SDL游戏之路(八)--2D游戏添加3D元素

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3D游戏如何制作呢？

2D游戏场景中加入3D元素怎么实现呢？

我的问题是，一个SDL写的2D游戏，如何在适当的地方添加3D元素？

经过不断的尝试和google，这个问题也解决了。

第一步：创建的SDL2的窗口，视图需要和OpenGL的结合起来。

代码例子如下：

int SkComm::init() {#ifndef __WP8__#ifdef __SKYPARK_IPHONE__int iRet = SDL_Init(SDL_INIT_VIDEO);#else#ifdef __SKYPARK_LINUX__int iRet = SDL_Init(SDL_INIT_VIDEO);#elseint iRet = SDL_Init(SDL_INIT_EVERYTHING);#endif#endifif (iRet < 0) {return -1;}iRet = TTF_Init();if (iRet < 0) {return -2;}int iPos = 0;#ifdef __SKYPARK_WIN__iPos = 40;int skypark_ScreenWidth = 800;int skypark_ScreenHeight = 600;#endif#ifdef __ANDROID__int skypark_ScreenWidth = Android_ScreenWidth;int skypark_ScreenHeight = Android_ScreenHeight;#endif#ifdef __SKYPARK_MAC__iPos = 40;int skypark_ScreenWidth = 800;int skypark_ScreenHeight = 600;#endif#ifdef __SKYPARK_IPHONE__int skypark_ScreenWidth = 480;int skypark_ScreenHeight = 320;#endif#ifdef __SKYPARK_LINUX__iPos = 40;int skypark_ScreenWidth = 800;int skypark_ScreenHeight = 600;#endif#ifdef HAVE_OPENGLSDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); //设置GL版本的SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1);//设置多缓存的个数SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);//设置深度缓存大小的，另外如果讲24改成32你会发现性能会下降很多很多很多很多的。m_screen_window = SDL_CreateWindow("skypark", iPos, iPos,skypark_ScreenWidth, skypark_ScreenHeight, SDL_WINDOW_OPENGL);#elsem_screen_window = SDL_CreateWindow("skypark", iPos, iPos,skypark_ScreenWidth, skypark_ScreenHeight, SDL_WINDOW_SHOWN);#endifif (m_screen_window == NULL) {return -3;}#ifdef HAVE_OPENGLm_glcontext = SDL_GL_CreateContext(m_screen_window);int oglIdx = -1;int nRD = SDL_GetNumRenderDrivers();for(int i=0; i<nRD; i++){SDL_RendererInfo info;if(!SDL_GetRenderDriverInfo(i, &info)){if(!strcmp(info.name, "opengl")){oglIdx = i;}}}m_screen_renderer = SDL_CreateRenderer(m_screen_window, oglIdx,SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC);#elsem_screen_renderer = SDL_CreateRenderer(m_screen_window, -1,SDL_RENDERER_ACCELERATED);#endifif (m_screen_renderer == NULL) {return -4;}g_SP.setScreen(skypark_ScreenWidth, skypark_ScreenHeight);#elsem_screen_renderer = &g_SkRenderer;#endifreturn 0;}

第二步：

如何实现坐标的统一呢？

上一章我们已经实现了平台的坐标自适应。所有我们当然希望在3D场景中，坐标也是自适应的。

如何做到呢？我们创建3D游戏场景的坐标顶点，取窗口的一半，就可以了。代码如下：

{//g_SkComm.log("[%s][%d]context=%d", __FILE__, __LINE__, context);glMatrixMode(GL_PROJECTION | GL_MODELVIEW);glLoadIdentity();//坐标统一，设置大小为窗口一半glOrtho(-g_iScreenWidthHalf, g_iScreenWidthHalf, g_iScreenHeightHalf,-g_iScreenHeightHalf, -1000, 1000);sk_gl_setOrtho(-g_iScreenWidthHalf, g_iScreenWidthHalf,g_iScreenHeightHalf, -g_iScreenHeightHalf, 0, 1);}

第三步：

在游戏绘图线程中，绘制2D和绘制3D相互结合：

主循环：

while (true) {SkEvent event;while (g_SkComm.poll_event(&event)) {g_SkGame.doEvent(&event);}Sint64 iCurTime = g_SkGameTimer.getGameMTime();while (g_SkGameTimer.m_siGameLastTime + g_SkGameTimer.siGameLoopMsec< iCurTime) {g_SkGameTimer.m_siGameLastTime += g_SkGameTimer.siGameLoopMsec;g_SkGameThread.run(g_SkGameTimer.m_siGameLastTime);}bool bShow = true;while (siShowBegin + g_SkGameTimer.siShowLoopMsec < iCurTime) {siShowBegin += g_SkGameTimer.siShowLoopMsec;if (bShow) {//g_SkGame.show(&g_SkShow);{Render();}g_SkShow.flush();bShow = false;}}//g_SkComm.log("[%s][%d]\n", __FILE__, __LINE__);//g_SkComm.msleep(3000);g_SkComm.msleep(SkGameTimer::siGameManLoopMsec);}

游戏内容绘制：

static void Render() {//绘制2D的游戏场景glPushMatrix();glLoadIdentity();glOrtho(-g_iScreenWidthHalf, g_iScreenWidthHalf, g_iScreenHeightHalf,-g_iScreenHeightHalf, -1000, 1000);g_SkGame.show(&g_SkShow);glPopMatrix();glRotatef(5.0, 1.0, 1.0, 1.0);//绘制3D的三角{float x = 30.0, y = 30.0;glBegin (GL_TRIANGLES);glColor3f(1.0, 0.0, 0.0);glVertex2f(x, y + 90.0);glColor3f(0.0, 1.0, 0.0);glVertex2f(x + 90.0, y - 90.0);glColor3f(0.0, 0.0, 1.0);glVertex2f(x - 90.0, y - 90.0);glEnd();}//绘制3D的立方体draw3D();}

static void draw3D() {static float color[8][3] = { { 1.0, 1.0, 0.0 }, { 1.0, 0.0, 0.0 }, { 0.0,0.0, 0.0 }, { 0.0, 1.0, 0.0 }, { 0.0, 1.0, 1.0 }, { 1.0, 1.0, 1.0 },{ 1.0, 0.0, 1.0 }, { 0.0, 0.0, 1.0 } };static float cube[8][3] = { { 50, 50, -50 }, { 50, -50, -50 }, { -50, -50,-50 }, { -50, 50, -50 }, { -50, 50, 50 }, { 50, 50, 50 }, { 50, -50,50 }, { -50, -50, 50 } };/* Do our drawing, too. *///glClearColor(0.0, 0.0, 0.0, 1.0);//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);glBegin (GL_QUADS);glColor3f(1.0, 0.0, 0.0);glVertex3fv(cube[0]);glVertex3fv(cube[1]);glVertex3fv(cube[2]);glVertex3fv(cube[3]);glColor3f(0.0, 1.0, 0.0);glVertex3fv(cube[3]);glVertex3fv(cube[4]);glVertex3fv(cube[7]);glVertex3fv(cube[2]);glColor3f(0.0, 0.0, 1.0);glVertex3fv(cube[0]);glVertex3fv(cube[5]);glVertex3fv(cube[6]);glVertex3fv(cube[1]);glColor3f(0.0, 1.0, 1.0);glVertex3fv(cube[5]);glVertex3fv(cube[4]);glVertex3fv(cube[7]);glVertex3fv(cube[6]);glColor3f(1.0, 1.0, 0.0);glVertex3fv(cube[5]);glVertex3fv(cube[0]);glVertex3fv(cube[3]);glVertex3fv(cube[4]);glColor3f(1.0, 0.0, 1.0);glVertex3fv(cube[6]);glVertex3fv(cube[1]);glVertex3fv(cube[2]);glVertex3fv(cube[7]);glEnd();//glMatrixMode (GL_MODELVIEW);//glRotatef(5.0, 1.0, 1.0, 1.0);}

好了，到这里，我们就实现了，在2D的游戏场景里面添加了2个3D的元素。

效果图如下：（蓝色部分为游戏全部场景）

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