Implement GL_LINEAR fog mode

1 files changed, 185 insertions, 0 deletions

diff --git a/tests/sdl_fog_linear.c b/tests/sdl_fog_linear.c
new file mode 100644
index 00000000..8fc18b7c
--- /dev/null
+++ b/tests/sdl_fog_linear.c
@@ -0,0 +1,185 @@
+/*******************************************************************
+ *                                                                 *
+ *                        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.
+*/
+
+#include "SDL/SDL.h"
+#include "SDL/SDL_image.h"
+#include "SDL/SDL_opengl.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+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 );
+    glPushMatrix(); // just for testing
+    glLoadIdentity();
+
+    glOrtho( 0, 640, 480, 0, -1000, 1000 );
+    
+    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 );
+    
+    // Bind the texture to which subsequent calls refer to
+    glBindTexture( GL_TEXTURE_2D, texture );
+
+    glEnable(GL_FOG);
+    GLfloat fogColor[] = { 1.0, 0.5, 0.5, 0.05 };
+    glFogfv(GL_FOG_COLOR, fogColor);
+    glFogi(GL_FOG_START, 8);
+    glFogi(GL_FOG_END, 13);
+    glFogi(GL_FOG_MODE, GL_LINEAR);
+
+    assert(glIsEnabled(GL_FOG));
+
+    glBegin( GL_QUADS );
+        glTexCoord2i( 0, 0 ); glVertex3f( 10, 10, 10 );
+        glTexCoord2i( 1, 0 ); glVertex3f( 300, 10, 10 );
+        glTexCoord2i( 1, 1 ); glVertex3f( 300, 128, 10 );
+        glTexCoord2i( 0, 1 ); glVertex3f( 10, 128, 10 );
+
+        glTexCoord2f( 0, 0.5 ); glVertex3f( 410, 10, 5 );
+        glTexCoord2f( 1, 0.5 ); glVertex3f( 600, 10, 6 );
+        glTexCoord2f( 1, 1   ); glVertex3f( 630, 200, 7 );
+        glTexCoord2f( 0.5, 1 ); glVertex3f( 310, 250, 8 );
+    glEnd();
+
+    glBegin( GL_TRIANGLE_STRIP );
+        glTexCoord2i( 0, 0 ); glVertex3f( 100, 300, 1 );
+        glTexCoord2i( 1, 0 ); glVertex3f( 300, 300, 1 );
+        glTexCoord2i( 1, 1 ); glVertex3f( 300, 400, 1 );
+        glTexCoord2i( 0, 1 ); glVertex3f( 500, 410, 1 );
+    glEnd();
+
+#if !EMSCRIPTEN
+    glDisable(GL_TEXTURE_2D);
+#endif
+
+    glColor3ub(90, 255, 255);
+    glBegin( GL_QUADS );
+        glVertex3f( 10, 410, 5 );
+        glVertex3f( 300, 410, 50 );
+        glVertex3f( 300, 480, 100 );
+        glVertex3f( 10, 470, 5 );
+    glEnd();
+
+    glBegin( GL_QUADS );
+        glColor3f(1.0, 0, 1.0);   glVertex3f( 410, 410, 10 );
+        glColor3f(0, 1.0, 0);     glVertex3f( 600, 410, 10 );
+        glColor3f(0, 0, 1.0);     glVertex3f( 600, 480, 10 );
+        glColor3f(1.0, 1.0, 1.0); glVertex3f( 410, 470, 10 );
+    glEnd();
+
+    SDL_GL_SwapBuffers();
+    
+#if !EMSCRIPTEN
+    // Wait for 3 seconds to give us a chance to see the image
+    SDL_Delay(30000);
+#endif
+
+    // Now we can delete the OpenGL texture and close down SDL
+    glDeleteTextures( 1, &texture );
+    
+    SDL_Quit();
+    
+    return 0;
+}