Primitive: 3D Face

[s-trinh]

A 3D face can be modeled by 3 to N points. The order of the points can matter when computing the visibility from face normal.

Interaction description:

• in edit mode, the user selects a particular point, he can see the corresponding coordinate in the transform > vertex field (as usual)
• the user clicks on a button to add the current selected point in the list

• a proposal is to use a drop down list to display the desired point in the list
• the user can also use the drop down list to select the point he wants to edit in the text boxes below
• if possible, the user selects multiple points and can then add all the selected points in the list

[vikasTmz]

Is this feature introduced here and in #6 an alternate to simplifying a model? Like instead of simplifying just choose the important contour points?

[s-trinh]

Yes, after some reflexion, we prefer the approach where the user selects directly the contour points he wants for 3D lines and 3D faces:

• it is easier to use for a novice user
• no need to prefilter the CAD model
• more flexible: the user can model some primitives, test the tracking, model other primitives or remove some elements, test, etc.

[vikasTmz]

From #8

in complex CAD models we have, the object is not decomposed of multiple primitives in the object tree view and we don't want to force the user to prefilter and/or group each primitive in a specific group

Simplifying or decomposing models isn't difficult once important vertices are selected. Below are some simple steps that can be done to generate faces from the selected vertices.

1. Select vertices

2. Y to seperate vertices/ edges and P to create a new mesh for those separated vertices/ edges

3. Now the user can select edges/vertices/faces and then X to delete them. Limited Dissolve can now be used to reduce number of vertices/ edges further and maintain the contour [this step is optional]

4. F to create a face from the new set of vertices

[vikasTmz]

The advantage of having these primitives exist in the scene is it would be easy to manage them. But if they are to be managed in a list as just data points, the list would be very large for even a simple model like cubesat and it would be hard for the user then to remove/ disable a random list of points/ lines from the tree view without any 3D representation.

But let me go ahead and implement these features and see how it turns out when working with complex models.

[vikasTmz]

The advantage of having these primitives exist in the scene is it would be easy to manage them. But if they are to be managed in a list as just data points, the list would be very large for even a simple model like cubesat and it would be hard for the user then to remove/ disable a random list of points/ lines from the tree view without any 3D representation.

Any reviews on this?

[s-trinh]

Sorry for the delay.

But if they are to be managed in a list as just data points, the list would be very large for even a simple model like cubesat and it would be hard for the user then to remove/ disable a random list of points/ lines from the tree view without any 3D representation.

• the 3D face panel should allow to model only one face
• a tree view box should be a good candidate to display the list of points the user has chosen to model a face, as it is rare to model a face by more than 10 points
• it should be possible to highlight the current selected point in the tree view (link 1, link 2) in the main view

The current status of the pull request for me is:

• it is possible to model multiples geometric primitives (e.g. 2 circles, 3 faces, 4 lines) but each primitive (except for 3D face) have to be a specific object group?
• the last commits introduce the possibility to copy directly the coordinates of the selected point by a click on a button and display the good number of points for circle and cylinder

Is it correct (I don't have access to my dev machine right now) or I missed something? If so, this pull request could be a first Blender plugin.

---

The second plugin I would like to have is:

• one tree view that lists the list of geometric primitives added by the user (for example at the bottom of the current panel)
• 3D circle and 3D cylinder are good but a click to "set propertie" (to be renamed to a more appropriate name like "add") will add the primitive to the primitive tree view
• 3D face panel will have one button to add the selected points in a list, the points will be displayed in another tree view
• 3D line panel will have only two points / 2 buttons to copy the coordinate from the current selected point
• a text box to let the user set a name to the primitive modelled

We should proceed iteratively:

• first version (model primitives, remove a primitive):
  • a tree view to display the list of added primitives (only display the list of primitive and remove, with generic name like face1, circle#1, circle#2, etc.)
  • 3D circle and 3D cylinder with a button to add these primitives
  • 3D line similar to 3D circle and cylinder
  • 3D face: a button to add all the selected points in a list but no display/edit and add directly the primitive in the list of primitives
• second version (edit a primitive):
  • allow the user to edit a primive by selecting it in the primitive tree view and update the corresponding 3D face, line, circle or cylinder panels with the according properties
  • 3D face will display in a tree view the list of points that model the face, visual feedback (highlight the current point) and edition possible
• third version (optional):
  • possibility to set directly the LOD properties and primitive names
  • hierarchical model by changing the "level" of the primitive in the primitive tree view

Do you think it is feasible? In the (global) project, I would like to prioritize on this 2nd Blender plugin. If we are short in time, some optional features could be dropped (for example, import a .cao in Blender) or simplify.

[vikasTmz]

The current status of the pull request for me

Yes, these have been implemented.

I believe I can finish the second plugin (including version 1,2,3) within the given deadlines in my timeline. The import plugin can also be done since I've alloted a week for that during the month of August and also 2 weeks after that to work on any improvements.

[vikasTmz]

There could be one issue with this:

• To get the selected vertices of a mesh in blender, we have to traverse through all the vertices of the mesh and see if the selected flag is true. There is no function call that is triggered on selecting the vertex in the scene.

• So the problem here is that the user will have to make sure that he/she selects the vertices in the order their indices are stored in blender i.e if you look at the screenshot below, the vertices that the user selects to model a face using points have to be selected in their order of their indices such that this order is maintained on traversing through the entire mesh to find the selected vertices.

This is fine for simple models.

• But for a complex model like this:

  it could be difficult to ensure this order. If the user selects the vertices 11080->11081->11120->11091, there is no way of knowing whether 11120 was selected before 11091.

Solution: If the user were to follow the steps I mentioned in the 4 steps few comments above (June 3), this issue can be solved.

[s-trinh]

Ok. Let's move to the tutorial part for now.

[vikasTmz]

I believe I've found a solution to the above. The new PR has the implementation. Basically after the user selects the vertices:

• A new mesh is formed with these vertices.
• Faces/edges are added.
• If polycount > 1: Limited Dissolve is applied.

Therefore all user has to do is to select the vertices and add it as a primitive. Editing these vertices may be tricky, so right now only add/delete is possible.

[s-trinh]

Done in #16