creating an empty/hollow Rectangle

[MrAliSalehi]

lets say i have something like this:

let gm: Gm<Rectangle, ColorMaterial> = Gm::new(Rectangle::new(&three_d_backend.context,
                                                                     vec2(0.0,0.0),radians(0.0),200.0,200.0),
                                                 Default::default());

i want the rectange to be empty, in other words I only need the borders to be visible, I could just draw 4 lines connected to each other but that would be a bit complex and much more pain in the ass, Is there a solution to this? thanks

[coderedart]

There will be many ways to do this depending on what you want.

are you going to draw anything behind the rectangle? If not, then just draw a rectangle. set a clip rect to be just a little bit smaller than the previous rectangle. clear color.

If you want a 3D rect transformed by camera, keep a "scratch" texture aside. do the same rect -> clip rect -> clear thing in that texture, and then render that texture into the main framebuffer like a normal two triangled mesh. This will make sure that anything drawn behind the rect will also survive.

If the rectangle is 2D, then its probably better to use a gui paint library. egui provides you a painter that can draw a rect (idk if its hollow inside though) or "path" (lines). https://docs.rs/egui/latest/egui/struct.Painter.html#method.rect_stroke

If you will be doing these kinds of things a lot, then, its better to embed a dedicated vector graphics library like egui's epaint, femtovg or even the greatest of them all SKIA . https://fiddle.skia.org/c/@Canvas_drawIRect .

[MrAliSalehi]

shapes are going to be infront of another view/graphic, thats why they have to be "hollow"
I understood some part of your explanation but im not sure

rect -> clip rect -> clear thing in that texture, and then render that texture into the main framebuffer

no idea

[coderedart]

@MrAliSalehi do you want to draw 3D or 2D shapes? epaint/femtovg/skia can only draw 2D shapes.

[coderedart]

you should have joined rust gamedev discord 10 hours ago :)

Anyway, it really depends on what you are trying to do. If you want to learn graphics programming (eg: opengl + rendering techniques + shaders), it makes a lot of sense to use three-d + rust. otherwise, you are just wasting your time here. three-d, while providing higher level rendering, still requires some knowledge of rendering to use correctly.

If you are not trying to learn graphics programming, and instead want to draw stuff, then you should switch to a much higher level renderer like https://threejs.org/ if you are on web. or a game engine like Godot. if you know python, even https://github.com/pygfx/pygfx is a decent option.

Again, if you want to learn graphics, join the discord server and prepare for a long journey

[MrAliSalehi]

well i actually joined the discord server and asked my question.
Im trying to draw stuff but I cant use high level languages like js or python because the performance is critical, I wrote the same app in C# and it wasn't fast and performant enough so i switched to Rust.
and unfortunately I couldn't find a proper tutorial for graphics and stuff in rust or its libraries.
for example I have no idea what these number are corresponding to:

m.positions = Positions::F32(vec![Vec3::new(-2.0, -2.0, 0.0,),
                                  Vec3::new(2.0, -2.0, 0.0,),
                                  Vec3::new(2.0, 2.0, 0.0,),
                                  Vec3::new(-2.0, 2.0, 0.0)]);

which one is which dimension...ETC

this is what I came up with just now:

let rect = Rect::from_min_max(Pos2::new(0.0, 0.0), Pos2::new(100.0, 100.0));

let a = Shape::Rect(RectShape::stroke(rect, Rounding::from(3.0), Stroke::new(3.0, Color32::from_rgb(255, 0, 0))));

let res =tessellate_shapes(2.0, TessellationOptions::default(), [12, 20], vec![], vec![ClippedShape { shape: a, clip_rect: rect }]);
three_d.glow_backend.render_egui(res, TexturesDelta::default(),
                                 [three_d.glow_backend.framebuffer_size[0] as _, three_d.glow_backend.framebuffer_size[1] as _]);

but then this happened:
thread 'main' panicked at 'managed texture cannot be found'\egui_render_glow-0.5.2\src\lib.rs:420:34
no idea lol

[coderedart]

I will join you on discord

[MrAliSalehi]

thank you

[asny]

Thanks for answering and helping out 🙏 I just want to add that the 'wireframe' example renders instanced cylinders at the edge of triangles which might also be a relevant solution for drawing the edges of a rectangle (it's a bit hard to know exactly what you want to achieve).