Add alpha blending of transparent textures

src/engine.cpp

@@ -64,7 +64,7 @@ int EngineInit(char *objFilename, char *mtlFilename)
 
 
     // Mesh configuration
-    mesh.position.z = 175;
+    mesh.position.z = 50;
     mesh.position.y = -175;
     mesh.scale = 1.0f;
 
@@ -152,29 +152,29 @@ static void CheckInputs(uint32_t input)
 
     if (CHECK_BIT(input, ROTATE_X_POS))
     {
-        mesh.position.x += 10;
+        mesh.rotation.x += 0.10f;
     }
     else if (CHECK_BIT(input, ROTATE_X_NEG))
     {
-        mesh.position.x -= 10;
+        mesh.rotation.x -= 0.10f;
     }
 
     if (CHECK_BIT(input, ROTATE_Y_POS))
     {
-        mesh.position.y += 10;
+        mesh.rotation.y += 0.10f;
     }
     else if (CHECK_BIT(input, ROTATE_Y_NEG))
     {
-        mesh.position.y -= 10;
+        mesh.rotation.y -= 0.10f;
     }
 
     if (CHECK_BIT(input, ROTATE_Z_POS))
     {
-        mesh.position.z += 10;
+        mesh.rotation.z += 0.10f;
     }
     else if (CHECK_BIT(input, ROTATE_Z_NEG))
     {
-        mesh.position.z -= 10;
+        mesh.rotation.z -= 0.10f;
     }
 
     if (CHECK_BIT(input, SCALE_UP))

src/loader.cpp

@@ -8,7 +8,7 @@
 
 
 // STATIC PROTOTYPES
-static int LoadTexture(char *filename, Texture &texture);
+static int LoadTexture(char *filename, Texture &texture, float opacity);
 
 
 #pragma pack(push, 1)
@@ -194,7 +194,9 @@ int ParseMTL(char *filename, EngineMemory &memory)
             {
                 char *textureFilename = data;
                 textureFilename[strcspn(textureFilename, "\r\n")] = 0;
-                LoadTexture(textureFilename, textures.data[materialIndex]);
+                LoadTexture(
+                        textureFilename, textures.data[materialIndex],
+                        materials.data[materialIndex].opacity);
             }
         }
     }
@@ -204,7 +206,7 @@ int ParseMTL(char *filename, EngineMemory &memory)
     return 0;
 }
 
-static int LoadTexture(char *filename, Texture &texture)
+static int LoadTexture(char *filename, Texture &texture, float opacity)
 {
     FILE *fp = fopen(filename, "r");
     if (fp == NULL)
@@ -227,6 +229,7 @@ static int LoadTexture(char *filename, Texture &texture)
             fread(&texture.texels[y][x].b, 1, 1, fp);
             fread(&texture.texels[y][x].g, 1, 1, fp);
             fread(&texture.texels[y][x].r, 1, 1, fp);
+            texture.texels[y][x].a = (uint8_t)(255 * opacity);
         }
 
         // Discard padding byte

src/render.cpp

@@ -114,24 +114,32 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                     float duDiff = 1 - du;
                     float dvDiff = 1 - dv;
 
-                    ColorU32 color;
-                    color.b = (uint8_t)
+                    ColorU32 color =
+                    {
+                        (uint8_t)
                             (duDiff * dvDiff * texture.texels[v][u].b
                              + du * dvDiff * texture.texels[v][u+1].b
                              + du * dv * texture.texels[v+1][u+1].b
-                         + duDiff * dv * texture.texels[v+1][u].b);
+                             + duDiff * dv * texture.texels[v+1][u].b),
 
-                    color.g = (uint8_t)
+                        (uint8_t)
                             (duDiff * dvDiff * texture.texels[v][u].g
                              + du * dvDiff * texture.texels[v][u+1].g
                              + du * dv * texture.texels[v+1][u+1].g
-                         + duDiff * dv * texture.texels[v+1][u].g);
+                             + duDiff * dv * texture.texels[v+1][u].g),
 
-                    color.r = (uint8_t)
+                        (uint8_t)
                             (duDiff * dvDiff * texture.texels[v][u].r
                              + du * dvDiff * texture.texels[v][u+1].r
                              + du * dv * texture.texels[v+1][u+1].r
-                         + duDiff * dv * texture.texels[v+1][u].r);
+                             + duDiff * dv * texture.texels[v+1][u].r),
+
+                        (uint8_t)
+                            (duDiff * dvDiff * texture.texels[v][u].a
+                             + du * dvDiff * texture.texels[v][u+1].a
+                             + du * dv * texture.texels[v+1][u+1].a
+                             + duDiff * dv * texture.texels[v+1][u].a)
+                    };
 
 
                     // Perform Gouraud shading on the texture
@@ -145,7 +153,7 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                         + (barycenter[2] * c2);
 
 
-                    // Ensure no color channel exceeds 1.0
+                    // Ensure no color channel exceeds max
                     ScaleColor(shading);
 
 
@@ -154,6 +162,7 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                     color.g *= shading.g;
                     color.r *= shading.r;
 
+
                     // Interpolate 1/z for the z-buffer
                     float zInv =
                         1.0f /
@@ -165,7 +174,21 @@ void Render(EngineBuffer &buffer, EngineMemory &memory)
                     // Draw the pixel if it's closer than what's in the z-buffer
                     if (zInv > memory.zbuffer[y][x])
                     {
-                        DrawPixel(buffer.buffer, buffer.width, color.u32, x, y);
+                        ColorU32 *pixel = (ColorU32*)&buffer.buffer[y*buffer.width+x];
+
+                        float alpha = color.a / 255.0f;
+                        float alphaDiff = 1.0f - alpha;
+
+                        // Blend new color with the existing color
+                        ColorU32 blended =
+                        {
+                            (uint8_t)((alpha * color.b) + (alphaDiff * pixel->b)),
+                            (uint8_t)((alpha * color.g) + (alphaDiff * pixel->g)),
+                            (uint8_t)((alpha * color.r) + (alphaDiff * pixel->r)),
+                            (uint8_t)((alpha * color.a) + (alphaDiff * pixel->a))
+                        };
+
+                        DrawPixel(buffer.buffer, buffer.width, blended.u32, x, y);
 
                         memory.zbuffer[y][x] = zInv;
                     }