added correct usage of mra map textures

RMA maps store Roughness as Red channel, Metalness as Green, and Ambient occlusion as Blue.
Added functionality to use these maps for accurate pbr materials.

examples/shaders/shaders_basic_pbr.c

@@ -22,7 +22,7 @@
 #if defined(PLATFORM_DESKTOP)
     #define GLSL_VERSION            330
 #else   // PLATFORM_ANDROID, PLATFORM_WEB
-    #define GLSL_VERSION            100
+    #define GLSL_VERSION            120
 #endif
 
 #include <stdlib.h>             // Required for: NULL
@@ -84,7 +84,7 @@ int main()
     const int screenHeight = 450;
 
     SetConfigFlags(FLAG_MSAA_4X_HINT);
-    InitWindow(screenWidth, screenHeight, "raylib [shaders] example - basic pbr");
+    InitWindow(screenWidth, screenHeight, "basic pbr");
 
     // Define the camera to look into our 3d world
     Camera camera = { 0 };
@@ -143,10 +143,17 @@ int main()
     car.materials[0].maps[MATERIAL_MAP_ROUGHNESS].value = 0.0f;
     car.materials[0].maps[MATERIAL_MAP_OCCLUSION].value = 1.0f;
     car.materials[0].maps[MATERIAL_MAP_EMISSION].color = (Color){ 255, 162, 0, 255 };
-
     // Setup materials[0].maps default textures
     car.materials[0].maps[MATERIAL_MAP_ALBEDO].texture = LoadTexture("resources/old_car_d.png");
-    car.materials[0].maps[MATERIAL_MAP_METALNESS].texture = LoadTexture("resources/old_car_mra.png");
+    
+    //Load RMA texture and convert it to an image to extract channels
+    Texture2D carTexture=LoadTexture("resources/old_car_mra.png");
+    Image carImage =LoadImageFromTexture(carTexture);
+    //RMA textures -> R corresponds to Roughness, G to Metalness, and B to Occlusion
+    //Using different channels of RMA map for different parameters
+    car.materials[0].maps[MATERIAL_MAP_METALNESS].texture = LoadTextureFromImage(ImageFromChannel(carImage,1));
+    car.materials[0].maps[MATERIAL_MAP_ROUGHNESS].texture = LoadTextureFromImage(ImageFromChannel(carImage,0));
+    car.materials[0].maps[MATERIAL_MAP_OCCLUSION].texture = LoadTextureFromImage(ImageFromChannel(carImage,2));
     car.materials[0].maps[MATERIAL_MAP_NORMAL].texture = LoadTexture("resources/old_car_n.png");
     car.materials[0].maps[MATERIAL_MAP_EMISSION].texture = LoadTexture("resources/old_car_e.png");
     
@@ -165,9 +172,14 @@ int main()
     floor.materials[0].maps[MATERIAL_MAP_ROUGHNESS].value = 0.0f;
     floor.materials[0].maps[MATERIAL_MAP_OCCLUSION].value = 1.0f;
     floor.materials[0].maps[MATERIAL_MAP_EMISSION].color = BLACK;
-
     floor.materials[0].maps[MATERIAL_MAP_ALBEDO].texture = LoadTexture("resources/road_a.png");
-    floor.materials[0].maps[MATERIAL_MAP_METALNESS].texture = LoadTexture("resources/road_mra.png");
+
+    Texture2D floorTexture=LoadTexture("resources/road_mra.png");
+    Image floorImage=LoadImageFromTexture(floorTexture);
+    //Using different channels of RMA map for different parameters
+    floor.materials[0].maps[MATERIAL_MAP_METALNESS].texture = LoadTextureFromImage(ImageFromChannel(floorImage,1));
+    floor.materials[0].maps[MATERIAL_MAP_ROUGHNESS].texture = LoadTextureFromImage(ImageFromChannel(floorImage,0));
+    floor.materials[0].maps[MATERIAL_MAP_OCCLUSION].texture = LoadTextureFromImage(ImageFromChannel(floorImage,2));
     floor.materials[0].maps[MATERIAL_MAP_NORMAL].texture = LoadTexture("resources/road_n.png");
 
     // Models texture tiling parameter can be stored in the Material struct if required (CURRENTLY NOT USED)
@@ -199,7 +211,7 @@ int main()
         // Update
         //----------------------------------------------------------------------------------
         UpdateCamera(&camera, CAMERA_ORBITAL);
-
+        //if (IsKeyPressedRepeat(KEY_RIGHT)){UpdateCamera(&camera,CAMERA_ORBITAL);};
         // Update the shader with the camera view vector (points towards { 0.0f, 0.0f, 0.0f })
         float cameraPos[3] = {camera.position.x, camera.position.y, camera.position.z};
         SetShaderValue(shader, shader.locs[SHADER_LOC_VECTOR_VIEW], cameraPos, SHADER_UNIFORM_VEC3);
@@ -251,7 +263,7 @@ int main()
             
             DrawText("Toggle lights: [1][2][3][4]", 10, 40, 20, LIGHTGRAY);
 
-            DrawText("(c) Old Rusty Car model by Renafox (https://skfb.ly/LxRy)", screenWidth - 320, screenHeight - 20, 10, LIGHTGRAY);
+            //DrawText("(c) Old Rusty Car model by Renafox (https://skfb.ly/LxRy)", screenWidth - 320, screenHeight - 20, 10, LIGHTGRAY);
             
             DrawFPS(10, 10);
 
@@ -261,8 +273,14 @@ int main()
 
     // De-Initialization
     //--------------------------------------------------------------------------------------
+    UnloadImage(floorImage);
+    UnloadTexture(floorTexture);
+    UnloadImage(carImage);
+    UnloadTexture(carTexture);
     // Unbind (disconnect) shader from car.material[0] 
     // to avoid UnloadMaterial() trying to unload it automatically
+    
+    
     car.materials[0].shader = (Shader){ 0 };
     UnloadMaterial(car.materials[0]);
     car.materials[0].maps = NULL;