SDL教程-003.SDL使用OpenGL渲染图形

SDL教程-003.SDL使用OpenGL渲染图形

SDL 集成OpenGL入门Demo

#include <iostream>  
#include <SDL/SDL.h>    
#include <GL/freeglut.h>
using namespace std;

const int SCREEN_WIDTH = 800;
const int SCREEN_HEIGHT = 600;
SDL_Window *mainwindow;
SDL_GLContext maincontext;

* and quits the application */
void sdldie(const char *msg)
{
	printf("%s: %s\n", msg, SDL_GetError());
	SDL_Quit();
	exit(1);
}

void quit(int code)
{
	SDL_Quit();
	exit(code);
}

void checkSDLError(int line = -1)
{
#ifndef NDEBUG  
	const char *error = SDL_GetError();
	if (*error != '\0')
	{
		printf("SDL Error: %s\n", error);
		if (line != -1)
			printf(" + line: %i\n", line);
		SDL_ClearError();
	}
#endif  
}

void initGL(int width, int height)
{
	float ratio = (float)width / (float)height;
	glShadeModel(GL_SMOOTH);
	glClearColor(0, 0, 0, 0); 
	glViewport(0, 0, width, height);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.0, ratio, 1.0, 100.0);
}

void initSDL()
{
	if (SDL_Init(SDL_INIT_VIDEO) < 0)
		sdldie("Unable to initialize SDL");

	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);

	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

	mainwindow = SDL_CreateWindow("OpenGL in SDL2", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
		SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
	if (!mainwindow)
		sdldie("Unable to create window");

	checkSDLError(__LINE__);

	maincontext = SDL_GL_CreateContext(mainwindow);
	checkSDLError(__LINE__);
	
	SDL_GL_SetSwapInterval(1);
}

void renderGL()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glTranslatef(0.0, 0.0, -5.0);
	glBegin(GL_QUADS);
	glColor3f(1.0f, 0.0f, 0.0f);
	glVertex3f(-1.0f, -1.0f, 1.0f);
	glColor3f(0.0f, 1.0f, 0.0f);
	glVertex3f(1.0f, -1.0f, 1.0f);
	glColor3f(0.0f, 0.0f, 1.0f);
	glVertex3f(1.0f, 1.0f, 1.0f);
	glColor3f(1.0f, 1.0f, 0.0f);
	glVertex3f(-1.0f, 1.0f, 1.0f);
	glEnd();
	SDL_GL_SwapWindow(mainwindow);
}

void resizeGL(int width, int height)
{
	if (height == 0)
	{
		height = 1;
	}
	glViewport(0, 0, (GLint)width, (GLint)height);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45.0, (GLfloat)width / (GLfloat)height, 0.1, 100.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

}

void handleKeyEvent(SDL_Keysym* keysym)
{
	switch (keysym->sym)
	{
	case SDLK_ESCAPE:
		quit(0);
		break;
	case SDLK_SPACE:
		cout << "Space" << endl;
		break;
	default:
		break;
	}
}

void handleEvents()
{
	SDL_Event event;
	while (SDL_PollEvent(&event)) {
		switch (event.type) {
		case SDL_KEYDOWN:
			handleKeyEvent(&event.key.keysym);
			break;
		case SDL_QUIT:
			quit(0);
			break;
		case SDL_WINDOWEVENT:
			if (event.window.event == SDL_WINDOWEVENT_RESIZED)
			{
				if (mainwindow)
				{
					int tmpX, tmpY;
					SDL_GetWindowSize(mainwindow, &tmpX, &tmpY);
					resizeGL(tmpX, tmpY);

				}
			}
			SDL_GL_SwapWindow(mainwindow);
			break;
		}
	}
}

int main(int argc, char *argv[])
{
	initSDL();
	initGL(SCREEN_WIDTH, SCREEN_HEIGHT);
	renderGL();
	while (true)
	{
		handleEvents();
		renderGL();
	}

	return 0;
}

SDL 集成freeglut+glew

#include <iostream>  
#include <SDL/SDL.h>    
#include <GL/glew.h>
#include <GL/freeglut.h>
using namespace std;

#ifdef _DEBUG
	#pragma comment( lib, "glew32d.lib" )  
#else if
	#pragma comment( lib, "glew32.lib" )  
#endif


bool quit;

SDL_Window* window;
SDL_GLContext glContext;
SDL_Event sdlEvent;

int main(int argc, char *argv[])
{
	std::cout << "你好" << std::endl;
	quit = false;

	//Use OpenGL 3.1 core
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

	// Initialize video subsystem
	if (SDL_Init(SDL_INIT_VIDEO) < 0)
	{
		// Display error message
		printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
		return false;
	}
	else
	{
		// Create window
		window = SDL_CreateWindow("Hello World!", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
		if (window == NULL)
		{
			// Display error message
			printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
			return false;
		}
		else
		{
			// Create OpenGL context
			glContext = SDL_GL_CreateContext(window);

			if (glContext == NULL)
			{
				// Display error message
				printf("OpenGL context could not be created! SDL Error: %s\n", SDL_GetError());
				return false;
			}
			else
			{
				// Initialize glew
				glewInit();
			}
		}
	}

	// Game loop
	while (!quit)
	{
		while (SDL_PollEvent(&sdlEvent) != 0)
		{
			// Esc button is pressed
			if (sdlEvent.type == SDL_QUIT)
			{
				quit = true;
			}
		}

		// Set background color as cornflower blue
		glClearColor(0.39f, 0.58f, 0.93f, 1.f);
		// Clear color buffer
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		// Update window with OpenGL rendering
		SDL_GL_SwapWindow(window);
	}

	//Destroy window
	SDL_DestroyWindow(window);
	window = NULL;

	//Quit SDL subsystems
	SDL_Quit();

	return 0;
}