Add new resource for PG

dist/preview release/what's new.md

@@ -5,6 +5,7 @@
 ### Major updates
  - WebGL2 context support. WebGL2 is now used instead of WebGL 1 when available. [More info here](http://doc.babylonjs.com/overviews/webgl2) ([deltakosh](https://github.com/deltakosh))
  - Complete WebVR 1.1 support including controllers for HTC Vive and Occulus. [More info here](http://doc.babylonjs.com/overviews/webvr_camera) ([raanan](https://github.com/raananw))
+ - Complete rewrite of PBRMaterial. Introduced two new helper materials: `pbrMetallicRoughnessMaterial` and `pbrSpecularGlossinessMaterial`. [Demo](http://www.babylonjs.com/demos/pbrglossy/) - [More info here](http://doc.babylonjs.com/overviews/physically_based_rendering) ([Sebastien Vandenberghe](https://github.com/sebavan))
  - Support for Morph Targets. [More info here](http://doc.babylonjs.com/tutorials/how_to_use_morphtargets) ([deltakosh](https://github.com/deltakosh))
  - New Babylon.GUI to create user interface (compatible with WebVR). [More info here](http://doc.babylonjs.com/overviews/Gui) ([deltakosh](https://github.com/deltakosh))
  - Added support for Exponential Shadow maps to replace Variance Shadow maps. [more info here](http://www.babylonjs-playground.com/debug.html#1CXNXC#3) [Demo#1](http://www.babylonjs.com/Demos/AdvancedShadows/) [Demo#2](http://www.babylonjs-playground.com/#1CXNXC#4) ([deltakosh](https://github.com/deltakosh))
@@ -131,3 +132,9 @@
   - `LongPressDelay` and `DragMovementThreshold` are now respectively Scene.LongPressDelay and Scene.DragMovementThreshold
 - HDRRenderingPipeline:
   - `HDRRenderingPipeline` has been removed because it is deprecated. It is now replaced by `StandardRenderingPipeline` which is more advanced. See [documentation](http://doc.babylonjs.com/tutorials/using_standard_rendering_pipeline)
+- PBRMaterial:
+  - Fixed several bugs which could lead to visual changes. [More info here](http://www.html5gamedevs.com/topic/30754-pbr-breaking-changes/)
+  - Removed all overloadedXXX properties
+  - Removed all fresnelXXX properties
+  - Removed .babylon.hdr textures: We now use DDS files.
+

src/Materials/PBR/babylon.pbrMetallicRoughnessMaterial.ts

@@ -2,7 +2,7 @@
     /**
      * The PBR material of BJS following the metal roughness convention.
      * 
-     * This fits to the define PBR convention in the GLTF definition: 
+     * This fits to the PBR convention in the GLTF definition: 
      * https://github.com/KhronosGroup/glTF/tree/2.0/specification/2.0
      */
     export class PBRMetallicRoughnessMaterial extends Internals.PBRBaseSimpleMaterial {

src/Materials/PBR/babylon.pbrSpecularGlossinessMaterial.ts

@@ -2,7 +2,7 @@
     /**
      * The PBR material of BJS following the specular glossiness convention.
      * 
-     * This fits to the define PBR convention in the GLTF definition: 
+     * This fits to the PBR convention in the GLTF definition: 
      * https://github.com/KhronosGroup/glTF/tree/2.0/extensions/Khronos/KHR_materials_pbrSpecularGlossiness
      */
     export class PBRSpecularGlossinessMaterial extends Internals.PBRBaseSimpleMaterial {