1 /*
2 Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
3
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.
7
8 Permission is granted to anyone to use this software for any purpose,
9 including commercial applications, and to alter it and redistribute it
10 freely.
11 */
12 /* This is a simple example of using GLSL shaders with SDL */
13
14 #include "SDL.h"
15
16 #ifdef HAVE_OPENGL
17
18 #include "SDL_opengl.h"
19
20
21 static SDL_bool shaders_supported;
22 static int current_shader = 0;
23
24 enum {
25 SHADER_COLOR,
26 SHADER_TEXTURE,
27 SHADER_TEXCOORDS,
28 NUM_SHADERS
29 };
30
31 typedef struct {
32 GLhandleARB program;
33 GLhandleARB vert_shader;
34 GLhandleARB frag_shader;
35 const char *vert_source;
36 const char *frag_source;
37 } ShaderData;
38
39 static ShaderData shaders[NUM_SHADERS] = {
40
41 /* SHADER_COLOR */
42 { 0, 0, 0,
43 /* vertex shader */
44 "varying vec4 v_color;\n"
45 "\n"
46 "void main()\n"
47 "{\n"
48 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
49 " v_color = gl_Color;\n"
50 "}",
51 /* fragment shader */
52 "varying vec4 v_color;\n"
53 "\n"
54 "void main()\n"
55 "{\n"
56 " gl_FragColor = v_color;\n"
57 "}"
58 },
59
60 /* SHADER_TEXTURE */
61 { 0, 0, 0,
62 /* vertex shader */
63 "varying vec4 v_color;\n"
64 "varying vec2 v_texCoord;\n"
65 "\n"
66 "void main()\n"
67 "{\n"
68 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
69 " v_color = gl_Color;\n"
70 " v_texCoord = vec2(gl_MultiTexCoord0);\n"
71 "}",
72 /* fragment shader */
73 "varying vec4 v_color;\n"
74 "varying vec2 v_texCoord;\n"
75 "uniform sampler2D tex0;\n"
76 "\n"
77 "void main()\n"
78 "{\n"
79 " gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
80 "}"
81 },
82
83 /* SHADER_TEXCOORDS */
84 { 0, 0, 0,
85 /* vertex shader */
86 "varying vec2 v_texCoord;\n"
87 "\n"
88 "void main()\n"
89 "{\n"
90 " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
91 " v_texCoord = vec2(gl_MultiTexCoord0);\n"
92 "}",
93 /* fragment shader */
94 "varying vec2 v_texCoord;\n"
95 "\n"
96 "void main()\n"
97 "{\n"
98 " vec4 color;\n"
99 " vec2 delta;\n"
100 " float dist;\n"
101 "\n"
102 " delta = vec2(0.5, 0.5) - v_texCoord;\n"
103 " dist = dot(delta, delta);\n"
104 "\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"
110 "}"
111 },
112 };
113
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;
126
CompileShader(GLhandleARB shader,const char * source)127 static SDL_bool CompileShader(GLhandleARB shader, const char *source)
128 {
129 GLint status;
130
131 glShaderSourceARB(shader, 1, &source, NULL);
132 glCompileShaderARB(shader);
133 glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
134 if (status == 0) {
135 GLint length;
136 char *info;
137
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);
143
144 return SDL_FALSE;
145 } else {
146 return SDL_TRUE;
147 }
148 }
149
CompileShaderProgram(ShaderData * data)150 static SDL_bool CompileShaderProgram(ShaderData *data)
151 {
152 const int num_tmus_bound = 4;
153 int i;
154 GLint location;
155
156 glGetError();
157
158 /* Create one program object to rule them all */
159 data->program = glCreateProgramObjectARB();
160
161 /* Create the vertex shader */
162 data->vert_shader = glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
163 if (!CompileShader(data->vert_shader, data->vert_source)) {
164 return SDL_FALSE;
165 }
166
167 /* Create the fragment shader */
168 data->frag_shader = glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
169 if (!CompileShader(data->frag_shader, data->frag_source)) {
170 return SDL_FALSE;
171 }
172
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);
177
178 /* Set up some uniform variables */
179 glUseProgramObjectARB(data->program);
180 for (i = 0; i < num_tmus_bound; ++i) {
181 char tex_name[5];
182 SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
183 location = glGetUniformLocationARB(data->program, tex_name);
184 if (location >= 0) {
185 glUniform1iARB(location, i);
186 }
187 }
188 glUseProgramObjectARB(0);
189
190 return (glGetError() == GL_NO_ERROR) ? SDL_TRUE : SDL_FALSE;
191 }
192
DestroyShaderProgram(ShaderData * data)193 static void DestroyShaderProgram(ShaderData *data)
194 {
195 if (shaders_supported) {
196 glDeleteObjectARB(data->vert_shader);
197 glDeleteObjectARB(data->frag_shader);
198 glDeleteObjectARB(data->program);
199 }
200 }
201
InitShaders()202 static SDL_bool InitShaders()
203 {
204 int i;
205
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 &&
228 glDeleteObjectARB &&
229 glGetInfoLogARB &&
230 glGetObjectParameterivARB &&
231 glGetUniformLocationARB &&
232 glLinkProgramARB &&
233 glShaderSourceARB &&
234 glUniform1iARB &&
235 glUseProgramObjectARB) {
236 shaders_supported = SDL_TRUE;
237 }
238 }
239
240 if (!shaders_supported) {
241 return SDL_FALSE;
242 }
243
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");
248 return SDL_FALSE;
249 }
250 }
251
252 /* We're done! */
253 return SDL_TRUE;
254 }
255
QuitShaders()256 static void QuitShaders()
257 {
258 int i;
259
260 for (i = 0; i < NUM_SHADERS; ++i) {
261 DestroyShaderProgram(&shaders[i]);
262 }
263 }
264
265 /* Quick utility function for texture creation */
266 static int
power_of_two(int input)267 power_of_two(int input)
268 {
269 int value = 1;
270
271 while (value < input) {
272 value <<= 1;
273 }
274 return value;
275 }
276
277 GLuint
SDL_GL_LoadTexture(SDL_Surface * surface,GLfloat * texcoord)278 SDL_GL_LoadTexture(SDL_Surface * surface, GLfloat * texcoord)
279 {
280 GLuint texture;
281 int w, h;
282 SDL_Surface *image;
283 SDL_Rect area;
284 SDL_BlendMode saved_mode;
285
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 */
293
294 image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 32,
295 #if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
296 0x000000FF,
297 0x0000FF00, 0x00FF0000, 0xFF000000
298 #else
299 0xFF000000,
300 0x00FF0000, 0x0000FF00, 0x000000FF
301 #endif
302 );
303 if (image == NULL) {
304 return 0;
305 }
306
307 /* Save the alpha blending attributes */
308 SDL_GetSurfaceBlendMode(surface, &saved_mode);
309 SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE);
310
311 /* Copy the surface into the GL texture image */
312 area.x = 0;
313 area.y = 0;
314 area.w = surface->w;
315 area.h = surface->h;
316 SDL_BlitSurface(surface, &area, image, &area);
317
318 /* Restore the alpha blending attributes */
319 SDL_SetSurfaceBlendMode(surface, saved_mode);
320
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,
327 0,
328 GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
329 SDL_FreeSurface(image); /* No longer needed */
330
331 return texture;
332 }
333
334 /* A general OpenGL initialization function. Sets all of the initial parameters. */
InitGL(int Width,int Height)335 void InitGL(int Width, int Height) /* We call this right after our OpenGL window is created. */
336 {
337 GLdouble aspect;
338
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 */
345
346 glMatrixMode(GL_PROJECTION);
347 glLoadIdentity(); /* Reset The Projection Matrix */
348
349 aspect = (GLdouble)Width / Height;
350 glOrtho(-3.0, 3.0, -3.0 / aspect, 3.0 / aspect, 0.0, 1.0);
351
352 glMatrixMode(GL_MODELVIEW);
353 }
354
355 /* The main drawing function. */
DrawGLScene(SDL_Window * window,GLuint texture,GLfloat * texcoord)356 void DrawGLScene(SDL_Window *window, GLuint texture, GLfloat * texcoord)
357 {
358 /* Texture coordinate lookup, to make it simple */
359 enum {
360 MINX,
361 MINY,
362 MAXX,
363 MAXY
364 };
365
366 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); /* Clear The Screen And The Depth Buffer */
367 glLoadIdentity(); /* Reset The View */
368
369 glTranslatef(-1.5f,0.0f,0.0f); /* Move Left 1.5 Units */
370
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) */
380
381 glTranslatef(3.0f,0.0f,0.0f); /* Move Right 3 Units */
382
383 /* Enable blending */
384 glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
385 glEnable(GL_BLEND);
386 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
387
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);
394 }
395
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 */
406
407 if (shaders_supported) {
408 glUseProgramObjectARB(0);
409 }
410 glDisable(GL_TEXTURE_2D);
411
412 /* swap buffers to display, since we're double buffered. */
413 SDL_GL_SwapWindow(window);
414 }
415
main(int argc,char ** argv)416 int main(int argc, char **argv)
417 {
418 int done;
419 SDL_Window *window;
420 SDL_Surface *surface;
421 GLuint texture;
422 GLfloat texcoords[4];
423
424 /* Enable standard application logging */
425 SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
426
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());
430 exit(1);
431 }
432
433 /* Create a 640x480 OpenGL screen */
434 window = SDL_CreateWindow( "Shader Demo", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL );
435 if ( !window ) {
436 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL window: %s\n", SDL_GetError());
437 SDL_Quit();
438 exit(2);
439 }
440
441 if ( !SDL_GL_CreateContext(window)) {
442 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to create OpenGL context: %s\n", SDL_GetError());
443 SDL_Quit();
444 exit(2);
445 }
446
447 surface = SDL_LoadBMP("icon.bmp");
448 if ( ! surface ) {
449 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to load icon.bmp: %s\n", SDL_GetError());
450 SDL_Quit();
451 exit(3);
452 }
453 texture = SDL_GL_LoadTexture(surface, texcoords);
454 SDL_FreeSurface(surface);
455
456 /* Loop, drawing and checking events */
457 InitGL(640, 480);
458 if (InitShaders()) {
459 SDL_Log("Shaders supported, press SPACE to cycle them.\n");
460 } else {
461 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Shaders not supported!\n");
462 }
463 done = 0;
464 while ( ! done ) {
465 DrawGLScene(window, texture, texcoords);
466
467 /* This could go in a separate function */
468 { SDL_Event event;
469 while ( SDL_PollEvent(&event) ) {
470 if ( event.type == SDL_QUIT ) {
471 done = 1;
472 }
473 if ( event.type == SDL_KEYDOWN ) {
474 if ( event.key.keysym.sym == SDLK_SPACE ) {
475 current_shader = (current_shader + 1) % NUM_SHADERS;
476 }
477 if ( event.key.keysym.sym == SDLK_ESCAPE ) {
478 done = 1;
479 }
480 }
481 }
482 }
483 }
484 QuitShaders();
485 SDL_Quit();
486 return 1;
487 }
488
489 #else /* HAVE_OPENGL */
490
491 int
main(int argc,char * argv[])492 main(int argc, char *argv[])
493 {
494 SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "No OpenGL support on this system\n");
495 return 1;
496 }
497
498 #endif /* HAVE_OPENGL */
499
500 /* vi: set ts=4 sw=4 expandtab: */
501