orbit camera collision / limits (feature request?)

we made an extension script, which draws the limits as a mesh.
it is very hacky as of now, but helps iterate faster on the limits.

a nicer implementation as overlay / tool / handle would be nice, but not sure how this is possible in blender 2.8+.

import bpy, bmesh, mathutils, math

def draw():
    camera = bpy.context.active_object

    obj = bpy.context.scene.objects.get("debugCube")
    if not obj:
        mesh = bpy.data.meshes.new("debugCube")
        obj = bpy.data.objects.new(mesh.name, mesh)
        scene = bpy.context.scene
        scene.collection.objects.link(obj)
    else:
        mesh = obj.data

    verts = []
    edges = []
    faces = []

    # get camera limits
    tgt = camera.data.v3d.orbit_target
    pos = camera.location
    camDirection = pos-tgt
    near = camDirection.normalized()*camera.data.v3d.orbit_min_distance+tgt
    far  = camDirection.normalized()*camera.data.v3d.orbit_max_distance+tgt

    # add cross at target position
    def drawCross (position):
        verts.append(position-mathutils.Vector((0,1,0)))
        verts.append(position+mathutils.Vector((0,1,0)))
        verts.append(position-mathutils.Vector((1,0,0)))
        verts.append(position+mathutils.Vector((1,0,0)))
        verts.append(position-mathutils.Vector((0,0,0)))
        verts.append(position+mathutils.Vector((0,0,1)))
    drawCross(tgt)

    #add line from near to far, in camera direction
    verts.append(near)
    verts.append(far)

    #add circles
    count = 32

    #add circle for horizontal limits at near limit distance
    angle = camera.data.v3d.orbit_min_azimuth_angle
    endAngle = camera.data.v3d.orbit_max_azimuth_angle
    sweepAngle = endAngle-angle

    for i in range(count):
        angle += sweepAngle/count
        verts.append(mathutils.Vector((math.sin(angle),-math.cos(angle),0)) *camera.data.v3d.orbit_min_distance + tgt)

    #add circle for vertical limits at far limit distance    
    angle = camera.data.v3d.orbit_min_polar_angle
    endAngle = camera.data.v3d.orbit_max_polar_angle
    sweepAngle = endAngle-angle

    for i in range(count):
        angle += sweepAngle/count
        verts.append(mathutils.Vector((0,-math.sin(angle),math.cos(angle))) *camera.data.v3d.orbit_max_distance + tgt)

    for i in range(int(len(verts)/2)):
        edges.append([i*2,i*2+1])

    mesh.from_pydata(verts, edges, faces)

    #def emptyAtPosition (name, position, direction):
    #    obj = bpy.context.scene.objects.get(name)
    #    o = bpy.data.objects.new( "empty", None )

class DrawCameraLimits(bpy.types.Operator):
    """draw the camera limits as a 3d object"""
    bl_idname = "object.draw_limits"
    bl_label = "draw limits"
    bl_options = {'REGISTER', 'UNDO'}
      
    def execute(self, context):
        draw()
        return {'FINISHED'}
    
    

def menu_func(self, context):
    layout = self.layout
    print("test")
    layout.separator()
    layout.operator(DrawCameraLimits.bl_idname)

classes=[ DrawCameraLimits ]

def register():
    for c in classes:
        bpy.utils.register_class(c)
        
    bpy.types.V3D_PT_CameraSettings.append(menu_func)
    

def unregister():
    for c in classes:
        bpy.utils.unregister_class(c)
        
    bpy.types.V3D_PT_CameraSettings.remove(menu_func)
    

if __name__ == "__main__":
    register()

since we use these limits quite a lot, i had a deeper look at it, and updated it to use gizmos.
they are not perfect (some range visual instead of two circles would be nicer), but they help a lot speeding up the worflow to set up and change limits.

we packed it as an installable plugin, so others can use it easily: download the .py and install via the blender preferences.

feel free to integrate this one in a future verge3d release, if wanted.