Bit later than I thought but had a busy weekend!
This might be in a bit of a random order just writing things as I think of them.
Sketchup without the add-on tools is best at boxy non organic forms, why something like 80% of architects use it now apparently. It's still not as flexible for organic shapes like Blender, Rhino3d etc. but for engineering/spacecraft stuff I think it works very well.
A few things I learnt the hard way and can drive you mad early on. When you start a model go to Window > Model Info > Units and set the precision and whether you want to enable length snapping. Precision is logical if you are building something small you probably want 0.000mm (or similar in inches) and length snapping can be useful until you get to really small moves and it won't let you if it's on or it jumps.
Also in the model info page under components you can adjust the visibility of similar (cloned) components and the rest of the model when editing.
Also under Window > Styles then the Edit tab you can set the front and back (inside) colour of the faces, it defaults to white and pale grey, which can be hard to distinguish so change one to something more obvious, I usually go for red as the back colour so it stands out.
Under Window > Preferences > General you can choose if and how often it creates an auto-save file, handy but can cause it to crash when you are in the exact moment of moving a large piece of geometry, usually you are ok just restarting and it prompts the auto-save is newer, but it can generate the same mid move which can be annoying, so you have to go back to the previous manual save. So as a simple rule save often under revision files names 01, 02, 03 etc so you can always go back if you or it screws up!
While we are talking components a quick and easy explanation. If you just want a part(s) not to interact with other geometry and move as one select them > right click and choose make group. This way they can cross other parts without merging or making new geometry you don't want. By default Sketchup wants things to be joined together.
Making a component takes it a stage further as you can make a "master" named component then clone it. The copies will then all change when you change the master, you can stop this behaviour by right clicking the copy and choosing make unique. Found this really handy when building tailfins of the Firefox as you can keep the master level to edit the profile while the "clones" can be rotated to the correct angle.
Note about groups and components, you can apply a colour to the selected group or component as sort of a master override independent of individual faces, but it has driven me mad in the past trying to get rid of it so try and go into a group or component (double-click on it) then select and color inside. If you want to colour sections use layers and the color by layer override in the Layers window.
There is also an option to colour edges by X, Y, Z direction which I can't find by at the moment, but I know it's there!
Selecting parts is something I learnt quite late on and was a godsend when I did. If you create a selection box by clicking and moving the mouse right and down (so starting the box with the top left corner) it selects only parts that fall completely in that box.
If you start a selection box by clicking and moving the mouse left and up (so starting the box with the bottom right corner) it selects everything that touches that box.
These can be combined with holding down shift while selecting will do an addition or subtraction selection based on what you have already selected, selecting arrow shows a + and - symbol. Holding down Control forces adding selections and Shift + Control forces de-selection, again the pointer arrow shows a - or + symbol respectively.
When moving, and this one drove me mad because I misunderstood it, you only have to tap the left, right or up arrow keys to lock the movement in the X,Y or Z direction, don't hold it down like I did at first and couldn't understand why it behaved like it was possessed!
Circles and arc are created with 24 and 12 segments by default, so if you are creating one where the resolution might be visible when printed increase it right clicking to get Entity info or just have the windows visible all the time by selecting it from the Window menu.
A point about this is if you extrude a circle it auto-softens the segment lines so it looks smooth, if you want to see more what your printed model will look like you need to unsoften the edges, most direct way is from the Soften Edges window, select edges, untick Smooth normals and then lower the angle between normals slider. To you wan the fully smoothed look so all hidden geometry edges disappear even on flat segmented surfaces you have to tick Soften Coplanar.
Before I forget stay with version 2015 as these is a 2016 version but there's no guarantee the plug-ins will work properly with it unless the author has updated them, it does appear most of them are up to date.
Plug ins - First sign up with
http://sketchucation.com and get the sketchucation extension that lets you search and auto install plug ins within Sketchup, makes it hassle free, although occasionally the search doesn't seem to work the same as on the website, mostly just a name matching glitch I think.
Very useful plug-ins are:
There are a whole bunch of plugins done by someone called Fredo which are brilliant
Fredo6: LibFredo6 - Shared library needed by many of the Fredo plugins. It is NOT a standalone plugin - get this first, all the Fredo tools look like they are 2016 compatible.
Fredo6: Curvizard - A suite of interactive tools operating on sequences of edges (Contours) and Sketchup curves. Lets you weld edges together, handy if you accidentally cut a section as this can make it such the push/pull and offset tools won't work the way you expect.
Fredo6: Curviloft - Dedicated to Loft and Skinning, that is, generation of surfaces from contours.
I build about 60% of models with this, the loft function is perfect for wingsections or transition from say a circle to a square etc. The skinning function will "skin" geometry. Both of these have a couple of glitches
1. If you have overlapping geometry such as a part that on it's own and part of a group existing in the same space it can get unhappy. I kept getting a "pinhole errors found" which wouldn't let the tool complete. Sometimes just saving, quitting and reloading fixed it, other time I have copied the pieces (use move plus a tap on the Control key) a fixed amount in say X direction then move the loft section back and delete the copied pieces.
2. It can see what it thinks are breaks in edges which it flags with a small purple square, and won't complete, so again doing the copy and move to create is often the easy solution or by using Curvizard > Make curves (weld) tools to make seperate geometry lines a whole.
Also discovered recently you can control how it makes the loft by grouping portions together in equal number of segments.
Good video here from about half way through
https://www.youtube.com/watch?v=yxqn145Q274
Fredo6: FredoScale -Interactively apply a number of geometric transformations, such as Scaling, Tapering, Stretching, Plane Shear, Twisting, Bending and Rotation. Adds the missing functionality from the standard scale tool, kind of stupid Sketchup didn't include this really.
Fredo6: Joint Push Pull Interactive - New version of JointPushPull, more interactive and with introduction of 3 new tools: Extrude, Round and Follow. Expands the functionallity of the push/pull tool so you can select multiple faces control the direction etc.
Fredo6: RoundCorner - Performs the rounding of the edges and corners of 3D shapes along a 2D profile, in 3 modes: Round corners, Sharp corners and Bevel.
Fredo6: Tools On Surface - A suite of Tools for drawing on curved surfaces, with lines, various shapes, offset and Freehand / Polyline. It provides an inference mechanism, a Contour Editor and a dedicated Eraser.
TIG: Mirror - Mirror selected objects by picking 1/2/3 points to define a point/line/plane: then choose to Keep/Delete the original objects.
s4u-Make face - closes holes essentially, although can create internal faces if the geometry lines up. Useful when slicing complex models for STL export as it will fix possible geometry holes. Also can fix incomplete OBJ files when they are imported, sometimes they have the geometry lines but not completed triangles so the geometry disappears when you try and export it.
Whaat: Artisan [Trial] - Organic Toolset for powerful subdivision, sculpting, and soft selection tools. This Next-Gen extension for SketchUp is a free 15 day trial. This one you have to pay for but can be very useful, there are videos on youtube showing what it can do.
These appear under the Extensions menu not as a toolbar
thomthom: TT Library - A library of reusable code, which is used to organize and manage many of TT's plugins, below
TIG: Import OBJ with Materials - Imports OBJ files with Materials, choice of Units, YZ axis flip etc...
TIG: Triangulate Faces - Triangulates face
, and all Texture UVs are kept.
Anton Synytsia: FixIt_101 - Attempts to turn groups into solids. The primary purpose was to automatically finish holes, but it looks like its quite successful in attempting to solidify the object too. Careful with this one, it does correct models well for STL output, but can get confused with nested groups and loft/skinning objects and just delete them!
thomthom: CleanUp - Optimize and clean up a model. Brilliant at removing unwanted geometry and duplicate faces, I set the options in Clean the I have it set to a shortcut key for easy access.
Draw menu tool
John McClenahan: SU Draw Parametric Shapes - This plugin enables Sketchup users to draw and place as component and edit, common 3D geometric shapes by specifying in a dialogue box their size and (where relevant) the number of segments to use when drawing shapes based on circles, polygons, or helix. Basically a shapes create like 3Dmaxs and Blender.
Will add to this as things come to mind
Jon