Added a simple GLSL example using SDL
authorSam Lantinga <slouken@libsdl.org>
Tue, 08 Feb 2011 22:11:16 -0800
changeset 5232 74bc160186a8
parent 5231 e82908c86c9c
child 5233 ce4f91138031
Added a simple GLSL example using SDL
test/Makefile.in
test/testshader.c
--- a/test/Makefile.in	Tue Feb 08 20:31:39 2011 -0800
+++ b/test/Makefile.in	Tue Feb 08 22:11:16 2011 -0800
@@ -7,7 +7,56 @@
 CFLAGS  = @CFLAGS@
 LIBS	= @LIBS@
 
-TARGETS = checkkeys$(EXE) graywin$(EXE) loopwave$(EXE) testalpha$(EXE) testatomic$(EXE) testaudioinfo$(EXE) testbitmap$(EXE) testblitspeed$(EXE) testcursor$(EXE) testdraw2$(EXE) testdyngles$(EXE) testdyngl$(EXE) testerror$(EXE) testfile$(EXE) testfill$(EXE) testgamma$(EXE) testgl2$(EXE) testgles$(EXE) testgl$(EXE) testhaptic$(EXE) testhread$(EXE) testiconv$(EXE) testime$(EXE) testintersections$(EXE) testjoystick$(EXE) testkeys$(EXE) testloadso$(EXE) testlock$(EXE) testmultiaudio$(EXE) testoverlay2$(EXE) testoverlay$(EXE) testplatform$(EXE) testpower$(EXE) testresample$(EXE) testsem$(EXE) testshape$(EXE) testsprite2$(EXE) testsprite$(EXE) testspriteminimal$(EXE) testtimer$(EXE) testver$(EXE) testvidinfo$(EXE) testwin$(EXE) testwm2$(EXE) testwm$(EXE) threadwin$(EXE) torturethread$(EXE) testgesture$(EXE)
+TARGETS = \
+	checkkeys$(EXE) \
+	graywin$(EXE) \
+	loopwave$(EXE) \
+	testalpha$(EXE) \
+	testatomic$(EXE) \
+	testaudioinfo$(EXE) \
+	testbitmap$(EXE) \
+	testblitspeed$(EXE) \
+	testcursor$(EXE) \
+	testdraw2$(EXE) \
+	testdyngl$(EXE) \
+	testdyngles$(EXE) \
+	testerror$(EXE) \
+	testfile$(EXE) \
+	testfill$(EXE) \
+	testgamma$(EXE) \
+	testgesture$(EXE) \
+	testgl$(EXE) \
+	testgl2$(EXE) \
+	testgles$(EXE) \
+	testhaptic$(EXE) \
+	testhread$(EXE) \
+	testiconv$(EXE) \
+	testime$(EXE) \
+	testintersections$(EXE) \
+	testjoystick$(EXE) \
+	testkeys$(EXE) \
+	testloadso$(EXE) \
+	testlock$(EXE) \
+	testmultiaudio$(EXE) \
+	testoverlay$(EXE) \
+	testoverlay2$(EXE) \
+	testplatform$(EXE) \
+	testpower$(EXE) \
+	testresample$(EXE) \
+	testsem$(EXE) \
+	testshader$(EXE) \
+	testshape$(EXE) \
+	testsprite$(EXE) \
+	testsprite2$(EXE) \
+	testspriteminimal$(EXE) \
+	testtimer$(EXE) \
+	testver$(EXE) \
+	testvidinfo$(EXE) \
+	testwin$(EXE) \
+	testwm$(EXE) \
+	testwm2$(EXE) \
+	threadwin$(EXE) \
+	torturethread$(EXE) \
 
 all: Makefile $(TARGETS)
 
@@ -107,6 +156,9 @@
 testsem$(EXE): $(srcdir)/testsem.c
 	$(CC) -o $@ $? $(CFLAGS) $(LIBS)
 
+testshader$(EXE): $(srcdir)/testshader.c
+	$(CC) -o $@ $(srcdir)/testshader.c $(CFLAGS) $(LIBS) @GLLIB@ @MATHLIB@
+
 testshape$(EXE): $(srcdir)/testshape.c
 	$(CC) -o $@ $? -std=c99 $(CFLAGS) $(LIBS)
 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/testshader.c	Tue Feb 08 22:11:16 2011 -0800
@@ -0,0 +1,483 @@
+/* This is a simple example of using GLSL shaders with SDL */
+
+#include "SDL.h"
+
+#ifdef HAVE_OPENGL
+
+#include "SDL_opengl.h"
+
+
+static SDL_bool shaders_supported;
+static int      current_shader = 0;
+
+enum {
+    SHADER_COLOR,
+    SHADER_TEXTURE,
+    SHADER_TEXCOORDS,
+    NUM_SHADERS
+};
+
+typedef struct {
+    GLuint program;
+    GLuint vert_shader;
+    GLuint frag_shader;
+    const char *vert_source;
+    const char *frag_source;
+} ShaderData;
+
+static ShaderData shaders[NUM_SHADERS] = {
+
+    /* SHADER_COLOR */
+    { 0, 0, 0,
+        /* vertex shader */
+"varying vec4 v_color;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+"    v_color = gl_Color;\n"
+"}",
+        /* fragment shader */
+"varying vec4 v_color;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    gl_FragColor = v_color;\n"
+"}"
+    },
+
+    /* SHADER_TEXTURE */
+    { 0, 0, 0,
+        /* vertex shader */
+"varying vec4 v_color;\n"
+"varying vec2 v_texCoord;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+"    v_color = gl_Color;\n"
+"    v_texCoord = vec2(gl_MultiTexCoord0);\n"
+"}",
+        /* fragment shader */
+"varying vec4 v_color;\n"
+"varying vec2 v_texCoord;\n"
+"uniform sampler2D tex0;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
+"}"
+    },
+
+    /* SHADER_TEXCOORDS */
+    { 0, 0, 0,
+        /* vertex shader */
+"varying vec2 v_texCoord;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+"    v_texCoord = vec2(gl_MultiTexCoord0);\n"
+"}",
+        /* fragment shader */
+"varying vec2 v_texCoord;\n"
+"\n"
+"void main()\n"
+"{\n"
+"    vec4 color;\n"
+"    vec2 delta;\n"
+"    float dist;\n"
+"\n"
+"    delta = vec2(0.5, 0.5) - v_texCoord;\n"
+"    dist = dot(delta, delta);\n"
+"\n"
+"    color.r = v_texCoord.x;\n"
+"    color.g = v_texCoord.x * v_texCoord.y;\n"
+"    color.b = v_texCoord.y;\n"
+"    color.a = 1.0 - (dist * 4.0);\n"
+"    gl_FragColor = color;\n"
+"}"
+    },
+};
+    
+static PFNGLATTACHOBJECTARBPROC glAttachObjectARB;
+static PFNGLCOMPILESHADERARBPROC glCompileShaderARB;
+static PFNGLCREATEPROGRAMOBJECTARBPROC glCreateProgramObjectARB;
+static PFNGLCREATESHADEROBJECTARBPROC glCreateShaderObjectARB;
+static PFNGLDELETEOBJECTARBPROC glDeleteObjectARB;
+static PFNGLGETINFOLOGARBPROC glGetInfoLogARB;
+static PFNGLGETOBJECTPARAMETERIVARBPROC glGetObjectParameterivARB;
+static PFNGLGETUNIFORMLOCATIONARBPROC glGetUniformLocationARB;
+static PFNGLLINKPROGRAMARBPROC glLinkProgramARB;
+static PFNGLSHADERSOURCEARBPROC glShaderSourceARB;
+static PFNGLUNIFORM1IARBPROC glUniform1iARB;
+static PFNGLUSEPROGRAMOBJECTARBPROC glUseProgramObjectARB;
+
+static SDL_bool CompileShader(GLenum shader, const char *source)
+{
+    GLint status;
+
+    glShaderSourceARB(shader, 1, &source, NULL);
+    glCompileShaderARB(shader);
+    glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
+    if (status == 0) {
+        GLint length;
+        char *info;
+
+        glGetObjectParameterivARB(shader, GL_OBJECT_INFO_LOG_LENGTH_ARB, &length);
+        info = SDL_stack_alloc(char, length+1);
+        glGetInfoLogARB(shader, length, NULL, info);
+        fprintf(stderr, "Failed to compile shader:\n%s\n%s", source, info);
+        SDL_stack_free(info);
+
+        return SDL_FALSE;
+    } else {
+        return SDL_TRUE;
+    }
+}
+
+static SDL_bool CompileShaderProgram(ShaderData *data)
+{
+    const int num_tmus_bound = 4;
+    int i;
+    GLint location;
+
+    glGetError();
+
+    /* Create one program object to rule them all */
+    data->program = glCreateProgramObjectARB();
+
+    /* Create the vertex shader */
+    data->vert_shader = glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
+    if (!CompileShader(data->vert_shader, data->vert_source)) {
+        return SDL_FALSE;
+    }
+
+    /* Create the fragment shader */
+    data->frag_shader = glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
+    if (!CompileShader(data->frag_shader, data->frag_source)) {
+        return SDL_FALSE;
+    }
+
+    /* ... and in the darkness bind them */
+    glAttachObjectARB(data->program, data->vert_shader);
+    glAttachObjectARB(data->program, data->frag_shader);
+    glLinkProgramARB(data->program);
+
+    /* Set up some uniform variables */
+    glUseProgramObjectARB(data->program);
+    for (i = 0; i < num_tmus_bound; ++i) {
+        char tex_name[5];
+        SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
+        location = glGetUniformLocationARB(data->program, tex_name);
+        if (location >= 0) {
+            glUniform1iARB(location, i);
+        }
+    }
+    glUseProgramObjectARB(0);
+ 
+    return (glGetError() == GL_NO_ERROR);
+}
+
+static void DestroyShaderProgram(ShaderData *data)
+{
+    glDeleteObjectARB(data->vert_shader);
+    glDeleteObjectARB(data->frag_shader);
+    glDeleteObjectARB(data->program);
+}
+
+static SDL_bool InitShaders()
+{
+    int i;
+
+    /* Check for shader support */
+    shaders_supported = SDL_FALSE;
+    if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
+        SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
+        SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
+        SDL_GL_ExtensionSupported("GL_ARB_fragment_shader")) {
+        glAttachObjectARB = (PFNGLATTACHOBJECTARBPROC) SDL_GL_GetProcAddress("glAttachObjectARB");
+        glCompileShaderARB = (PFNGLCOMPILESHADERARBPROC) SDL_GL_GetProcAddress("glCompileShaderARB");
+        glCreateProgramObjectARB = (PFNGLCREATEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glCreateProgramObjectARB");
+        glCreateShaderObjectARB = (PFNGLCREATESHADEROBJECTARBPROC) SDL_GL_GetProcAddress("glCreateShaderObjectARB");
+        glDeleteObjectARB = (PFNGLDELETEOBJECTARBPROC) SDL_GL_GetProcAddress("glDeleteObjectARB");
+        glGetInfoLogARB = (PFNGLGETINFOLOGARBPROC) SDL_GL_GetProcAddress("glGetInfoLogARB");
+        glGetObjectParameterivARB = (PFNGLGETOBJECTPARAMETERIVARBPROC) SDL_GL_GetProcAddress("glGetObjectParameterivARB");
+        glGetUniformLocationARB = (PFNGLGETUNIFORMLOCATIONARBPROC) SDL_GL_GetProcAddress("glGetUniformLocationARB");
+        glLinkProgramARB = (PFNGLLINKPROGRAMARBPROC) SDL_GL_GetProcAddress("glLinkProgramARB");
+        glShaderSourceARB = (PFNGLSHADERSOURCEARBPROC) SDL_GL_GetProcAddress("glShaderSourceARB");
+        glUniform1iARB = (PFNGLUNIFORM1IARBPROC) SDL_GL_GetProcAddress("glUniform1iARB");
+        glUseProgramObjectARB = (PFNGLUSEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glUseProgramObjectARB");
+        if (glAttachObjectARB &&
+            glCompileShaderARB &&
+            glCreateProgramObjectARB &&
+            glCreateShaderObjectARB &&
+            glDeleteObjectARB &&
+            glGetInfoLogARB &&
+            glGetObjectParameterivARB &&
+            glGetUniformLocationARB &&
+            glLinkProgramARB &&
+            glShaderSourceARB &&
+            glUniform1iARB &&
+            glUseProgramObjectARB) {
+            shaders_supported = SDL_TRUE;
+        }
+    }
+
+    if (!shaders_supported) {
+        return SDL_FALSE;
+    }
+
+    /* Compile all the shaders */
+    for (i = 0; i < NUM_SHADERS; ++i) {
+        if (!CompileShaderProgram(&shaders[i])) {
+            fprintf(stderr, "Unable to compile shader!\n");
+            return SDL_FALSE;
+        }
+    }
+
+    /* We're done! */
+    return SDL_TRUE;
+}
+
+static void QuitShaders()
+{
+    int i;
+
+    for (i = 0; i < NUM_SHADERS; ++i) {
+        DestroyShaderProgram(&shaders[i]);
+    }
+}
+
+/* Quick utility function for texture creation */
+static int
+power_of_two(int input)
+{
+    int value = 1;
+
+    while (value < input) {
+        value <<= 1;
+    }
+    return value;
+}
+
+GLuint
+SDL_GL_LoadTexture(SDL_Surface * surface, GLfloat * texcoord)
+{
+    GLuint texture;
+    int w, h;
+    SDL_Surface *image;
+    SDL_Rect area;
+    Uint32 saved_flags;
+    Uint8 saved_alpha;
+
+    /* Use the surface width and height expanded to powers of 2 */
+    w = power_of_two(surface->w);
+    h = power_of_two(surface->h);
+    texcoord[0] = 0.0f;         /* Min X */
+    texcoord[1] = 0.0f;         /* Min Y */
+    texcoord[2] = (GLfloat) surface->w / w;     /* Max X */
+    texcoord[3] = (GLfloat) surface->h / h;     /* Max Y */
+
+    image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 32,
+#if SDL_BYTEORDER == SDL_LIL_ENDIAN     /* OpenGL RGBA masks */
+                                 0x000000FF,
+                                 0x0000FF00, 0x00FF0000, 0xFF000000
+#else
+                                 0xFF000000,
+                                 0x00FF0000, 0x0000FF00, 0x000000FF
+#endif
+        );
+    if (image == NULL) {
+        return 0;
+    }
+
+    /* Save the alpha blending attributes */
+    saved_flags = surface->flags & (SDL_SRCALPHA | SDL_RLEACCELOK);
+    SDL_GetSurfaceAlphaMod(surface, &saved_alpha);
+    if ((saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA) {
+        SDL_SetAlpha(surface, 0, 0);
+    }
+
+    /* Copy the surface into the GL texture image */
+    area.x = 0;
+    area.y = 0;
+    area.w = surface->w;
+    area.h = surface->h;
+    SDL_BlitSurface(surface, &area, image, &area);
+
+    /* Restore the alpha blending attributes */
+    if ((saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA) {
+        SDL_SetAlpha(surface, saved_flags, saved_alpha);
+    }
+
+    /* Create an OpenGL texture for the image */
+    glGenTextures(1, &texture);
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexImage2D(GL_TEXTURE_2D,
+                 0,
+                 GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
+    SDL_FreeSurface(image);     /* No longer needed */
+
+    return texture;
+}
+
+/* A general OpenGL initialization function.    Sets all of the initial parameters. */
+void InitGL(int Width, int Height)                    // We call this right after our OpenGL window is created.
+{
+    GLdouble aspect;
+
+    glViewport(0, 0, Width, Height);
+    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);        // This Will Clear The Background Color To Black
+    glClearDepth(1.0);                // Enables Clearing Of The Depth Buffer
+    glDepthFunc(GL_LESS);                // The Type Of Depth Test To Do
+    glEnable(GL_DEPTH_TEST);            // Enables Depth Testing
+    glShadeModel(GL_SMOOTH);            // Enables Smooth Color Shading
+
+    glMatrixMode(GL_PROJECTION);
+    glLoadIdentity();                // Reset The Projection Matrix
+
+    aspect = (GLdouble)Width / Height;
+    glOrtho(-3.0, 3.0, -3.0 / aspect, 3.0 / aspect, 0.0, 1.0);
+
+    glMatrixMode(GL_MODELVIEW);
+}
+
+/* The main drawing function. */
+void DrawGLScene(GLuint texture, GLfloat * texcoord)
+{
+    /* Texture coordinate lookup, to make it simple */
+    enum {
+        MINX,
+        MINY,
+        MAXX,
+        MAXY
+    };
+
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);        // Clear The Screen And The Depth Buffer
+    glLoadIdentity();                // Reset The View
+
+    glTranslatef(-1.5f,0.0f,0.0f);        // Move Left 1.5 Units
+    
+    // draw a triangle (in smooth coloring mode)
+    glBegin(GL_POLYGON);                // start drawing a polygon
+    glColor3f(1.0f,0.0f,0.0f);            // Set The Color To Red
+    glVertex3f( 0.0f, 1.0f, 0.0f);        // Top
+    glColor3f(0.0f,1.0f,0.0f);            // Set The Color To Green
+    glVertex3f( 1.0f,-1.0f, 0.0f);        // Bottom Right
+    glColor3f(0.0f,0.0f,1.0f);            // Set The Color To Blue
+    glVertex3f(-1.0f,-1.0f, 0.0f);        // Bottom Left    
+    glEnd();                    // we're done with the polygon (smooth color interpolation)    
+
+    glTranslatef(3.0f,0.0f,0.0f);         // Move Right 3 Units
+
+    // Enable blending
+    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+    // draw a textured square (quadrilateral)
+    glEnable(GL_TEXTURE_2D);
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glColor3f(1.0f,1.0f,1.0f);
+    if (shaders_supported) {
+        glUseProgramObjectARB(shaders[current_shader].program);
+    }
+
+    glBegin(GL_QUADS);                // start drawing a polygon (4 sided)
+    glTexCoord2f(texcoord[MINX], texcoord[MINY]);
+    glVertex3f(-1.0f, 1.0f, 0.0f);        // Top Left
+    glTexCoord2f(texcoord[MAXX], texcoord[MINY]);
+    glVertex3f( 1.0f, 1.0f, 0.0f);        // Top Right
+    glTexCoord2f(texcoord[MAXX], texcoord[MAXY]);
+    glVertex3f( 1.0f,-1.0f, 0.0f);        // Bottom Right
+    glTexCoord2f(texcoord[MINX], texcoord[MAXY]);
+    glVertex3f(-1.0f,-1.0f, 0.0f);        // Bottom Left    
+    glEnd();                    // done with the polygon
+
+    if (shaders_supported) {
+        glUseProgramObjectARB(0);
+    }
+    glDisable(GL_TEXTURE_2D);
+
+    // swap buffers to display, since we're double buffered.
+    SDL_GL_SwapBuffers();
+}
+
+int main(int argc, char **argv) 
+{    
+    int done;
+    SDL_Surface *surface;
+    GLuint texture;
+    GLfloat texcoords[4];
+
+    /* Initialize SDL for video output */
+    if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
+        fprintf(stderr, "Unable to initialize SDL: %s\n", SDL_GetError());
+        exit(1);
+    }
+
+    /* Create a 640x480 OpenGL screen */
+    if ( SDL_SetVideoMode(640, 480, 0, SDL_OPENGL) == NULL ) {
+        fprintf(stderr, "Unable to create OpenGL screen: %s\n", SDL_GetError());
+        SDL_Quit();
+        exit(2);
+    }
+
+    /* Set the title bar in environments that support it */
+    SDL_WM_SetCaption("Shader Demo", NULL);
+
+    surface = SDL_LoadBMP("icon.bmp");
+    if ( ! surface ) {
+        fprintf(stderr, "Unable to load icon.bmp: %s\n", SDL_GetError());
+        SDL_Quit();
+        exit(3);
+    }
+    texture = SDL_GL_LoadTexture(surface, texcoords);
+    SDL_FreeSurface(surface);
+
+    /* Loop, drawing and checking events */
+    InitGL(640, 480);
+    if (InitShaders()) {
+        printf("Shaders supported, press SPACE to cycle them.\n");
+    } else {
+        printf("Shaders not supported!\n");
+    }
+    done = 0;
+    while ( ! done ) {
+        DrawGLScene(texture, texcoords);
+
+        /* This could go in a separate function */
+        { SDL_Event event;
+            while ( SDL_PollEvent(&event) ) {
+                if ( event.type == SDL_QUIT ) {
+                    done = 1;
+                }
+                if ( event.type == SDL_KEYDOWN ) {
+                    if ( event.key.keysym.sym == SDLK_SPACE ) {
+                        current_shader = (current_shader + 1) % NUM_SHADERS;
+                    }
+                    if ( event.key.keysym.sym == SDLK_ESCAPE ) {
+                        done = 1;
+                    }
+                }
+            }
+        }
+    }
+    QuitShaders();
+    SDL_Quit();
+    return 1;
+}
+
+#else /* HAVE_OPENGL */
+
+int
+main(int argc, char *argv[])
+{
+    printf("No OpenGL support on this system\n");
+    return 1;
+}
+
+#endif /* HAVE_OPENGL */