Polygon Rotation

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    • Polygon Rotation

      Hello

      I have a simple question about polygon rotation, that I couldn't find the answer in reference manual.
      I want to know what is the origin point of rotation in function GUI_RotatePolygon? I mean this function rotates the polygon around to which point?
      Can we change the origin point of rotation?

      Thank you

      The post was edited 1 time, last by Karim ().

    • Hello,

      the coordinates of polygon are considered related to the origin point when drawing the polygon.

      When rotating the polygon the origin point is the pivot point of the polygon that can be inside and outside the polygon depending on its coordinates.

      Аfter rotation is done you can draw rotated polygon related to the new origin point.

      C Source Code

      1. #include "DIALOG.h"
      2. // Source polygon
      3. // The coords of the polygon set that the origin and pivot point is inside the polygon
      4. GUI_POINT pSource1[] = { {-10, 10}, {-10, -90}, {0, -100}, {10, -90}, {10, 10} };
      5. // The coords of the polygon set that the origin and pivot point is outside the polygon
      6. GUI_POINT pSource2[] = { {-10, -20}, {-10, -90}, {0, -100}, {10, -90}, {10, -20} };
      7. // Rotated polygon
      8. GUI_POINT pDest1[5], pDest2[5];
      9. void MainTask(void) {
      10. GUI_Init();
      11. // Origin point is inside the polygon
      12. GUI_DispStringHCenterAt("Origin point is inside the polygon", 160, 10);
      13. // Draw the origin point (100, 120)
      14. GUI_DrawPoint(100, 120);
      15. // Draw the source polygon with the origin point
      16. GUI_DrawPolygon(pSource1, GUI_COUNTOF(pSource1), 100, 120);
      17. // Rotate the source polygon
      18. GUI_RotatePolygon(pDest1, pSource1, GUI_COUNTOF(pSource1), 45 * 0.01745329);
      19. GUI_SetColor(GUI_RED);
      20. // Draw the rotated polygon with the same origin point
      21. GUI_DrawPolygon(pDest1, GUI_COUNTOF(pDest1), 100, 120);
      22. GUI_SetColor(GUI_GREEN);
      23. // Draw the new origin point (300, 120)
      24. GUI_DrawPoint(300, 120);
      25. // Draw the rotated polygon with the new origin point
      26. GUI_DrawPolygon(pDest1, GUI_COUNTOF(pDest1), 300, 120);
      27. // Origin point is outside the polygon
      28. GUI_SetColor(GUI_WHITE);
      29. GUI_DispStringHCenterAt("Origin point is outside the polygon", 160, 170);
      30. // Draw the origin point (100, 280)
      31. GUI_DrawPoint(100, 280);
      32. // Draw the source polygon with the origin point
      33. GUI_DrawPolygon(pSource2, GUI_COUNTOF(pSource2), 100, 280);
      34. // Rotate the source polygon
      35. GUI_RotatePolygon(pDest2, pSource2, GUI_COUNTOF(pSource2), 45 * 0.01745329);
      36. GUI_SetColor(GUI_RED);
      37. // Draw the rotated polygon with the same origin point
      38. GUI_DrawPolygon(pDest2, GUI_COUNTOF(pDest2), 100, 280);
      39. GUI_SetColor(GUI_GREEN);
      40. // Draw the new origin point (300, 280)
      41. GUI_DrawPoint(300, 280);
      42. // Draw the rotated polygon with the new origin point
      43. GUI_DrawPolygon(pDest2, GUI_COUNTOF(pDest2), 300, 280);
      44. while (1);
      45. }
      Display All

      Alex.
    • Yes, we could say that, I suppose.

      I would say, the term of the origin point is applicable when drawing the polygon.

      Rotation of the polygon is doing in relative coordinates. When we are drawing rotated polygon we set the origin point again for drawing it in right place.

      Alex.