SketchUp entities and their properties
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Revised: 2/19/09
As a beginner, the following took me almost a entire day to understand. It helps me understand my model, and especially scenes of the model. Please correct, where wrong.
My understanding is that in concept, SU has no lines, only the edges of surfaces, except when surfaces are removed and their edges are not, or a unclosed edge is drawn. That the "line" tool's function is to create edged surfaces.
A entity is a SU primitive.
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A entity can only be on one layer.
A edge is a 2D line entity in 3D space.
A surface is a edged 2D plane (entity) in 3D space.-
Adjoining surfaces share common edges.
A layer is a non spatial location of lines and/or surfaces.
- One layer is always active (visible).
- The active or component layers remains visible.
- Other layers can be visible or not.
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New and merged entities are placed on the active layer.
A group is a unique collection of entities within a model.
- Groups can not share surfaces.
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A group is a model entity (?).
A component instance is comprised of component definition.
- Component's definition include SU entities, and their properties.
-- Properties are shared (like color) or unshared (like scale). - A component instance is a model entity (?).
- Component's shared properties are common to all instances.
- Instances by selection can not share common entities.
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Instances by definition can be placed anywhere. - Exploded component's wholly overlapped entities are merged.
A scene (among other things) is a collection visible layers.
Anyone care to expand to include materials, etc.?
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@honoluludesktop said:
A scene (among other things) is a collection visible layers...
And
the applied style,
camera location,
...
and all the things that are listed here:
Good thread! Some basic concepts that can otherwise be understood only after long use of SU.
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@honoluludesktop said:
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A surface always includes 4 edges.
nitpicking...
I would say a surface always includes at least three edges.
(Three points determine a plane.) -
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In fact in SU, a surface can have n edges. What I was trying to say is a surface must come with edges.
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@honoluludesktop said:
A entity can only be on one layer.
Yeah, but groups and components are entities. And a group entity can be on Layer 0 and all its contents be on Layer 100. Or its contents can be split up on all sorts of layers.
@honoluludesktop said:
Groups can not share surfaces.
That sounds mis-leading to me in that they can have faces in the exact same 3d location. Maybe they can't share entities sounds better in my mind.
@honoluludesktop said:
A component instance are entities that comprise a component definition.
I'd reverse the order of these. First comes the definition, then comes the instances (sort of). The definition is aptly named because it is the base "definition" for the instances. The definition is what is shown in the components browser. Once you select the definition to insert into the model, you then have an instance inserted in the model. So all components are instances (except the definition shown in the comp. browser).
@honoluludesktop said:
- Component properties are common to all instances.
Instances actually can have different properties than the definition. The X,Y,Z location, any changes in scale, and materails applied to the outside of the instance, are all properties that are saved uniquely to each instance.
@honoluludesktop said:
- Component instance comprises of its definition.
Yes, as a a starting point. Like I pointed out above, the instance when inserted into the model is an exact copy of the definition. But scaling it, applying a material to it, or moving it will change properties to that instance. Oh, and all these properties can be changed without making the component unique or different than its definition.
@honoluludesktop said:
A scene (among other things) is a collection visible layers.
A scene is a collection of visible layers (among other things)
And I would love to detail all those other things, because I think that scenes are much more useful than many people realize. Its all in the "among other things" that there is some great functionality.Anyhow, those my thoughts. Maybe I'll chime back in on this later. I like this thread,
Chris
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@chris fullmer said:
@honoluludesktop said:
A entity can only be on one layer.
Yeah, but groups and components are entities. And a group entity can be on Layer 0 and all its contents be on Layer 100. Or its contents can be split up on all sorts of layers.
I wondered about this; by (my) definition, entities are primitives. That is they can not be broken down into more basic elements. What do you think?
@chris fullmer said:
@honoluludesktop said:
Groups can not share surfaces.
That sounds mis-leading to me in that they can have faces in the exact same 3d location. Maybe they can't share entities sounds better in my mind.
Tried it. Couldn't make two groups share the same surface. However, two components can share the same space.
@chris fullmer said:
@honoluludesktop said:
A component instance are entities that comprise a component definition.
I'd reverse the order of these. First comes the definition, then comes the instances (sort of). The definition is aptly named because it is the base "definition" for the instances. The definition is what is shown in the components browser. Once you select the definition to insert into the model, you then have an instance inserted in the model. So all components are instances (except the definition shown in the comp. browser).
Let me think about this. An instant is part of the model, a definition is data noted in the component browser and outline.
@chris fullmer said:
@honoluludesktop said:
- Component properties are common to all instances.
Instances actually can have different properties than the definition. The X,Y,Z location, any changes in scale, and materials applied to the outside of the instance, are all properties that are saved uniquely to each instance.
I was thinking of the things that an instance of a component share with other instances of that component.
@chris fullmer said:
@honoluludesktop said:
- Component instance comprises of its definition.
Yes, as a a starting point. Like I pointed out above, the instance when inserted into the model is an exact copy of the definition. But scaling it, applying a material to it, or moving it will change properties to that instance. Oh, and all these properties can be changed without making the component unique or different than its definition.
S***, when I scale a component, it scales by itself, but each instance's common surface, can share common property (like color). So we have properties that are shared (like color), and those that are unshared (like scale). Is scale a property, or should it defined in another way?
@chris fullmer said:
@honoluludesktop said:
A scene (among other things) is a collection visible layers.
A scene is a collection of visible layers (among other things)
And I would love to detail all those other things, because I think that scenes are much more useful than many people realize. Its all in the "among other things" that there is some great functionality.Perhaps too complex for elegant definition?
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