1.1 --- a/main.cc	Sat Jan 24 16:36:34 2015 +0200
     1.2 +++ b/main.cc	Sat Jan 24 17:49:35 2015 +0200
     1.3 @@ -9,6 +9,7 @@
     1.4  bool init();
     1.5  void display();
     1.6  void draw_grid();
     1.7 +void draw_frustum();
     1.8  void draw_label(const Vector2 &pos, const char *fmt, ...);
     1.9  void reshape(int x, int y);
    1.10  void keyb(unsigned char key, int x, int y);
    1.11 @@ -16,6 +17,8 @@
    1.12  void mouse(int bn, int st, int x, int y);
    1.13  void motion(int x, int y);
    1.14  Vector2 screen_to_world(int x, int y);
    1.15 +Vector2 project(const Vector2 &v);
    1.16 +Vector2 unproject(const Vector2 &v);
    1.17  
    1.18  int win_xsz, win_ysz;
    1.19  float aspect;
    1.20 @@ -24,9 +27,12 @@
    1.21  Vector2 cur_point;
    1.22  bool cur_point_valid;
    1.23  
    1.24 +float proj_near = 0.5, proj_far = 50.0;
    1.25 +float proj_vfov = 50.0;
    1.26 +
    1.27  bool keystate[256];
    1.28  dtx_font *font;
    1.29 -float pan[2], zoom = 1.0;
    1.30 +float pan[2] = {0, 0.85}, zoom = 0.4;
    1.31  
    1.32  int main(int argc, char **argv)
    1.33  {
    1.34 @@ -58,7 +64,7 @@
    1.35  	}
    1.36  
    1.37  	glEnable(GL_MULTISAMPLE);
    1.38 -	proj.set_perspective(DEG_TO_RAD(60), 1, 0.5, 500.0);
    1.39 +	proj.set_perspective(DEG_TO_RAD(proj_vfov), 1, 1.0, 50.0);
    1.40  	return true;
    1.41  }
    1.42  
    1.43 @@ -73,15 +79,34 @@
    1.44  
    1.45  	draw_grid();
    1.46  
    1.47 +	draw_frustum();
    1.48 +
    1.49  	if(cur_point_valid) {
    1.50 +		Vector2 ppt = project(cur_point);
    1.51 +
    1.52  		glPointSize(7.0);
    1.53  		glBegin(GL_POINTS);
    1.54  		glColor3f(0.2, 1, 0.2);
    1.55  		glVertex2f(cur_point.x, cur_point.y);
    1.56 +		glColor3f(0.7, 0.2, 0.2);
    1.57 +		glVertex2f(ppt.x, ppt.y);
    1.58  		glEnd();
    1.59  
    1.60 +		glEnable(GL_LINE_STIPPLE);
    1.61 +		glLineStipple(4, 0xe0e0);
    1.62 +
    1.63 +		glBegin(GL_LINES);
    1.64 +		glColor3f(0.2, 0.5, 0.2);
    1.65 +		glVertex2f(cur_point.x, cur_point.y);
    1.66 +		glColor3f(0.5, 0.2, 0.2);
    1.67 +		glVertex2f(ppt.x, ppt.y);
    1.68 +		glEnd();
    1.69 +		glDisable(GL_LINE_STIPPLE);
    1.70 +
    1.71  		glColor3f(0.15, 0.5, 0.15);
    1.72  		draw_label(cur_point, "(%.2f, %.2f)", cur_point.x, cur_point.y);
    1.73 +		glColor3f(0.4, 0.1, 0.1);
    1.74 +		draw_label(ppt, "(%.2f, %.2f)", ppt.x, ppt.y);
    1.75  	}
    1.76  
    1.77  	glutSwapBuffers();
    1.78 @@ -92,20 +117,20 @@
    1.79  
    1.80  void draw_grid()
    1.81  {
    1.82 -	float ymin = -1;
    1.83 -	float ymax = 1;
    1.84 -	float xmin = -1;
    1.85 -	float xmax = 1;
    1.86 -	float ticksz = 0.015;
    1.87 +	float ymin = -10;
    1.88 +	float ymax = 10;
    1.89 +	float xmin = -10;
    1.90 +	float xmax = 10;
    1.91 +	float ticksz = 0.015 / zoom;
    1.92  
    1.93  	glBegin(GL_LINES);
    1.94  	glColor3f(1, 1, 1);
    1.95 -	LINE(0, -1, 0, 1);
    1.96 -	LINE(-1, 0, 1, 0);
    1.97 +	LINE(0, -10, 0, 10);
    1.98 +	LINE(-10, 0, 10, 0);
    1.99  
   1.100  	for(int i=1; i<11; i++) {
   1.101  		for(int j=0; j<2; j++) {
   1.102 -			float x = (float)i / 10.0 * (j ? -1.0 : 1.0);
   1.103 +			float x = 10.0 * (float)i / 10.0 * (j ? -1.0 : 1.0);
   1.104  
   1.105  			glColor3f(0.15, 0.15, 0.15);
   1.106  			LINE(x, ymin, x, ymax);
   1.107 @@ -119,6 +144,26 @@
   1.108  	glEnd();
   1.109  }
   1.110  
   1.111 +void draw_frustum()
   1.112 +{
   1.113 +	Vector2 v0, v1;
   1.114 +
   1.115 +	glBegin(GL_LINES);
   1.116 +	glColor3f(0.2, 0.4, 0.8);
   1.117 +
   1.118 +	v0 = unproject(Vector2(1, 0));
   1.119 +	v1 = unproject(Vector2(1, 1));
   1.120 +	LINE(v0.x, v0.y, v1.x, v1.y);
   1.121 +
   1.122 +	v0 = unproject(Vector2(-1, 0));
   1.123 +	v1 = unproject(Vector2(-1, 1));
   1.124 +	LINE(v0.x, v0.y, v1.x, v1.y);
   1.125 +
   1.126 +	LINE(-0.5, proj_near, 0.5, proj_near);
   1.127 +
   1.128 +	glEnd();
   1.129 +}
   1.130 +
   1.131  void draw_label(const Vector2 &pos, const char *fmt, ...)
   1.132  {
   1.133  	static char buf[512];
   1.134 @@ -209,11 +254,28 @@
   1.135  
   1.136  Vector2 screen_to_world(int px, int py)
   1.137  {
   1.138 -	float sx = 2.0 * aspect * (1.0 / zoom) / (float)win_xsz;
   1.139 -	float sy = 2.0 * (1.0 / zoom) / (float)win_ysz;
   1.140 +	/* canonical [-1, 1] system */
   1.141 +	float x = aspect * ((float)px * 2.0 / (float)win_xsz - 1.0);
   1.142 +	float y = (float)(win_ysz - py) * 2.0 / (float)win_ysz - 1.0;
   1.143  
   1.144 -	float x = (float)px * sx - (aspect + pan[0]) / zoom;
   1.145 -	float y = (float)(win_ysz - py) * sy - (1.0 + pan[1]) / zoom;
   1.146 +	/* account for pan & zoom */
   1.147 +	x = (x + pan[0]) / zoom;
   1.148 +	y = (y + pan[1]) / zoom;
   1.149  
   1.150  	return Vector2(x, y);
   1.151  }
   1.152 +
   1.153 +Vector2 project(const Vector2 &v)
   1.154 +{
   1.155 +	Vector4 ppt = Vector4(v.x, 0, -v.y, 1).transformed(proj);
   1.156 +	return Vector2(ppt.x / ppt.w, ppt.z / ppt.w);
   1.157 +}
   1.158 +
   1.159 +Vector2 unproject(const Vector2 &v)
   1.160 +{
   1.161 +	Vector4 v4 = Vector4(v.x, 0.0, v.y, 1.0);
   1.162 +	Matrix4x4 inv_proj = proj.inverse();
   1.163 +
   1.164 +	Vector4 res4 = v4.transformed(inv_proj);
   1.165 +	return Vector2(res4.x / res4.w, -res4.z / res4.w);
   1.166 +}