nuclear@0: #include <stdio.h>
nuclear@0: #include <stdlib.h>
nuclear@0: #include <stdarg.h>
nuclear@0: #include <assert.h>
nuclear@0: #include <GL/glut.h>
nuclear@0: #include <vmath/vmath.h>
nuclear@0: #include <drawtext.h>
nuclear@0: 
nuclear@0: bool init();
nuclear@0: void display();
nuclear@0: void draw_grid();
nuclear@1: void draw_frustum();
nuclear@0: void draw_label(const Vector2 &pos, const char *fmt, ...);
nuclear@0: void reshape(int x, int y);
nuclear@0: void keyb(unsigned char key, int x, int y);
nuclear@0: void keyb_up(unsigned char key, int x, int y);
nuclear@0: void mouse(int bn, int st, int x, int y);
nuclear@0: void motion(int x, int y);
nuclear@0: Vector2 screen_to_world(int x, int y);
nuclear@1: Vector2 project(const Vector2 &v);
nuclear@1: Vector2 unproject(const Vector2 &v);
nuclear@2: float calc_proj_dist(float fov);
nuclear@0: 
nuclear@0: int win_xsz, win_ysz;
nuclear@0: float aspect;
nuclear@0: 
nuclear@0: Matrix4x4 proj;
nuclear@2: float proj_offset;
nuclear@0: Vector2 cur_point;
nuclear@0: bool cur_point_valid;
nuclear@0: 
nuclear@1: float proj_near = 0.5, proj_far = 50.0;
nuclear@2: float proj_vfov = 60.0;
nuclear@1: 
nuclear@0: bool keystate[256];
nuclear@2: bool bnstate[16];
nuclear@2: int prev_x, prev_y;
nuclear@2: unsigned int modkeys;
nuclear@2: 
nuclear@0: dtx_font *font;
nuclear@2: float pan[2] = {0, 0.85}, zoom = 0.3;
nuclear@2: float snap_dist = 0.25;
nuclear@0: 
nuclear@0: int main(int argc, char **argv)
nuclear@0: {
nuclear@0: 	glutInit(&argc, argv);
nuclear@0: 	glutInitWindowSize(1024, 768);
nuclear@0: 	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_MULTISAMPLE);
nuclear@0: 	glutCreateWindow("Interactive projection diagram");
nuclear@0: 
nuclear@0: 	glutDisplayFunc(display);
nuclear@0: 	glutReshapeFunc(reshape);
nuclear@0: 	glutKeyboardFunc(keyb);
nuclear@0: 	glutKeyboardUpFunc(keyb_up);
nuclear@0: 	glutMouseFunc(mouse);
nuclear@0: 	glutMotionFunc(motion);
nuclear@0: 
nuclear@0: 	if(!init()) {
nuclear@0: 		return 1;
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	glutMainLoop();
nuclear@0: 	return 0;
nuclear@0: }
nuclear@0: 
nuclear@0: bool init()
nuclear@0: {
nuclear@0: 	if(!(font = dtx_open_font("data/font.ttf", 16))) {
nuclear@0: 		fprintf(stderr, "failed to open font\n");
nuclear@0: 		return false;
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	glEnable(GL_MULTISAMPLE);
nuclear@1: 	proj.set_perspective(DEG_TO_RAD(proj_vfov), 1, 1.0, 50.0);
nuclear@2: 	proj.translate(Vector3(proj_offset, 0, 0));
nuclear@0: 	return true;
nuclear@0: }
nuclear@0: 
nuclear@0: void display()
nuclear@0: {
nuclear@0: 	glClear(GL_COLOR_BUFFER_BIT);
nuclear@0: 
nuclear@0: 	glMatrixMode(GL_MODELVIEW);
nuclear@0: 	glLoadIdentity();
nuclear@0: 	glTranslatef(-pan[0], -pan[1], 0);
nuclear@0: 	glScalef(zoom, zoom, zoom);
nuclear@0: 
nuclear@0: 	draw_grid();
nuclear@0: 
nuclear@1: 	draw_frustum();
nuclear@1: 
nuclear@0: 	if(cur_point_valid) {
nuclear@1: 		Vector2 ppt = project(cur_point);
nuclear@1: 
nuclear@0: 		glPointSize(7.0);
nuclear@0: 		glBegin(GL_POINTS);
nuclear@0: 		glColor3f(0.2, 1, 0.2);
nuclear@0: 		glVertex2f(cur_point.x, cur_point.y);
nuclear@1: 		glColor3f(0.7, 0.2, 0.2);
nuclear@1: 		glVertex2f(ppt.x, ppt.y);
nuclear@0: 		glEnd();
nuclear@0: 
nuclear@1: 		glEnable(GL_LINE_STIPPLE);
nuclear@1: 		glLineStipple(4, 0xe0e0);
nuclear@1: 
nuclear@1: 		glBegin(GL_LINES);
nuclear@1: 		glColor3f(0.2, 0.5, 0.2);
nuclear@1: 		glVertex2f(cur_point.x, cur_point.y);
nuclear@1: 		glColor3f(0.5, 0.2, 0.2);
nuclear@1: 		glVertex2f(ppt.x, ppt.y);
nuclear@1: 		glEnd();
nuclear@1: 		glDisable(GL_LINE_STIPPLE);
nuclear@1: 
nuclear@2: 		glColor3f(0.2, 0.5, 0.2);
nuclear@0: 		draw_label(cur_point, "(%.2f, %.2f)", cur_point.x, cur_point.y);
nuclear@2: 		glColor3f(0.5, 0.2, 0.2);
nuclear@1: 		draw_label(ppt, "(%.2f, %.2f)", ppt.x, ppt.y);
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	glutSwapBuffers();
nuclear@0: 	assert(glGetError() == GL_NO_ERROR);
nuclear@0: }
nuclear@0: 
nuclear@0: #define LINE(x0, y0, x1, y1)	(glVertex2f(x0, y0), glVertex2f(x1, y1))
nuclear@0: 
nuclear@0: void draw_grid()
nuclear@0: {
nuclear@1: 	float ymin = -10;
nuclear@1: 	float ymax = 10;
nuclear@1: 	float xmin = -10;
nuclear@1: 	float xmax = 10;
nuclear@1: 	float ticksz = 0.015 / zoom;
nuclear@0: 
nuclear@0: 	glBegin(GL_LINES);
nuclear@0: 	glColor3f(1, 1, 1);
nuclear@1: 	LINE(0, -10, 0, 10);
nuclear@1: 	LINE(-10, 0, 10, 0);
nuclear@0: 
nuclear@0: 	for(int i=1; i<11; i++) {
nuclear@0: 		for(int j=0; j<2; j++) {
nuclear@1: 			float x = 10.0 * (float)i / 10.0 * (j ? -1.0 : 1.0);
nuclear@0: 
nuclear@0: 			glColor3f(0.15, 0.15, 0.15);
nuclear@0: 			LINE(x, ymin, x, ymax);
nuclear@0: 			LINE(xmin, x, xmax, x);
nuclear@0: 
nuclear@0: 			glColor3f(0.4, 0.4, 0.4);
nuclear@0: 			LINE(x, -ticksz, x, ticksz);
nuclear@0: 			LINE(-ticksz, x, ticksz, x);
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 	glEnd();
nuclear@0: }
nuclear@0: 
nuclear@1: void draw_frustum()
nuclear@1: {
nuclear@2: 	Vector2 left[2], right[2];
nuclear@1: 
nuclear@1: 	glBegin(GL_LINES);
nuclear@1: 	glColor3f(0.2, 0.4, 0.8);
nuclear@1: 
nuclear@2: 	right[0] = unproject(Vector2(1, 0));
nuclear@2: 	right[1] = unproject(Vector2(1, 1));
nuclear@2: 	LINE(right[0].x, right[0].y, right[1].x, right[1].y);
nuclear@1: 
nuclear@2: 	left[0] = unproject(Vector2(-1, 0));
nuclear@2: 	left[1] = unproject(Vector2(-1, 1));
nuclear@2: 	LINE(left[0].x, left[0].y, left[1].x, left[1].y);
nuclear@1: 
nuclear@2: 	float dist = calc_proj_dist(proj_vfov);
nuclear@2: 	LINE(-1, dist, 1, dist);
nuclear@2: 	glEnd();
nuclear@1: 
nuclear@2: 	/* find the points where the frustum lines hit zero */
nuclear@2: 	glEnable(GL_LINE_STIPPLE);
nuclear@2: 	glLineStipple(3, 0x0101);
nuclear@2: 
nuclear@2: 	glBegin(GL_LINES);
nuclear@2: 	for(int i=0; i<2; i++) {
nuclear@2: 		Vector2 *v = i ? left : right;
nuclear@2: 		float t = -v[1].y / (v[0].y - v[1].y);
nuclear@2: 		float x = v[1].x + (v[0].x - v[1].x) * t;
nuclear@2: 		LINE(v[0].x, v[0].y, x, 0);
nuclear@2: 	}
nuclear@1: 	glEnd();
nuclear@2: 	glDisable(GL_LINE_STIPPLE);
nuclear@1: }
nuclear@1: 
nuclear@0: void draw_label(const Vector2 &pos, const char *fmt, ...)
nuclear@0: {
nuclear@0: 	static char buf[512];
nuclear@0: 	va_list ap;
nuclear@0: 
nuclear@0: 	va_start(ap, fmt);
nuclear@0: 	vsnprintf(buf, sizeof buf - 1, fmt, ap);
nuclear@0: 	va_end(ap);
nuclear@0: 
nuclear@0: 	glPushMatrix();
nuclear@0: 	glTranslatef(pos.x + 0.01, pos.y + 0.01, 0);
nuclear@0: 	float s = 2.0 / (win_ysz * zoom);
nuclear@0: 	glScalef(s, s, s);
nuclear@0: 
nuclear@0: 	dtx_string(buf);
nuclear@0: 
nuclear@0: 	glPopMatrix();
nuclear@0: }
nuclear@0: 
nuclear@0: void reshape(int x, int y)
nuclear@0: {
nuclear@0: 	win_xsz = x;
nuclear@0: 	win_ysz = y;
nuclear@0: 	aspect = (float)x / (float)y;
nuclear@0: 
nuclear@0: 	glViewport(0, 0, x, y);
nuclear@0: 
nuclear@0: 	glMatrixMode(GL_PROJECTION);
nuclear@0: 	glLoadIdentity();
nuclear@0: 	glScalef(1.0 / aspect, 1.0, 1.0);
nuclear@0: }
nuclear@0: 
nuclear@0: void keyb(unsigned char key, int x, int y)
nuclear@0: {
nuclear@0: 	keystate[key] = 1;
nuclear@2: 	modkeys = glutGetModifiers();
nuclear@0: 
nuclear@0: 	switch(key) {
nuclear@0: 	case 27:
nuclear@0: 		exit(0);
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void keyb_up(unsigned char key, int x, int y)
nuclear@0: {
nuclear@0: 	keystate[key] = 0;
nuclear@2: 	modkeys = glutGetModifiers();
nuclear@0: }
nuclear@0: 
nuclear@0: void mouse(int bn, int st, int x, int y)
nuclear@0: {
nuclear@0: 	bnstate[bn - GLUT_LEFT_BUTTON] = st == GLUT_DOWN;
nuclear@0: 	prev_x = x;
nuclear@0: 	prev_y = y;
nuclear@2: 	modkeys = glutGetModifiers();
nuclear@0: 
nuclear@0: 	if(bn == GLUT_LEFT_BUTTON && st == GLUT_DOWN) {
nuclear@0: 		cur_point = screen_to_world(x, y);
nuclear@0: 		cur_point_valid = true;
nuclear@0: 		glutPostRedisplay();
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void motion(int x, int y)
nuclear@0: {
nuclear@0: 	float dx = 2.0 * aspect * (x - prev_x) / (float)win_xsz;
nuclear@0: 	float dy = 2.0 * (y - prev_y) / (float)win_ysz;
nuclear@0: 	prev_x = x;
nuclear@0: 	prev_y = y;
nuclear@0: 
nuclear@0: 	if(bnstate[0]) {
nuclear@0: 		cur_point = screen_to_world(x, y);
nuclear@2: 		if(keystate['s'] || keystate['S']) {
nuclear@2: 			cur_point.x = round(cur_point.x / snap_dist) * snap_dist;
nuclear@2: 			cur_point.y = round(cur_point.y / snap_dist) * snap_dist;
nuclear@2: 		}
nuclear@0: 		glutPostRedisplay();
nuclear@0: 	}
nuclear@0: 	if(bnstate[1]) {
nuclear@0: 		pan[0] -= dx;
nuclear@0: 		pan[1] += dy;
nuclear@0: 
nuclear@0: 		glutPostRedisplay();
nuclear@0: 	}
nuclear@0: 	if(bnstate[2]) {
nuclear@0: 		zoom += dy;
nuclear@0: 
nuclear@0: 		if(zoom < 1e-4) zoom = 1e-4;
nuclear@0: 		glutPostRedisplay();
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: Vector2 screen_to_world(int px, int py)
nuclear@0: {
nuclear@1: 	/* canonical [-1, 1] system */
nuclear@1: 	float x = aspect * ((float)px * 2.0 / (float)win_xsz - 1.0);
nuclear@1: 	float y = (float)(win_ysz - py) * 2.0 / (float)win_ysz - 1.0;
nuclear@0: 
nuclear@1: 	/* account for pan & zoom */
nuclear@1: 	x = (x + pan[0]) / zoom;
nuclear@1: 	y = (y + pan[1]) / zoom;
nuclear@0: 
nuclear@0: 	return Vector2(x, y);
nuclear@0: }
nuclear@1: 
nuclear@1: Vector2 project(const Vector2 &v)
nuclear@1: {
nuclear@1: 	Vector4 ppt = Vector4(v.x, 0, -v.y, 1).transformed(proj);
nuclear@2: 	return Vector2(ppt.x / ppt.w, calc_proj_dist(proj_vfov));
nuclear@1: }
nuclear@1: 
nuclear@1: Vector2 unproject(const Vector2 &v)
nuclear@1: {
nuclear@1: 	Vector4 v4 = Vector4(v.x, 0.0, v.y, 1.0);
nuclear@1: 	Matrix4x4 inv_proj = proj.inverse();
nuclear@1: 
nuclear@1: 	Vector4 res4 = v4.transformed(inv_proj);
nuclear@1: 	return Vector2(res4.x / res4.w, -res4.z / res4.w);
nuclear@1: }
nuclear@2: 
nuclear@2: float calc_proj_dist(float fov)
nuclear@2: {
nuclear@2: 	return 1.0 / tan(DEG_TO_RAD(fov) / 2.0);
nuclear@2: }