some question about texturing using meshlab

Hello, I’m trying to generate texture coordinates using meshlab for an obj model. Now the way I’m following is as follows:

Filters > Texture > Parameterization: Trivial Per-Triangle or Parameterization: Flat Plane

Now, if I choose Parameterization: Trivial Per-Triangle, the texture mapping does not properly reflect the image. Next, if I choose Parameterization: Flat Plane, texture mapping is smooth and it reflects the image.

My question, I can make Parameterization: Trivial Per-Triangle working if I just follow the procedure, i.e. Filters > Texture > Parameterization: Trivial Per-Triangle.

But I cannot make Parameterization: Flat Plane (which I prefer) work using the following:Filters > Texture > Parameterization: Flat Plane;

It seems to make it (Parameterization: Flat Plane) work, before using Parameterization: Flat Plane, I’ve to use Parameterization: Trivial Per-Triangle. The process seems to have the following flow chart:

Filters > Texture > Parameterization: Trivial Per-Triangle > Parameterization: Flat Plane (instead of Filters > Texture > Parameterization: Trivial Per-Triangle

Does anyone using meshlab can clarify a bit? I also have question, why the texture mapping from Parameterization: Trivial Per-Triangle does not reflect the image properly, it looks very random.

Thanks in advance.