Cosmographer 3-D Starmap Scale?

Ok, I have a weird problem. I created a Map 1000 X 800 - I assume that must be in light years?

When I measure 2 stars, top to bottom, I would expect about 800 light year separation, but I get about 1000. And when I measure horizontally, I would expect to get 1000, but I get 800?

Very weird...it's as if the dimensions are flipped, but the map appears fine on the screen and oriented as expected.

Any suggestions?

Comments

  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    edited September 2012
    Are you using the normal Tools -> distance,or are you using the special star distance ruler in the lefthand toolbar? The latter understands height value of the stars, so two stars that appear visually close can be really far away from each other (Like in the real sky. If you look up and see two stars close to each other, they may still be thousands of light years apart.)
    Posted By: hlong69I created a Map 1000 X 800 - I assume that must be in light years?
    Whatever you need it to be really. Stars and planets are not to scale (If they were, they would be to small to be visible in almost any sized map). Therefore, treat this value as whatever you need (AU, LY, PC, etc...)
  • edited September 2012
    I was using the special star ruler tool, and both planets had no Z value. I wanted to measure the distance across the map as a test, so I created one star on each edge then measure with the distance between star tool.
  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    The reason for this is that this map type uses an Isometric grid to get the correct perspective. This makes the calculated distances to appear visually illogical, although they are strictly correct.

    To see this visually, add an isometric grid to your drawing (Grid spacing 50 is ok for this drawing). Now, look at the "squares" in the grid. These are true squares, just projected for a 3D-view. You may notice that the distance from the top point to the bottom point is different from the distance from the left point to the right point. This is an artifact of the projection, in reality, these distances are the equal (in the system behind the scenes, the visible squares on the screen are definitely different). The tool however uses the true distance, which is why you get these seemingly weird (but correct) results.
  • edited September 2012
    That doesn't make sense to me. If the canvas is in X * Y Units, then I would expect a measurement of the X axis to yield X units, not Y units. Maybe Im missing something. Im not trying to be difficult....just want to figure this out so I can use it effectively :)
  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    The issue occurs because we have two different coordinate systems in play here. The canvas represent the coordinate system aligned to your actual screen, while the isometric grid represents the coordinate system used by the actual 3D view. Using two coordinate systems is a necessity to make a true isometric look on a flat screen/paper (the Perspectives add-on has the exact same issues). The star distance ruler measures according to the real coordinate system (the isometric one), and not the one defined by your screen/canvas. Again, this is necessary to provide a correct result of the distances.
    When setting the map (canvas) size, you define the area which the isometric system will be laid out inside, but due to the ways these two line up, these will never be identical. The values here will therefore serve as guidelines, but not exact values.

    When you measure the distance between two stars position at the X-axis of the map border, you are not really measuring along the map border, but rather across the isometric grid. Therefore, this distance is not equal to the distance of the map border occupying the same visual area on your screen, because the map border occupies a different coordinate system.

    These issues are why the special star distance ruler is needed in the first place, because this tool understands the true isometric coordinate system used in your map, as opposed to the regular distance tool which only understands "flat" views.
  • Ok, I did as you suggested and added the isometric grid, and was able to measure 50 unites between any angle of a single grid. Thats good at least I know how to use it.

    Thanks for your patience!

    Is there a way to set the center of a grid as the 0,0 point?
  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    Select Move Origin form the View menu. This allows you to move the origin (0,0) to wherever you want in the map. Use the snaps and/or modifiers to accomplish an exact placement
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