audulus / vger-rs

2D GPU renderer for dynamic UIs

vger-rs

vger is a vector graphics renderer which renders a limited set of primitives, but does so almost entirely on the GPU. Port of VGER to Rust. Used in rui.

Status

• ✅ Quadratic bezier strokes
• ✅ Round Rectangles
• ✅ Circles
• ✅ Line segments (need square ends for Audulus)
• ✅ Arcs
• ✅ Text (Audulus only uses one font, but could add support for more if anyone is interested)
• ✅ Multi-line text
• ✅ Path Fills.
• ✅ Scissoring
• ❌ Images

Why?

I was previously using nanovg for Audulus, which was consuming too much CPU for the immediate-mode UI. nanovg is certainly more full featured, but for Audulus, vger maintains 120fps while nanovg falls to 30fps on my 120Hz iPad because of CPU-side path tessellation, and other overhead. vger renders analytically without tessellation, leaning heavily on the fragment shader.

How it works

vger draws one or more quads for each primitive and computes the actual primitive shape in the fragment function with an SDF. For path fills, vger splits paths into horizontal slabs (see path.rs) to reduce the number of tests in the fragment function.

The bezier path fill case is somewhat original. To avoid having to solve quadratic equations (which has numerical issues), the fragment function uses a sort-of reverse Loop-Blinn. To determine if a point is inside or outside, vger tests against the lines formed between the endpoints of each bezier curve, flipping inside/outside for each intersection with a +x ray from the point. Then vger tests the point against the area between the bezier segment and the line, flipping inside/outside again if inside. This avoids the pre-computation of Loop-Blinn, and the AA issues of Kokojima.

References

Text Rendering Hates You

Adventures in Text Rendering

Vector Graphics on GPU

GPU UIs at 120 FPS

vger-rs's Issues

`Vger::stroke_segment` can't handle vertical nor horizontal line segments

The title says it all; such line segments don't get rendered.

See my branch for relevant tests (segment_stroke_horizontal and segment_stroke_vertical).

How does this compare to other vector graphics rendering libraries performance wise?

TLDR

If I may ask, I'm currently using Google's Skia library for vector graphics rendering VIA the skia-safe crate, but I'd love to use a more 'rusty' solution. Do you have any idea how this would compare to Google's Skia library performance wise? As well as other popular rust crates?

Overview

I happen to be in the market for a fast 2D vector graphics rendering library (for my subscript project). Specially for the canvas renderer shown in the image:

All I care about are paths with lines, bezier curves, and fill/stroke support. And I'm kinda interested in rui so I though I'd maybe consider this library...

Edges of shapes are not rendered well

Black rectangle expected to be invisible:

    let black = vger.color_paint(Color{r: 0.0, g: 0.0, b: 0.0, a: 1.0});
    vger.fill_rect(euclid::rect(100.0, 100.0, 100.0, 100.0), 10.0, black);

(5x)

Two rectangles expected to be seamless：

    let cyan = vger.color_paint(Color::CYAN);
    vger.fill_rect(euclid::rect(100.0, 100.0, 100.0, 100.0), 0.0, cyan);
    vger.fill_rect(euclid::rect(200.0, 100.0, 100.0, 100.0), 0.0, cyan);

(5x)

I guess these artifacts are caused by anti-aliasing.

Feature request: opacity groups

Hey! I'm looking to use vger in a project of mine but it doesn't support opacity groups (aka layered transparency). What would it take to add opacity groups to vger? I'd be willing to help implement it. :)

Please only fill circle, no stroke circle, I want to create hollow circles

text is blurry

The tests now write the glyph atlas to a png.

Here's a glyph in the atlas:

here's that glyph rendered:

tests fail on Windows

The tests produce blank images on windows.

Feature request: 3D projection

I'd like to use vger in 3D (and eventually VR) for anti-aliased, GPU-accelerated Bezier rendering. All of the drawing operations would be projected onto a flat 2D plane observed through a 3D perspective camera. Is this possible to implement in vger, and if so, how can I help out?