origin and xyz axes

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robint
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Joined: Tue Sep 25, 2018 8:20 pm

origin and xyz axes

Post by robint » Fri Sep 28, 2018 7:01 pm

Hi All

I feel like Im all over the place here. Can anyone show how I can revert to the sane world of an origin 0,0,0 and xyz axes as typical of 3D graphics apps

I havent found a reliable way to ground say opening a basic tetrahedron and flattening one face onto the xy plane with one edge on the x axis. Is there a way to show these axes for guidance?

I then want to export this as an equivalent dxf file with the same orientation as shown (4D will have to wait till 2019)

Talk about spaced out! :oops:

I know Im a toddler and you guys are all sprinters, pls bear with me, I come from a CAD world

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robertw
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Re: origin and xyz axes

Post by robertw » Sat Sep 29, 2018 5:08 am

I think I've answered most of this on your other posts, eg viewtopic.php?p=1723#p1723

There are options both for exporting and for viewing in Stella to orient a model in various ways.

robint
Posts: 13
Joined: Tue Sep 25, 2018 8:20 pm

Re: origin and xyz axes

Post by robint » Sat Sep 29, 2018 6:13 am

Thanx Rob

Im a night owl here its 6.13 am

I will follow through on your replies and try to get a method I can work with confidence.

I can live with x = r arrow, y = up arrow and z= out from screen. I assume this stays fixed (in the screen and yourself) and the model just swivels around in that space. This is the opposite of usual 3D CAD where the model is fixed to x,y,z coords and you swivel around the whole 3D space on screen but hit the button and you revert to the default orthogonal view and its origin 0,0,0

I think its the impetuous swirling around that is distracting, to say rotating about an axis in discrete steps of say 15deg, so I can orient myself. Ive seen "rotate about Axis option but not been able to use it cos my model has gone nuts already

As a toddler, I feel there is a need for a primer that takes you gently through basic operations (and start with Swirl switched off - its a kids toy), but thats my ACAD view but I can understand you are coming from a different direction involving abstract transforms of vertex tables, without ever having to draw a line. Ive seen your tutorial and it was way too fast for newbies IMHO. Maybe one of you loyal knowledgeable cohorts could put something together. I would be happy to assist as the tame newbie. To be effective it must be scripted and subtitled on screen. Keep sentences short slow and precise (no wibbling), give pause moments with examples to try and remember often your customers first language is not Strine :D

time for smokoh

Robin

robint
Posts: 13
Joined: Tue Sep 25, 2018 8:20 pm

Re: origin and xyz axes

Post by robint » Sat Sep 29, 2018 7:33 pm

Sorry Robert but unless the issues of orientation in the euclidian sense are properly addressed rather than skirted around, GS is never going to get past being a kids toy (IMHO)

I have tried your suggestions to my queries on controlling a model and they dont seem to run properly. There's no proper guidance wrt xyz coords and I cant fix axes of rotation (except by a crude step change window). Slightest mouse move and the model goes off the rails ( why no hot key for default orientation? - ctrl z just doesnt work, nor ctrl R). The model needs to have a lockable origin, and simple constrained axes for mouse rotation. There will also be a need to select a LCS for the model to display in isometric form (ie 45deg xlation from the s/w x,y z(out from screen)

Surely thats not too much to expect?

Also the colouring of faces issue is very fiddly. The rainbow button assigns different colours to different faces - helpful, but then annoyingly changes these colours as you rotate - useless - kids toy.

Is there a way to turn off dark shading of a face colour as you rotate - trying to build an orientation in my mind gets confused

Ive wasted an hour trying to do some quite elementary manipulations of a model in a controlled sense wrt GCS (global coord system) (in the CAD sense) :?:

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robertw
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Re: origin and xyz axes

Post by robertw » Sun Sep 30, 2018 4:56 am

I get the feeling you're not seeing what I'm seeing. You say the slightest mouse movement and the model goes off the rails? It should rotate at a sensible pace, roughly keeping the closest point of the model under the mouse. If it's rotating much faster than that for you, then something's different. What device are you on? Screen resolution, DPI?

Is it the ongoing spinning that you don't like after the mouse is released? It only spins if you're still moving the mouse when you release the button. But if you don't like it, disable it with "Options->Allow Mouse Inertia".

Ctrl+Z & Ctrl+R operate on changes to the model, not just changes to viewing angle etc. It's always annoying when software does that because it adds many times more items to the undo list, most of which are irrelevant to your changes. It also prevents you from viewing the undo/redo from different angles. It's not that these keys "don't work".

I guess I didn't add a hotkey for default orientation because I didn't think it was something people would use very often. Happy to add one though if we can find a spare key that makes sense.

I don't understand what you say about the origin. Is your model moving off-centre? The model only moves off-centre if you use Space+Left-drag.

There are some hotkeys you might like:
  • Esc - Stop auto-spinning
  • t - Tight-fit the model to the window. This also centres the model if it was off-centre.
  • f- Fit the model to the window, leaving room for rotation. This also centres the model if it was off-centre.
What do you mean that my suggestions "dont seem to run properly"? Are you saying my suggestions don't work, or just that they aren't what you wanted?

The point of rainbow colouring mode is to behave like a white model with red, green and blue lights shining at it from different directions, so yes as you rotate it faces will be lit differently by the different lights, getting different colours. It does what it's intended to do. If that's not what you're after, then don't use it, no need to call it a toy.

If you want every face to get a different colour, use "Color->Basic Colour Scheme->Color per Face (Unless Parallel)". There's lots of choices for colouring, plus you can manually change the colour of any face, or all faces, or all faces of the same type etc.

You CAN rotate a model around an axis. By default (I think) this is done with Space+Left+Right-drag, or Space+Middle-drag. But if you'll use it more often, you can get rid of the Space by enabling "Options->Left+Right-drag to Pivot Around Selected Item". Now if you have a middle mouse button, you can just do Middle-drag to rotate around a fixed axis. Select a face, edge, vertex, or symmetry axes, and it will rotate around that (or its centre in the case of faces & edges).

Actually it would be useful if I added "View->Orientation->Rotate Around Selected Face/Edge/Vertex/Symmetry". I might do that for the next version (which I'm afraid is still some time off).

Stella is mostly coordinate system agnostic. You shouldn't need to know about XYZ to deal with polyhedral geometry. What help would it be to see XYZ axes on the screen? I hear you saying that you miss these, coming from a CAD background, but I don't hear why you need them. Explain what you're trying to do and maybe we can help.

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