problem - Generate lightmap UV - unity

Suppose, when you want create your own lighting in unity editor. then you need to do some settings based on scenes. 

if you imported some 3D Assetes from any other 3D creation software (ex. I am using Blender) and then you need to generate lightmap UV to the respective model. when you do it and you got message like "Hold On". it will take more time or maybe freeze your pc.

In this case you need to understand that your imported model have high polygons and you must minimize the polygons without changing the model structure.

In blender, already have a decimate option but in some case that will not work. so then you need to install an external software called "MeshLab". you click on meshlab and download it.

Now, i am going to give you one youtube link that will show you how to decimate the high poly model to low poly.

In this video, you need to change one thing in quadric edge collapse decimation. you must check preserve boundry of the mesh that work for me.

then again you import that decimated model into unity editor  and it will work fine...

I hope this information will help you to solve your problem.