lighmaps

I cannot ask question directly in this thread so I am posting it here:

https://forum.unity3d.com/threads/directional-lightmaps.280716/

.."Realtime lightmaps take advantage of the same approach, and are subject to the same shading quality/cost tradeoffs. The only difference from the list above is that the Realtime Directional with Specular lightmap uses 3 textures (incoming intensity, direction, normal), taking 3 texture samples. It has a shading cost of one un-shadowed light, as it runs the BRDF only once. It works in combination with a realtime direct light, of course, which has it's own shading cost."..

Can anyone tell me how can I access these 3 textures in Unity shaderlab , especially the direction texture.

Thanks!