https://github.com/shanecelis/bevy_wireframe

https://github.com/shanecelis/bevy_wireframe

Last synced: 26 days ago
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• Host: GitHub
• URL: https://github.com/shanecelis/bevy_wireframe
• Owner: shanecelis
• Created: 2024-05-05T09:43:24.000Z (8 months ago)
• Default Branch: master
• Last Pushed: 2024-06-06T06:07:23.000Z (7 months ago)
• Last Synced: 2024-10-29T00:44:12.938Z (2 months ago)
• Language: Rust
• Size: 3.03 MB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# bevy_wireframe

This repo's aspiration is to provide a wireframe plugin for bevy based on this

[paper](docs/[email protected]). 

## TODO

- [X] Ask for assistance in #rendering on Bevy's [discord](https://bevyengine.org/community/).

- [ ] Determine where to plug into graphics pipeline.

- [ ] Convert GLSL to WGSL.

- [ ] Create render graph node.

- [ ] Create plugin.

## GLSL Code

The paper provides the following GLSL code. The sticking point for us it uses a

geometry shader, which aren't supported in WGSL. So we'd like to probably run a

compute shader that will compute a `dist` attribute on the vertices that will be

accessible on in the fragment shader.

``` glsl

// ------------------ Vertex Shader ---------------------------------- #version 120

#extension GL_EXT_gpu_shader4 : enable

void main(void)

{

    gl_Position = ftransform();

}

// ------------------ Geometry Shader -------------------------------- #version 120

#extension GL_EXT_gpu_shader4 : enable

uniform vec2 WIN_SCALE;

noperspective varying vec3 dist;

void main(void)

{

    vec2 p0 = WIN_SCALE * gl_PositionIn[0].xy/gl_PositionIn[0].w;

    vec2 p1 = WIN_SCALE * gl_PositionIn[1].xy/gl_PositionIn[1].w;

    vec2 p2 = WIN_SCALE * gl_PositionIn[2].xy/gl_PositionIn[2].w;

    vec2 v0 = p2-p1;

    vec2 v1 = p2-p0;

    vec2 v2 = p1-p0;

    float area = abs(v1.x*v2.y - v1.y * v2.x);

    dist = vec3(area/length(v0),0,0);

    gl_Position = gl_PositionIn[0];

    EmitVertex();

    dist = vec3(0,area/length(v1),0);

    gl_Position = gl_PositionIn[1];

    EmitVertex();

    dist = vec3(0,0,area/length(v2));

    gl_Position = gl_PositionIn[2];

    EmitVertex();

    EndPrimitive();

}

// ------------------ Fragment Shader -------------------------------- #version 120

#extension GL_EXT_gpu_shader4 : enable

noperspective varying vec3 dist;

const vec4 WIRE_COL = vec4(1.0,0.0,0.0,1); const vec4 FILL_COL = vec4(1,1,1,1);

void main(void)

{

    float d = min(dist[0],min(dist[1],dist[2]));

    float I = exp2(-2*d*d);

    gl_FragColor = I*WIRE_COL + (1.0 - I)*FILL_COL;

}

```

## References

- J. Andreas Bærentzen, Steen Lund Nielsen, Mikkel Gjøl, and Bent D. Larsen.

  2008. [Two methods for antialiased wireframe drawing with hidden line

  removal.](docs/[email protected]) In Proceedings of the 24th Spring

  Conference on Computer Graphics (SCCG '08). Association for Computing

  Machinery, New York, NY, USA, 171–177. https://doi.org/10.1145/1921264.1921300