Model Edge Outline

Scripting Issues
1

Many CAD packages have an option to add an outline to models, where the edges are dark lines.

cad_model_outline
cad_model_outline767×536 6.75 KB

I currently have the model, but no outlined edges.
current_render
current_render601×510 2.02 KB

I’ve seen mention of an outline filter here, but I don’t know if that’s the right tool or even where to find an example of that. How should I go about achieving this outline effect?

2

There are a few potential techniques, I think. One might be to write a post-process shader that achieves this effect, perhaps by comparing a given pixel’s depth-value with nearby depth-values.

In addition, I think that the toon shader (see the samples for more on this) has an option to outline models rendered using it.

[edit]

Looking at that CAD screenshot, I wonder whether they’re not generating a wireframe and rendering that over the model, with a slight depth-offset. Note that the back-facing corner-verticals appear over the “top” of the model for a short distance, perhaps due to the depth-offset causing them to be treated as being “in front of” the technically-closer “top”-faces of the model.

1 Like
3

It’s not as easy as it sounds, you need to use different shaders.

http://web.archive.org/web/20120527185124/http://cgg-journal.com/2008-2/06/index.html

4

There is another option:

from panda3d.core import Vec4
from direct.directtools.DirectGeometry import LineNodePath

from direct.showbase.ShowBase import ShowBase

class MyApp(ShowBase):

    def __init__(self):
        ShowBase.__init__(self)

        vertical = LineNodePath(render, colorVec = Vec4(0, 1, 0, 1))
        vertical.setThickness(2)
        vertical.drawLines([((0, 0, -0.25),(0, 0, 0.25))])
        vertical.create()
        vertical.reparentTo(render)

app = MyApp()
app.run()

If you are using shaders, you will still need to create an algorithm to draw the desired edges. Therefore, you can immediately mark the desired edges with a line.

There are still LineSegs, but I don’t know what

2 Likes
5

@Thaumaturge @serega-kkz Thank you both for your replies. I’m still very new to Panda3D and 3D rendering, so I’m learning as I go. I may give the toon shader a look, but eventually I would like to highlight faces, edges and vertices when the mouse cursor hovers over them, so maybe drawing the lines manually makes the most sense. That way I have more control over how they’re displayed.

1 Like