Difference between "Merge" & "Group"

[Elez]

I have a question:

Which is the difference between merging and grouping two pieces?

Cheers.

[coppelia]

Hello,

• when you merge two shapes, you obtain a simple shape with a single color and attributes. Two merged shapes can not always be divided (unmerged) to restore the initial state.
• when you group two shapes, you obtain a grouped shape with different colors and attributes. You can always ungroup a grouped shape to restore the initial state.

Cheers

[Matthew Qi]

Hello,

• when you merge two shapes, you obtain a simple shape with a single color and attributes. Two merged shapes can not always be divided (unmerged) to restore the initial state.
• when you group two shapes, you obtain a grouped shape with different colors and attributes. You can always ungroup a grouped shape to restore the initial state.

Cheers

Hi,
Are there any other differences between "Merge" & "Group", such as simulation
Thanks

[coppelia]

Yes. When you merge two shapes, the result is a single shape. And this is also how the physics engine will see that merged shape: as a single shape.
Imagine two spheres that are pure shapes (i.e. primitive shapes). If you group them, the physics engine will still know it is dealing with two spheres and can optimize calculations for the spheres. If you merge the two spheres, the physics engine will not recognize the spheres anymore, and will simply handle them as a polygon soup, which is the worst for a physics engine: simulation stability will be bad, and calculation times high.

Cheers