Help with Components and Blocks

[honoluludesktop]

As I do not use Acad, can someone who uses it explain the relationship between Acad Blocks, and SketchUp Groups, Component Instances and Component Definitions? The following questions are based on my assumption that Acad Xrefs require an external file, without which are Acad Blocks.

1. Like SU Components, do Acad Blocks have duplicate instances within a Acad file?
2. If so, how are they distinguished, by their name?
3. Do these instances have transformations other then location?
4. I assume if the above is correct, a unique Block is simply one that doesn't have another instance.
5. If the above is wrong, what is the most correct description of the relationship between SketchUp Groups and Component, to Acad entities?

[Didier Bur]

Hi,

1. Yes, but that's not mandatory.
2. Instances of blocks have an ID's just like components, but on the user point of view they are not distinguishable. Their generic name appears in their properties.
3. Yes: rotation angle, scale along X,Y,Z (can be negative)
4. No, a unique block is a block automatically generated by Acad: hatches, boundaries, dimensions. Their name start with a * character. Note that a block can be defined in the drawing dictionnary but have no instances (just like if you create a component in a SU model and never use it.)
5. There are groups in Acad too, and pretty similar to SU groups. Blocks (I mean user blocks) can be seen as SU components: they have a definition in a dictionnary, can have single/multiple instances, can be updated just the way we update our components in SU, etc. But they have far more properties than SU components, that's beyond the scope of my knowledge in Autolisp (15 years ago or so...).
   Hope this helps,

[honoluludesktop]

Didier, Yes, thanks.

In Dxf, I think the entity Insert is used to apply transformation to a block (which is like a definition). Matching its name (I think) is what distinguishes it as a instance. Will test these assumptions tonight.

If a SU Component is the equivalent of the Acad entity Insert, what Acad entity is the equivalent of a SU Group, if any. Or can I treat it as a Insert without additional instances? Sorry if I my question seems repetitious.