Implementation

• Standard Surface Shader using alpha:blend to control the transparency.
• Setting RenderType and Queue to Transparent, and disabling ZWrite.
• Writing a second Pass for the Surface Shader with alphatest and addshadow, to create shadows that match the transparency.
• Writing refractions and reflections from scratch in an Unlit shader.
• Using GrabPass to get a texture with the current pixels in the Frame Buffer.
• Using ComputeGrabScreenPos, tex2Dproj and UNITY_PROJ_COORD to get the pixel from the GrabPass texture.
• Distorting the GrabPass pixel with the Normal Map, to generate refraction.
• Using the SkyBox/CubeMap texture to create environmental reflections.
• Using WorldSpaceViewDir to obtain the direction of the camera to the pixel.
• Using the built in Cg function reflect(), to get the reflection vector along the normal vector in world space (From UnityObjectToWorldNormal).
• Finally getting the reflection color by sampling the cube texture with texCUBE and the reflection vector.