copied guide for render mode

docs/guide/render.md

@@ -6,17 +6,35 @@ permalink: /guide/render/
 
 # Render
 
-Welcome! This is Scotty3D's realistic, globally illuminated pathtracing rendering, capable of creating images of complex scenes using path tracing.
+Welcome! This is Scotty3D's realistic, globally illuminated pathtracing renderer, capable of creating images of complex scenes using path tracing.
 
 ## Moving Camera
 
 ## Create light
 
+To create a lighting for your scene, simply go to the menu on the left side, click "New Light", and you will be able to choose from a variaty of light objects and environmental lights. (you will implement the support for environmental light in Task 7. See the corresponding documentation for more guide.)
+
+![light](render_mode/light.png)
+
+## Render Window
+
+Click on "Open Render Window", and you will be able to set the parameters to render your model. Enjoy the excitement of seeing the images becoming clearer and clearer ;-)
+
+![light](render_mode/window.png)
+
 ## Enable Logged Ray for Debugging
 
+In Render mode, simply check the box for "Logged Rays", and you would be able to see the camera rays that you generated in task 1.
+
+![ray](render_mode/log_ray.png)
+
+
 ## Visualize BVH
 
-## Render Window
+In Render mode, simply check the box for "Logged Rays", and you would be able to see the camera rays that you generated in task 3 when you start rendering. You can click on the horizontal bar to see each level of your BVH.
+
+![ray](render_mode/bvh.png)
+