What tool can generate this kind of illustrations?

Question

I am writing my thesis about 3D modelling, and I found these illustrations in another thesis. I would like to make something similar.

I can already draw the "egg" shapes in Blender, but this "mesh" and the blue and red details are still a mystery to me. For the mesh, I tried the wireframe modifier, but that doesn't seem to be right for many reasons (it has a thickness, and I couldn't find the dotted option).

Obviously a beginner here, not even sure if this was made in Blender. Any tips on how to do it in Blender (or where this could have been drawn) will be welcomed. I'm unfamiliar with the terms, so the nomenclature for the dotted lines and the blue/red/gray areas would also be helpful.

Answer 1

Here is way other than freestyle edge to make this kind of illustration. I used a mix of geometry nodes and blender modifiers and got this result

I will link the file at the end of the post

The sphere's dots and outline are made with geometry nodes

The outline is just the sphere slightly offseted with its normals flipped. The dots are the sphere's edges, that I converted into curves and instanced cubes along these curves. The material needs to have backface culling enabled for the outline to work properly

Here is the node setup :

You can also choose to use sharp edges to control where to put the doted lines

For the red part, you can used a plane, subdivide it and project on the mesh target. I also added a solidify modifier so the backface is visible as well and not occluded by the mesh target.

If you use the outline, set the shrinkwrap modifier snap mode to Above Surface and set the offset to the same value you used for the outline. Then, for the solidify modifier, change the offset to 0 and give it a bit of thickness

For the materials, here is what I used

The sphere material:

The black line material :

The red part material :

Here is the file. Please use blender 4.1 or above for it to work properly

Answer 2

Freestyle in Blender is quite complex and (for me at least) a bit frustrating sometimes because you just do not seem to get lines where you want them :D But to give you a quick idea how you can get something similar like your reference:

Slightly simpler things are not that hard to achieve especially when using the option Mark Freestyle Edge in Edit Mode. For the following example I used three different Freestyle Line Sets, one for the thick external contour, one for the dashed lines of the visible wireframe edges and the last for the thinner, fainter dashed lines of the hidden wireframe:

The material has some alpha transparency to get a bit of that semi-transparent look of your reference. Note however that even the hidden dashed lines will always be overlaid, the material transparency is not necessary for them to be visible.

Also note, although there is a setting where you can have lines on material boundaries, it is not possible to get black outlines along these painted color patches. Freestyle does not detect contours within textures.

For the dashed lines of the wireframe I simply selected all edges in Edit Mode, then Ctrl+E > Mark Freestyle Edge. This way all edges of the base mesh are showing, but all the additional smoothing edges of the Subdivision Surface modifier I put on the object are not visible.

To enable Freestyle, check the option in the Render Properties tab, then you can edit and add line sets in the View Layer Properties tab. The main settings I changed for the three line sets are (by the way lines will be overlaid with the top most line set in front down to the bottom line set in the background):

1. contour:

   Visibility Type > Visible

   Edge Type > External Contour

   Freestyle Thickness > Base Thickness > 10

2. dashed line:

   Visibility Type > Visible

   Edge Type > Edge Mark

   Freestyle Strokes > Dashed Line > Dash 1/Gap 1 > 3

   Freestyle Thickness > Base Thickness > 3

3. dashed line hidden:

   Visibility Type > Hidden

   Edge Type > Edge Mark

   Freestyle Strokes > Dashed Line > Dash 1/Gap 1 > 2

   Freestyle Alpha > Base Transparency > 0.75

   Freestyle Thickness > Base Thickness > 2

The good thing with marking edges as freestyle edges is, no matter how dense a mesh is, you can decide which edges you want to see in a wireframe rendering, like in the example below where all spheres have the same resolution, but different wireframes:

Answer 3

You could project an image onto the surface of your object, the image needs to be on transparent background (PNG format) and you'll plug the Alpha output of the Image Texture node into the Alpha input of the Principled BSDF. The inconvenient of this method is that you'll need to change the thickness of the lines if you don't want them to get thinner towards the poles: