Bug Fix Closed Loop - #3522
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| :param outline_color: The color of the polygon's outline | ||
| :param fill_color: The color used to fill the polygon, or None if no fill | ||
| :param line_width: The line width of the polygon's outline | ||
| :param closed: whether the GLPolygon is closed or not |
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I think this naming or doc can be improved a bit to be more specific as to the fact that by "closed" we mean include the final segment from the last point to the initial.
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Not sure if this is good enough:
:param closed: If true, connect the first and the last point to form a
closed shape. Otherwise, the shape is left open.
| render_points = self.points + [self.points[0]] if self.is_closed else self.points | ||
| vertices = [(point[0], point[1], 0) for point in render_points] | ||
| self.setData(pos=vertices) | ||
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Should vertices contain the duplicate self.points[0] when the polygon is closed? I thought vertices means independent vertices so it should copy from points instead of render_points.
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Should vertices contain the duplicate self.points[0] when the polygon is closed?
I believe the answer is yes.
The vertices for the following must be [A, B, D, C, A]
A -- B
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C -- D
If the vertices are [A, B, D, C], it will render the following:
A -- B
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C -- D
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Actually, I have done a bit more digging, you did bring up a fairly interesting point.
The inheritance diagram works like the following:
GLPolygon -> GLShape ->GLLinePlotItem
The fundamental problem here is that we probably want a GL_LINE_LOOP instead of a GL_LINE_STRIP:
I am not sure if there is a easy fix without sending a patch to pyqtgraph.
CC: @williamckha
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Now that you are getting me thinking about this class, I feel like there should be a clearer definition for what is a "polygon" especially since we can form an "open looped" shape. The notion of an "open" polygon feels a bit strange and leaves some ambiguity about how this class may handle lists of points with <3 points in them (since geometrically, that cannot form a polygon.
I think we should either be more explicit with the fact that this class can support any number of points greater than 0, and guard against cases where a closed loop is used with fewer than 3 points (since this can have unintended rendering consequences for the caller).
Otherwise, the more software-y approach here would be to abstract the class into some GL Line class (unless this is what GLLinePlotItem is, but I haven't looked into that class yet). Hence, we can clearly define polygons as ALWAYS closed loops and have their rendering inherit from GL Line.
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Yea I agree that this should be a different class that better describes a series of line segments, cause my first thought of rendering for example the path of a robot would definitely not be a polygon
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| self.set_points(points) | ||
| self.is_closed = closed |
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I am a bit confused by why the initialization of is_closed. Have we used the constructor parameter "closed" at all, and is there a reason why we set is_closed after calling set_points?
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Thanks, I think you just discovered a bug that is not caught!
I will move self.is_closed one line above self.set_points(points).
My guess is that set_points is called after the construction of this class so this bug is never discovered.
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What I see on my end. You can see closed and open shapes. |
| if not self.points: | ||
| return |
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What are your thoughts on logging something here as an error/warning? I think this error could easily be buried otherwise if we just silently return early.
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I'm not sure I understand what exactly an 'open' shape is. I don't see how it exists in the screenshot sent. Do we even need to support something like this? |
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EDIT: @GrayHoang I'm pretty sure its solving this issue where paths for the robots are rendered as a closed shape. 
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I left another comment above, but I think this should be a separate class instead of implementing "open shapes" for the GLPolygon class |
nycrat
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The visuals look good.
But about the code itself, my suggestion is that the GLPolygon class should not be used for "open shapes". I think instead, it would be better to refactor it into a GLLineStrip class, and then create GLPolygon as a child class of GLLineStrip which just changes the constructor slightly to both:
- guard against a polygon with less than 3 points
- add the extra point that connects the lines
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see #3598 |
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I'll work on a description later.
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It is the reviewers responsibility to also make sure every item here has been covered
.hfile) should have a javadoc style comment at the start of them. For examples, see the functions defined inthunderbots/software/geom. Similarly, all classes should have an associated Javadoc comment explaining the purpose of the class.TODO(or similar) statements should either be completed or associated with a github issue