Merge pull request #488 from ehsan/fog

Fix the fog if the distance is negative

4 files changed, 202 insertions, 7 deletions

diff --git a/src/library_gl.js b/src/library_gl.js
index 89603572..6a337d00 100644
--- a/src/library_gl.js
+++ b/src/library_gl.js
@@ -1111,6 +1111,10 @@ var LibraryGL = {
             source = 'uniform float u_fogScale;   \n' +
                      source.replace(/gl_Fog.scale/g, 'u_fogScale');
           }
+          if (source.indexOf('gl_Fog.density') >= 0) {
+            source = 'uniform float u_fogDensity;   \n' +
+                     source.replace(/gl_Fog.density/g, 'u_fogDensity');
+          }
           if (source.indexOf('gl_FogFragCoord') >= 0) {
             source = 'varying float v_fogFragCoord;   \n' +
                      source.replace(/gl_FogFragCoord/g, 'v_fogFragCoord');
@@ -1569,8 +1573,7 @@ var LibraryGL = {
               switch (GLEmulation.fogMode) {
                 case 0x0801: // GL_EXP2
                   // fog = exp(-(gl_Fog.density * gl_FogFragCoord)^2)
-                  var fogFormula = '  float density = float(' + GLEmulation.fogDensity + '); \n' +
-                                   '  float fog = exp(-density * density * ecDistance * ecDistance); \n';
+                  var fogFormula = '  float fog = exp(-u_fogDensity * u_fogDensity * ecDistance * ecDistance); \n';
                   break;
                 case 0x2601: // GL_LINEAR
                   // fog = (gl_Fog.end - gl_FogFragCoord) * gl_fog.scale
@@ -1578,8 +1581,7 @@ var LibraryGL = {
                   break;
                 default: // default to GL_EXP
                   // fog = exp(-gl_Fog.density * gl_FogFragCoord)
-                  var fogFormula = '  float density = float(' + GLEmulation.fogDensity + '); \n' +
-                                   '  float fog = exp(-density * ecDistance); \n';
+                  var fogFormula = '  float fog = exp(-u_fogDensity * ecDistance); \n';
                   break;
               }
             }
@@ -1597,7 +1599,7 @@ var LibraryGL = {
                                                        '  gl_Position = u_projection * ecPosition; \n' +
                                                        (hasTextures ? 'v_texCoord = a_texCoord0;    \n' : '') +
                                                        (colorSize ? 'v_color = a_color; \n' : 'v_color = u_color; \n') +
-                                                       (GLEmulation.fogEnabled ? 'v_fogFragCoord = ecPosition.z;\n' : '') +
+                                                       (GLEmulation.fogEnabled ? 'v_fogFragCoord = abs(ecPosition.z);\n' : '') +
                                                        '}                           \n');
             Module.ctx.compileShader(this.vertexShader);
 
@@ -1611,6 +1613,7 @@ var LibraryGL = {
                                                            'uniform vec4 u_fogColor; \n' +
                                                            'uniform float u_fogEnd; \n' +
                                                            'uniform float u_fogScale; \n' +
+                                                           'uniform float u_fogDensity; \n' +
                                                            'float ffog(in float ecDistance) { \n' +
                                                            fogFormula +
                                                            '  fog = clamp(fog, 0.0, 1.0); \n' +
@@ -1621,7 +1624,7 @@ var LibraryGL = {
                                                          '{                                                   \n' +
                                                          (hasTextures ? 'gl_FragColor = v_color * texture2D( u_texture, v_texCoord );\n' :
                                                                         'gl_FragColor = v_color;\n') +
-                                                         (GLEmulation.fogEnabled ? 'gl_FragColor = vec4(mix(vec3(u_fogColor), vec3(gl_FragColor), ffog(v_fogFragCoord)), gl_FragColor.a); \n' : '') +
+                                                         (GLEmulation.fogEnabled ? 'gl_FragColor = vec4(mix(u_fogColor.rgb, gl_FragColor.rgb, ffog(v_fogFragCoord)), gl_FragColor.a); \n' : '') +
                                                          '}                                                   \n');
             Module.ctx.compileShader(this.fragmentShader);
 
@@ -1661,7 +1664,9 @@ var LibraryGL = {
           this.fogColorLocation = Module.ctx.getUniformLocation(this.program, 'u_fogColor');
           this.fogEndLocation = Module.ctx.getUniformLocation(this.program, 'u_fogEnd');
           this.fogScaleLocation = Module.ctx.getUniformLocation(this.program, 'u_fogScale');
-          this.hasFog = !!(this.fogColorLocation || this.fogEndLocation || this.fogScaleLocation);
+          this.fogDensityLocation = Module.ctx.getUniformLocation(this.program, 'u_fogDensity');
+          this.hasFog = !!(this.fogColorLocation || this.fogEndLocation ||
+                           this.fogScaleLocation || this.fogDensityLocation);
         },
 
         prepare: function() {
@@ -1748,6 +1753,7 @@ var LibraryGL = {
             if (this.fogColorLocation) Module.ctx.uniform4fv(this.fogColorLocation, GLEmulation.fogColor);
             if (this.fogEndLocation) Module.ctx.uniform1f(this.fogEndLocation, GLEmulation.fogEnd);
             if (this.fogScaleLocation) Module.ctx.uniform1f(this.fogScaleLocation, 1/(GLEmulation.fogEnd - GLEmulation.fogStart));
+            if (this.fogDensityLocation) Module.ctx.uniform1f(this.fogDensityLocation, GLEmulation.fogDensity);
           }
         },
 
diff --git a/tests/runner.py b/tests/runner.py
index 654b0a97..b1c969f3 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -7683,6 +7683,13 @@ elif 'browser' in str(sys.argv):
       Popen(['python', EMCC, path_from_root('tests', 'sdl_fog_simple.c'), '-O2', '--minify', '0', '-o', 'something.html', '--pre-js', 'reftest.js', '--preload-file', 'screenshot.png']).communicate()
       self.run_browser('something.html', 'You should see an image with fog.', '/report_result?0')
 
+    def test_sdl_fog_negative(self):
+      # SDL, OpenGL, textures, fog, immediate mode. Closure for more coverage
+      shutil.copyfile(path_from_root('tests', 'screenshot.png'), os.path.join(self.get_dir(), 'screenshot.png'))
+      self.reftest(path_from_root('tests', 'screenshot-fog-negative.png'))
+      Popen(['python', EMCC, path_from_root('tests', 'sdl_fog_negative.c'), '-O2', '--minify', '0', '-o', 'something.html', '--pre-js', 'reftest.js', '--preload-file', 'screenshot.png']).communicate()
+      self.run_browser('something.html', 'You should see an image with fog.', '/report_result?0')
+
     def test_sdl_fog_density(self):
       # SDL, OpenGL, textures, fog, immediate mode. Closure for more coverage
       shutil.copyfile(path_from_root('tests', 'screenshot.png'), os.path.join(self.get_dir(), 'screenshot.png'))
diff --git a/tests/screenshot-fog-negative.png b/tests/screenshot-fog-negative.png
new file mode 100644
index 00000000..5b18a201
--- /dev/null
+++ b/tests/screenshot-fog-negative.png
diff --git a/tests/sdl_fog_negative.c b/tests/sdl_fog_negative.c
new file mode 100644
index 00000000..2d589a47
--- /dev/null
+++ b/tests/sdl_fog_negative.c
@@ -0,0 +1,182 @@
+/*******************************************************************
+ *                                                                 *
+ *                        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);
+
+    assert(glIsEnabled(GL_FOG));
+
+    glBegin( GL_QUADS );
+        glTexCoord2i( 0, 0 ); glVertex3f( 10, 10, -1 );
+        glTexCoord2i( 1, 0 ); glVertex3f( 300, 10, -1 );
+        glTexCoord2i( 1, 1 ); glVertex3f( 300, 128, -1 );
+        glTexCoord2i( 0, 1 ); glVertex3f( 10, 128, -1 );
+
+        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;
+}