Add perspective SVG output (#1119)

* Added perspective SVG output

* Apply suggestion

* Change var name

* Simplify option handling

* Correct my own mistake

* One more fix

* "Pull" the latest rtd conf

---------

Co-authored-by: AU <[email protected]>

Author: RashKash103

cadquery/occ_impl/exporters/svg.py

@@ -144,6 +144,8 @@ def getSVG(shape, opts=None):
         strokeColor: Color of the line that visible edges are drawn with.
         hiddenColor: Color of the line that hidden edges are drawn with.
         showHidden: Whether or not to show hidden lines.
+        focus: If specified, creates a perspective SVG with the projector
+               at the distance specified.
     """
 
     # Available options and their defaults
@@ -158,6 +160,7 @@ def getSVG(shape, opts=None):
         "strokeColor": (0, 0, 0),  # RGB 0-255
         "hiddenColor": (160, 160, 160),  # RGB 0-255
         "showHidden": True,
+        "focus": None,
     }
 
     if opts:
@@ -176,11 +179,17 @@ def getSVG(shape, opts=None):
     strokeColor = tuple(d["strokeColor"])
     hiddenColor = tuple(d["hiddenColor"])
     showHidden = bool(d["showHidden"])
+    focus = float(d["focus"]) if d.get("focus") else None
 
     hlr = HLRBRep_Algo()
     hlr.Add(shape.wrapped)
 
-    projector = HLRAlgo_Projector(gp_Ax2(gp_Pnt(), gp_Dir(*projectionDir)))
+    coordinate_system = gp_Ax2(gp_Pnt(), gp_Dir(*projectionDir))
+
+    if focus is not None:
+        projector = HLRAlgo_Projector(coordinate_system, focus)
+    else:
+        projector = HLRAlgo_Projector(coordinate_system)
 
     hlr.Projector(projector)
     hlr.Update()

doc/_static/importexport/box_custom_options_perspective.svg

@@ -92,6 +92,7 @@ options are as follows.
 * *strokeColor* - Color of the line that visible edges are drawn with.
 * *hiddenColor* - Color of the line that hidden edges are drawn with.
 * *showHidden* - Whether or not to show hidden lines.
+* *focus* - If specified, creates a perspective SVG with the projector at the distance specified.
 
 The options are passed to the exporter in a dictionary, and can be left out to force the SVG to be created with default options. 
 Below are examples with and without options set.
@@ -144,6 +145,10 @@ Which results in the following image:
 
 ..  image:: _static/importexport/box_custom_options.svg
 
+Exporting with the additional option ``"focus": 25`` results in the following output SVG with perspective:
+
+.. image:: _static/importexport/box_custom_options_perspective.svg
+
 Exporting STL
 ##############
 

doc/importexport.rst

@@ -113,6 +113,7 @@ def testSVGOptions(self):
                 "strokeColor": (255, 0, 0),
                 "hiddenColor": (0, 0, 255),
                 "showHidden": True,
+                "focus": 4,
             },
         )