Additional frame buffer for post-process

Questions
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1

Hi folk, I’m just started to learn WebGL and shader for digging into more detail of rendering pipeline. So I’m very weak in a lot of basics here.

The question is, How can I attach the additional Frame Buffer to the ShaderMaterial?

For the background on why I want to achieve this.

I have a single mesh in the project which needs to create a glow effect on some of the faces.

For the performance reason, I can’t split those meshes into another cause there are already a lot of meshes in the scene.

I want to write glow parts into FBO in the fragment shader then use this to create the post-process.

If it is possible how could I do that?
And is this the way I should do it?

2

After searching around, I think what I’m looking for is the MRT feature.

Look like this example could help me

https://threejs.org/examples/?q=multiple#webgl2_multiple_rendertargets

Not sure if this is the proper way to achieve this…