trimesh facet shape conversion

[hx2A]

@villares, below is a working example of our trimesh facets code in py5:

import numpy as np
import py5
from trimesh import creation

# %%

WIDTH, HEIGHT = 800, 800

# pay attention to clockwise vs counterclockwise
linestring = np.array(
    [[0.0, 0.0], [100.0, 0.0], [100.0, 100.0], [50.0, 150.0], [0.0, 100.0], [0.0, 0.0]]
) + np.array([[50.0, 0.0]])


def setup():
    global shape
    py5.size(WIDTH, HEIGHT, py5.P3D)

    py5.fill(255)
    py5.stroke(0)
    py5.stroke_weight(3)

    shape = py5.convert_shape(
        creation.revolve(linestring, angle=0.8 * py5.TWO_PI, sections=128, cap=True),
        draw_facets=True,
        facet_min_angle=0.1,
    )


def draw():
    py5.background(204)
    py5.lights()

    py5.translate(py5.width / 2, py5.height / 2, -200)
    py5.rotate_x(py5.frame_count * 0.01)
    py5.rotate_y(py5.frame_count * 0.02)
    py5.rotate_z(py5.frame_count * 0.015)
    py5.scale(2)

    py5.shape(shape)


py5.run_sketch()

The draw_facets kwarg is assumed to be True when facet_min_angle is used, so in the above example draw_facets=True can be omitted and will yield the same result. The facet_min_angle kwarg is assumed to be 0 when draw_facets=True is used but facet_min_angle is not. I think this is a good design choice and considers your thoughts on from discussion thread somewhere.

Do you like the kwarg names?

[villares]

Cool!

I'd have to check again my intuitions about the names and values...

Remind me, what is the result from draw_facets=True (default facet_min_angle=0)? It just cleans/hides the edges embedded in a coplanar region right?

Another complementary vocabulary I've seen in other contexts/software is to talk about the edges not the facets... like hide_edges=True and maybe min_edge_angle. What do you think?

[hx2A]

Remind me, what is the result from draw_facets=True (default facet_min_angle=0)? It just cleans/hides the edges embedded in a coplanar region right?

Right, exactly. This is the nice facet code we used at Python Brasil.

Another complementary vocabulary I've seen in other contexts/software is to talk about the edges not the facets... like hide_edges=True and maybe min_edge_angle. What do you think?

I like min_edge_angle, that is more clear than facet_min_angle. I find hide_edges=True to be confusing, it makes me think it does the equivalent of no_stroke(). How about instead we use something like draw_facet_edges or simply facet_edges? That would pair well with min_edge_angle.

[villares]

I'm glad you like min_edge_angle!

My first thought was something like clean_facet_edges ... I still find draw_facet_edges a bit confusing...
Maybe facet_edges is a good compromise, and it is shorter, I wouldn't mind it :)

But now I remember my first idea... not having two separate kwargs... then if needed you could set min_edge_angle to None and it would turn off the feature... I concede this would be harder to find out.

Yet one more option that doesn't require knowing what a facet is: draw_all_edges (True would means the facet feature is turned off, the opposite of the current kwarg way of setting it).

[hx2A]

My first thought was something like clean_facet_edges ... I still find draw_facet_edges a bit confusing...
Maybe facet_edges is a good compromise, and it is shorter, I wouldn't mind it :)

How about facet_edges and min_edge_angle? And although there are two kwargs, I set it up so that you only need to use one. If you set min_edge_angle to anything it assumes facet_edges is true, and setting facet_edges to true assumes that min_edge_angle is zero. I did it that way because I don't want to have to type min_edge_angle=0, I'd rather only use that kwarg when the angle I want is greater than 0, but it can work that way for people who want it.

[villares]

How about facet_edges and min_edge_angle ?

Yes this would be OK!

What is the general default if no kwarg is passed? Would the facet_edges be True by default?
I like the idea, even if changes the behaviour of previous sketches...

[hx2A]

What is the general default if no kwarg is passed? Would the facet_edges be True by default?
I like the idea, even if changes the behaviour of previous sketches...

The default was facet_edges = False, but after thinking about it for a while, I warmed up to the idea of making the default True. It does look cleaner and it adds more value above the default way of how Processing would render a mesh. After all, if you wanted to render a Trimesh object the way Processing does it with every triangle and py5's convert functionality was not available to you, you'd just need to write code like this:

    shape = sketch.create_shape()
    with shape.begin_shape(sketch.TRIANGLES):
        shape.vertices(obj.vertices[obj.faces.ravel()])