin(GL_POLYGON);
glVertex3f(x_min, y_min, 0.0);
glVertex3f(x_max, y_min, 0.0);
glVertex3f(x_max, y_max, 0.0);
glVertex3f(x_min, y_max, 0.0);
glEnd();

glFlush();
}

void glutReshape(int width, int height)
{
glViewport(0, 0, (GLsizei)width, (GLsizei)height);
glMatrixMode(GL_PROJECTION);
glOrtho(0.0, 100.0, 0.0, 100.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);