2 Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
4 This software is provided 'as-is', without any express or implied
5 warranty. In no event will the authors be held liable for any damages
6 arising from the use of this software.
8 Permission is granted to anyone to use this software for any purpose,
9 including commercial applications, and to alter it and redistribute it
12 /* This is a simple example of using GLSL shaders with SDL */
18 #include "SDL_opengl.h"
21 static SDL_bool shaders_supported;
22 static int current_shader = 0;
33 GLhandleARB vert_shader;
34 GLhandleARB frag_shader;
35 const char *vert_source;
36 const char *frag_source;
39 static ShaderData shaders[NUM_SHADERS] = {
44 "varying vec4 v_color;\n"
48 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
49 " v_color = gl_Color;\n"
52 "varying vec4 v_color;\n"
56 " gl_FragColor = v_color;\n"
63 "varying vec4 v_color;\n"
64 "varying vec2 v_texCoord;\n"
68 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
69 " v_color = gl_Color;\n"
70 " v_texCoord = vec2(gl_MultiTexCoord0);\n"
73 "varying vec4 v_color;\n"
74 "varying vec2 v_texCoord;\n"
75 "uniform sampler2D tex0;\n"
79 " gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
83 /* SHADER_TEXCOORDS */
86 "varying vec2 v_texCoord;\n"
90 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
91 " v_texCoord = vec2(gl_MultiTexCoord0);\n"
94 "varying vec2 v_texCoord;\n"
102 " delta = vec2(0.5, 0.5) - v_texCoord;\n"
103 " dist = dot(delta, delta);\n"
105 " color.r = v_texCoord.x;\n"
106 " color.g = v_texCoord.x * v_texCoord.y;\n"
107 " color.b = v_texCoord.y;\n"
108 " color.a = 1.0 - (dist * 4.0);\n"
109 " gl_FragColor = color;\n"
114 static PFNGLATTACHOBJECTARBPROC glAttachObjectARB;
115 static PFNGLCOMPILESHADERARBPROC glCompileShaderARB;
116 static PFNGLCREATEPROGRAMOBJECTARBPROC glCreateProgramObjectARB;
117 static PFNGLCREATESHADEROBJECTARBPROC glCreateShaderObjectARB;
118 static PFNGLDELETEOBJECTARBPROC glDeleteObjectARB;
119 static PFNGLGETINFOLOGARBPROC glGetInfoLogARB;
120 static PFNGLGETOBJECTPARAMETERIVARBPROC glGetObjectParameterivARB;
121 static PFNGLGETUNIFORMLOCATIONARBPROC glGetUniformLocationARB;
122 static PFNGLLINKPROGRAMARBPROC glLinkProgramARB;
123 static PFNGLSHADERSOURCEARBPROC glShaderSourceARB;
124 static PFNGLUNIFORM1IARBPROC glUniform1iARB;
125 static PFNGLUSEPROGRAMOBJECTARBPROC glUseProgramObjectARB;
127 static SDL_bool CompileShader(GLhandleARB shader, const char *source)
131 glShaderSourceARB(shader, 1, &source, NULL);
132 glCompileShaderARB(shader);
133 glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
138 glGetObjectParameterivARB(shader, GL_OBJECT_INFO_LOG_LENGTH_ARB, &length);
139 info = SDL_stack_alloc(char, length+1);
140 glGetInfoLogARB(shader, length, NULL, info);
141 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to compile shader:\n%s\n%s", source, info);
142 SDL_stack_free(info);
150 static SDL_bool CompileShaderProgram(ShaderData *data)
152 const int num_tmus_bound = 4;
158 /* Create one program object to rule them all */
159 data->program = glCreateProgramObjectARB();
161 /* Create the vertex shader */
162 data->vert_shader = glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
163 if (!CompileShader(data->vert_shader, data->vert_source)) {
167 /* Create the fragment shader */
168 data->frag_shader = glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
169 if (!CompileShader(data->frag_shader, data->frag_source)) {
173 /* ... and in the darkness bind them */
174 glAttachObjectARB(data->program, data->vert_shader);
175 glAttachObjectARB(data->program, data->frag_shader);
176 glLinkProgramARB(data->program);
178 /* Set up some uniform variables */
179 glUseProgramObjectARB(data->program);
180 for (i = 0; i < num_tmus_bound; ++i) {
182 SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
183 location = glGetUniformLocationARB(data->program, tex_name);
185 glUniform1iARB(location, i);
188 glUseProgramObjectARB(0);
190 return (glGetError() == GL_NO_ERROR) ? SDL_TRUE : SDL_FALSE;
193 static void DestroyShaderProgram(ShaderData *data)
195 if (shaders_supported) {
196 glDeleteObjectARB(data->vert_shader);
197 glDeleteObjectARB(data->frag_shader);
198 glDeleteObjectARB(data->program);
202 static SDL_bool InitShaders()
206 /* Check for shader support */
207 shaders_supported = SDL_FALSE;
208 if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
209 SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
210 SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
211 SDL_GL_ExtensionSupported("GL_ARB_fragment_shader")) {
212 glAttachObjectARB = (PFNGLATTACHOBJECTARBPROC) SDL_GL_GetProcAddress("glAttachObjectARB");
213 glCompileShaderARB = (PFNGLCOMPILESHADERARBPROC) SDL_GL_GetProcAddress("glCompileShaderARB");
214 glCreateProgramObjectARB = (PFNGLCREATEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glCreateProgramObjectARB");
215 glCreateShaderObjectARB = (PFNGLCREATESHADEROBJECTARBPROC) SDL_GL_GetProcAddress("glCreateShaderObjectARB");
216 glDeleteObjectARB = (PFNGLDELETEOBJECTARBPROC) SDL_GL_GetProcAddress("glDeleteObjectARB");
217 glGetInfoLogARB = (PFNGLGETINFOLOGARBPROC) SDL_GL_GetProcAddress("glGetInfoLogARB");
218 glGetObjectParameterivARB = (PFNGLGETOBJECTPARAMETERIVARBPROC) SDL_GL_GetProcAddress("glGetObjectParameterivARB");
219 glGetUniformLocationARB = (PFNGLGETUNIFORMLOCATIONARBPROC) SDL_GL_GetProcAddress("glGetUniformLocationARB");
220 glLinkProgramARB = (PFNGLLINKPROGRAMARBPROC) SDL_GL_GetProcAddress("glLinkProgramARB");
221 glShaderSourceARB = (PFNGLSHADERSOURCEARBPROC) SDL_GL_GetProcAddress("glShaderSourceARB");
222 glUniform1iARB = (PFNGLUNIFORM1IARBPROC) SDL_GL_GetProcAddress("glUniform1iARB");
223 glUseProgramObjectARB = (PFNGLUSEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glUseProgramObjectARB");
224 if (glAttachObjectARB &&
225 glCompileShaderARB &&
226 glCreateProgramObjectARB &&
227 glCreateShaderObjectARB &&
230 glGetObjectParameterivARB &&
231 glGetUniformLocationARB &&
235 glUseProgramObjectARB) {
236 shaders_supported = SDL_TRUE;
240 if (!shaders_supported) {
244 /* Compile all the shaders */
245 for (i = 0; i < NUM_SHADERS; ++i) {
246 if (!CompileShaderProgram(&shaders[i])) {
247 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to compile shader!\n");
256 static void QuitShaders()
260 for (i = 0; i < NUM_SHADERS; ++i) {
261 DestroyShaderProgram(&shaders[i]);
265 /* Quick utility function for texture creation */
267 power_of_two(int input)
271 while (value < input) {
278 SDL_GL_LoadTexture(SDL_Surface * surface, GLfloat * texcoord)
284 SDL_BlendMode saved_mode;
286 /* Use the surface width and height expanded to powers of 2 */
287 w = power_of_two(surface->w);
288 h = power_of_two(surface->h);
289 texcoord[0] = 0.0f; /* Min X */
290 texcoord[1] = 0.0f; /* Min Y */
291 texcoord[2] = (GLfloat) surface->w / w; /* Max X */
292 texcoord[3] = (GLfloat) surface->h / h; /* Max Y */
294 image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 32,
295 #if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
297 0x0000FF00, 0x00FF0000, 0xFF000000
300 0x00FF0000, 0x0000FF00, 0x000000FF
307 /* Save the alpha blending attributes */
308 SDL_GetSurfaceBlendMode(surface, &saved_mode);
309 SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE);
311 /* Copy the surface into the GL texture image */
316 SDL_BlitSurface(surface, &area, image, &area);
318 /* Restore the alpha blending attributes */
319 SDL_SetSurfaceBlendMode(surface, saved_mode);
321 /* Create an OpenGL texture for the image */
322 glGenTextures(1, &texture);
323 glBindTexture(GL_TEXTURE_2D, texture);
324 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
325 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
326 glTexImage2D(GL_TEXTURE_2D,
328 GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
329 SDL_FreeSurface(image); /* No longer needed */
334 /* A general OpenGL initialization function. Sets all of the initial parameters. */
335 void InitGL(int Width, int Height) /* We call this right after our OpenGL window is created. */
339 glViewport(0, 0, Width, Height);
340 glClearColor(0.0f, 0.0f, 0.0f, 0.0f); /* This Will Clear The Background Color To Black */
341 glClearDepth(1.0); /* Enables Clearing Of The Depth Buffer */
342 glDepthFunc(GL_LESS); /* The Type Of Depth Test To Do */
343 glEnable(GL_DEPTH_TEST); /* Enables Depth Testing */
344 glShadeModel(GL_SMOOTH); /* Enables Smooth Color Shading */
346 glMatrixMode(GL_PROJECTION);
347 glLoadIdentity(); /* Reset The Projection Matrix */
349 aspect = (GLdouble)Width / Height;
350 glOrtho(-3.0, 3.0, -3.0 / aspect, 3.0 / aspect, 0.0, 1.0);
352 glMatrixMode(GL_MODELVIEW);
355 /* The main drawing function. */
356 void DrawGLScene(SDL_Window *window, GLuint texture, GLfloat * texcoord)
358 /* Texture coordinate lookup, to make it simple */
366 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); /* Clear The Screen And The Depth Buffer */
367 glLoadIdentity(); /* Reset The View */
369 glTranslatef(-1.5f,0.0f,0.0f); /* Move Left 1.5 Units */
371 /* draw a triangle (in smooth coloring mode) */
372 glBegin(GL_POLYGON); /* start drawing a polygon */
373 glColor3f(1.0f,0.0f,0.0f); /* Set The Color To Red */
374 glVertex3f( 0.0f, 1.0f, 0.0f); /* Top */
375 glColor3f(0.0f,1.0f,0.0f); /* Set The Color To Green */
376 glVertex3f( 1.0f,-1.0f, 0.0f); /* Bottom Right */
377 glColor3f(0.0f,0.0f,1.0f); /* Set The Color To Blue */
378 glVertex3f(-1.0f,-1.0f, 0.0f); /* Bottom Left */
379 glEnd(); /* we're done with the polygon (smooth color interpolation) */
381 glTranslatef(3.0f,0.0f,0.0f); /* Move Right 3 Units */
383 /* Enable blending */
384 glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
386 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
388 /* draw a textured square (quadrilateral) */
389 glEnable(GL_TEXTURE_2D);
390 glBindTexture(GL_TEXTURE_2D, texture);
391 glColor3f(1.0f,1.0f,1.0f);
392 if (shaders_supported) {
393 glUseProgramObjectARB(shaders[current_shader].program);
396 glBegin(GL_QUADS); /* start drawing a polygon (4 sided) */
397 glTexCoord2f(texcoord[MINX], texcoord[MINY]);
398 glVertex3f(-1.0f, 1.0f, 0.0f); /* Top Left */
399 glTexCoord2f(texcoord[MAXX], texcoord[MINY]);
400 glVertex3f( 1.0f, 1.0f, 0.0f); /* Top Right */
401 glTexCoord2f(texcoord[MAXX], texcoord[MAXY]);
402 glVertex3f( 1.0f,-1.0f, 0.0f); /* Bottom Right */
403 glTexCoord2f(texcoord[MINX], texcoord[MAXY]);
404 glVertex3f(-1.0f,-1.0f, 0.0f); /* Bottom Left */
405 glEnd(); /* done with the polygon */
407 if (shaders_supported) {
408 glUseProgramObjectARB(0);
410 glDisable(GL_TEXTURE_2D);
412 /* swap buffers to display, since we're double buffered. */
413 SDL_GL_SwapWindow(window);
416 int main(int argc, char **argv)
420 SDL_Surface *surface;
422 GLfloat texcoords[4];
424 /* Enable standard application logging */
425 SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
427 /* Initialize SDL for video output */
428 if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
429 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to initialize SDL: %s\n", SDL_GetError());
433 /* Create a 640x480 OpenGL screen */
434 window = SDL_CreateWindow( "Shader Demo", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL );
436 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL window: %s\n", SDL_GetError());
441 if ( !SDL_GL_CreateContext(window)) {
442 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL context: %s\n", SDL_GetError());
447 surface = SDL_LoadBMP("icon.bmp");
449 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to load icon.bmp: %s\n", SDL_GetError());
453 texture = SDL_GL_LoadTexture(surface, texcoords);
454 SDL_FreeSurface(surface);
456 /* Loop, drawing and checking events */
459 SDL_Log("Shaders supported, press SPACE to cycle them.\n");
461 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Shaders not supported!\n");
465 DrawGLScene(window, texture, texcoords);
467 /* This could go in a separate function */
469 while ( SDL_PollEvent(&event) ) {
470 if ( event.type == SDL_QUIT ) {
473 if ( event.type == SDL_KEYDOWN ) {
474 if ( event.key.keysym.sym == SDLK_SPACE ) {
475 current_shader = (current_shader + 1) % NUM_SHADERS;
477 if ( event.key.keysym.sym == SDLK_ESCAPE ) {
489 #else /* HAVE_OPENGL */
492 main(int argc, char *argv[])
494 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "No OpenGL support on this system\n");
498 #endif /* HAVE_OPENGL */
500 /* vi: set ts=4 sw=4 expandtab: */