/******************************************************************* * * * Using SDL With OpenGL * * * * Tutorial by Kyle Foley (sdw) * * * * http://gpwiki.org/index.php/SDL:Tutorials:Using_SDL_with_OpenGL * * * *******************************************************************/ /* THIS WORK, INCLUDING THE SOURCE CODE, DOCUMENTATION AND RELATED MEDIA AND DATA, IS PLACED INTO THE PUBLIC DOMAIN. THE ORIGINAL AUTHOR IS KYLE FOLEY. THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR REDISTRIBUTION OF THIS SOFTWARE. */ #if !EMSCRIPTEN #define USE_GLEW 1 #endif #if USE_GLEW #include "GL/glew.h" #endif #include "SDL/SDL.h" #include "SDL/SDL_image.h" #if !USE_GLEW #include "SDL/SDL_opengl.h" #endif #include #include #include void shaders() { #if USE_GLEW glewInit(); #endif GLint ok; const char *vertexShader = "void main(void) \n" "{ \n" " gl_Position = ftransform(); \n" " gl_TexCoord[0] = gl_MultiTexCoord0; \n" " gl_FrontColor = gl_Color; \n" "} \n"; const char *fragmentShader = "uniform sampler2D tex0; \n" "void main(void) \n" "{ \n" " gl_FragColor = gl_Color * texture2D(tex0, gl_TexCoord[0].xy); \n" "} \n"; GLuint vs = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vs, 1, &vertexShader, NULL); glCompileShader(vs); glGetShaderiv(vs, GL_COMPILE_STATUS, &ok); assert(ok); GLuint fs = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(fs, 1, &fragmentShader, NULL); glCompileShader(fs); glGetShaderiv(fs, GL_COMPILE_STATUS, &ok); assert(ok); GLuint program = glCreateProgram(); glAttachShader(program, vs); glAttachShader(program, fs); glLinkProgram(program); glGetProgramiv(program, GL_LINK_STATUS, &ok); assert(ok); assert(glIsProgram(program)); assert(!glIsProgram(0)); assert(!glIsProgram(program+1)); // a number that can't be a real shader glUseProgram(program); { // Also, check getting the error log const char *fakeVertexShader = "atbute ve4 blarg; ### AAA\n"; GLuint vs = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vs, 1, &fakeVertexShader, NULL); glCompileShader(vs); glGetShaderiv(vs, GL_COMPILE_STATUS, &ok); assert(!ok); GLint infoLen = 0; glGetShaderiv(vs, GL_INFO_LOG_LENGTH, &infoLen); assert(infoLen > 1); } } int main(int argc, char *argv[]) { SDL_Surface *screen; // Slightly different SDL initialization if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) { printf("Unable to initialize SDL: %s\n", SDL_GetError()); return 1; } SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new* screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL ); // *changed* if ( !screen ) { printf("Unable to set video mode: %s\n", SDL_GetError()); return 1; } // Set the OpenGL state after creating the context with SDL_SetVideoMode glClearColor( 0, 0, 0, 0 ); #if !EMSCRIPTEN glEnable( GL_TEXTURE_2D ); // Need this to display a texture XXX unnecessary in OpenGL ES 2.0/WebGL #endif glViewport( 0, 0, 640, 480 ); glMatrixMode( GL_PROJECTION ); GLfloat matrixData[] = { 2.0/640, 0, 0, 0, 0, -2.0/480, 0, 0, 0, 0, -1, 0, -1, 1, 0, 1 }; glLoadMatrixf(matrixData); // test loadmatrix glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); // Load the OpenGL texture GLuint texture; // Texture object handle SDL_Surface *surface; // Gives us the information to make the texture if ( (surface = IMG_Load("screenshot.png")) ) { // Check that the image's width is a power of 2 if ( (surface->w & (surface->w - 1)) != 0 ) { printf("warning: image.bmp's width is not a power of 2\n"); } // Also check if the height is a power of 2 if ( (surface->h & (surface->h - 1)) != 0 ) { printf("warning: image.bmp's height is not a power of 2\n"); } // Have OpenGL generate a texture object handle for us glGenTextures( 1, &texture ); // Bind the texture object glBindTexture( GL_TEXTURE_2D, texture ); // Set the texture's stretching properties glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR ); glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); //SDL_LockSurface(surface); // Add some greyness memset(surface->pixels, 0x66, surface->w*surface->h); // Edit the texture object's image data using the information SDL_Surface gives us glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, surface->w, surface->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, surface->pixels ); //SDL_UnlockSurface(surface); } else { printf("SDL could not load image.bmp: %s\n", SDL_GetError()); SDL_Quit(); return 1; } // Free the SDL_Surface only if it was successfully created if ( surface ) { SDL_FreeSurface( surface ); } // Clear the screen before drawing glClear( GL_COLOR_BUFFER_BIT ); shaders(); // Bind the texture to which subsequent calls refer to glBindTexture( GL_TEXTURE_2D, texture ); // Use clientside vertex pointers to render two items GLfloat vertexData[] = { 0, 0, 10, 10, // texture2, position2 1, 0, 300, 10, 1, 1, 300, 128, 0, 1, 10, 128, 0, 0.5, 410, 10, 1, 0.5, 600, 10, 1, 1, 630, 200, 0.5, 1, 310, 250, 0, 0, 100, 300, 1, 0, 300, 300, 1, 1, 300, 400, 0, 1, 100, 400 }; glEnableClientState(GL_TEXTURE_COORD_ARRAY); glTexCoordPointer(2, GL_FLOAT, 4*4, &vertexData[0]); glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(2, GL_FLOAT, 4*4, &vertexData[2]); glDrawArrays(GL_QUADS, 0, 12); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glDisableClientState(GL_VERTEX_ARRAY); SDL_GL_SwapBuffers(); #if !EMSCRIPTEN // Wait for 3 seconds to give us a chance to see the image SDL_Delay(3000); #endif // Now we can delete the OpenGL texture and close down SDL glDeleteTextures( 1, &texture ); SDL_Quit(); return 0; }