Lesson2: Variables and Functions

Lesson 2 teaches you how to use engine variables and functions - please see the Engine Plugins chapter for details. All engine variables from the script language are available, and also most engine functions except script-specific functions like wait. Under C/C++ you normally don't use multitasking and thus won't and can't use the script multitasking functions. Instead, use the Windows Sleep() function for waiting a certain time, or the EVENT_FRAME for triggering an entity function every frame cycle.

// Lesson2: Using engine variables and functions
// Link to the engine library
#pragma comment(lib, "acknex.lib") // Include the usual Windows headers #define WIN32_LEAN_AND_MEAN #include <windows.h> #include <stdlib.h> #include <malloc.h> #include <memory.h> #include <tchar.h> // Include the engine data types, variables, and functions #include "var.h" // the var class - without it, you'd need _VAR() macros #include "adll.h int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { // The engine_open() function returns a pointer to a struct of // engine variables. We don't want to load a script or level here, // so we just pass NULL. ENGINE_VARS *ev = engine_open(NULL); if (!ev) return 1; // acknex.dll not found // Once we have the pointer to the ENGINE_VARS struct, we can use engine // functions for customizing the window, giving a level name to load, // assigning functions to buttons etc. // In our case we're now again loading the arena.wmb level. level_load("arena.wmb"); // We want to limit our frame rate to 50 frames per second. For this we // change an engine variable named fps_max: v(fps_max) = 50; // v() is a convenient macro to access engine variables. // It is defined in the adll.h header. // Now let's enter our main loop: while (engine_frame()) { // The first engine frame opens the DirectX device and // switches the engine window to DirectX mode. Therefore, // the time before the first frame is merely for setting // or defining variables - DirectX functions won't work yet. // Also the the level is actually loaded in the first frame. // The level_load() function just stored its name. // If we loaded a script before, it's main and starter // functions are also executed in the first engine_frame(). // We didn't pass a level name to engine_open(), so we now have to // program our own camera movement. // By default, a VIEW named "camera" is created when opening a level, // and can be moved by changing it's angle and position parameters. v(camera).pan += 3 * v(key_force).x; // left/right cursor keys v(camera).tilt += 3 * v(key_force).y; // up/down cursor keys // The key_force vector returns a value of +/-1 dependent on which // cursor keys in x and y direction are pressed. // The v() is another simple macro to access engine variables. // Now we want to move in the direction the camera is looking. // For movement with the WASD keys, we use the key_w, key_a, // key_s, key_d variables and calculate a movement vector. VECTOR vMove; // movement vector vMove.x = 6.0 * (v(key_w) - v(key_s)); // forward vMove.y = 6.0 * (v(key_a) - v(key_d)); // sideward vMove.z = 0; // Finally, we use engine vector functions to rotate the movement vector // by the camera angle, then add it to the camera position. // We can typecast any object's x position to a VECTOR and it's pan // orientation to an Euler ANGLE. vec_rotate (&vMove, (ANGLE*)&v(camera).pan); vec_add ((VECTOR*)&v(camera).x, &vMove); } // This simple movement was not as smooth as the default one, // but we're going to change this in our next lesson. engine_close(); return 0; }
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