From a59a6e099459c311ee974c77fc362e5cdaced75a Mon Sep 17 00:00:00 2001
From: "francis.nowak1@gmail.com" <you@example.com>
Date: Sat, 3 May 2025 14:33:47 +0200
Subject: [PATCH] A simple wireframe object that takes a CpuMesh, for use in
 debugging.

Unfortunately, this approach has some limitations: meshes with shared vertices will not be displayed correctly.
---
 src/renderer/object.rs           |   5 +-
 src/renderer/object/wireframe.rs | 158 +++++++++++++++++++++++++++++++
 2 files changed, 162 insertions(+), 1 deletion(-)
 create mode 100644 src/renderer/object/wireframe.rs

diff --git a/src/renderer/object.rs b/src/renderer/object.rs
index 7b53262f6..7f609650a 100644
--- a/src/renderer/object.rs
+++ b/src/renderer/object.rs
@@ -17,7 +17,6 @@ macro_rules! impl_object_body {
         }
     };
 }
-
 mod gm;
 #[doc(inline)]
 pub use gm::*;
@@ -54,6 +53,10 @@ mod axes;
 #[doc(inline)]
 pub use axes::*;
 
+mod wireframe;
+#[doc(inline)]
+pub use wireframe::*;
+
 use crate::core::*;
 use crate::renderer::*;
 
diff --git a/src/renderer/object/wireframe.rs b/src/renderer/object/wireframe.rs
new file mode 100644
index 000000000..94115cf50
--- /dev/null
+++ b/src/renderer/object/wireframe.rs
@@ -0,0 +1,158 @@
+use crate::core::*;
+use crate::renderer::*;
+
+pub struct Wireframe{
+    width: f32,
+    positions: VertexBuffer<Vec3>,
+    barycentric: VertexBuffer<Vec3>,
+    context:  Context,
+    aabb: AxisAlignedBoundingBox,
+    transformation: Mat4,
+}
+impl Wireframe {
+    pub fn new(context: &Context, mesh: &CpuMesh, width: f32) -> Self {
+        let positions = VertexBuffer::new_with_data(
+            context,
+            &mesh.positions.to_f32()
+        );
+        let barycentric = VertexBuffer::new_with_data(
+            context,
+            &(0..positions.count()/3).flat_map(|_| [
+                vec3(1., 0., 0.),
+                vec3(0., 1., 0.),
+                vec3(0., 0., 1.),
+            ]).collect::<Vec<_>>()
+        );
+        Self {
+            width,
+            positions,
+            barycentric,
+            context: context.clone(),
+            aabb: mesh.compute_aabb(),
+            transformation: Mat4::identity(),
+        }
+    }
+    pub fn transform_mut(&mut self) -> &mut Mat4 {
+        &mut self.transformation
+    }
+    pub fn line_width_mut(&mut self) -> &mut f32 {
+        &mut self.width
+    }
+}
+
+struct WireframeMaterial(f32);
+
+impl Object for Wireframe {
+    fn render(&self, viewer: &dyn Viewer, lights: &[&dyn Light]) {
+        render_with_material(&self.context, viewer, &self, WireframeMaterial(self.width), lights);
+    }
+
+    fn material_type(&self) -> MaterialType {
+        WireframeMaterial(0.).material_type()
+    }
+}
+
+impl Material for WireframeMaterial {
+    fn fragment_shader_source(&self, lights: &[&dyn Light]) -> String {
+        r#"
+layout (location = 0) out vec4 outColor;
+
+uniform float u_line_width = 0.5;
+
+in vec3 bary;
+in vec3 pos;
+
+void main() {
+    vec3 d = fwidth(bary);
+    vec3 f = step(d * u_line_width, bary);
+    float b = min(min(f.x, f.y), f.z);
+    outColor = vec4(1.-b);
+}
+            "#.into()
+    }
+
+    fn id(&self) -> EffectMaterialId {
+        //TODO!
+        EffectMaterialId(0)
+    }
+
+    fn use_uniforms(&self, program: &Program, viewer: &dyn Viewer, lights: &[&dyn Light]) {
+        program.use_uniform("u_line_width", self.0);
+    }
+
+    fn render_states(&self) -> RenderStates {
+        RenderStates {
+            depth_test: DepthTest::Always,
+            blend: Blend::TRANSPARENCY,
+            cull: Cull::None,
+            ..Default::default()
+        }
+    }
+
+    fn material_type(&self) -> MaterialType {
+        MaterialType::Transparent
+    }
+}
+
+impl Geometry for Wireframe {
+    fn draw(&self, viewer: &dyn Viewer, program: &Program, render_states: RenderStates) {
+        program.use_uniform("viewProjection", viewer.projection() * viewer.view());
+        program.use_uniform("modelMatrix", self.transformation);
+        program.use_vertex_attribute("position", &self.positions);
+        program.use_vertex_attribute("barycentric", &self.barycentric);
+        program.draw_arrays(
+            render_states,
+            viewer.viewport(),
+            self.positions.count(),
+        );
+    }
+
+    fn vertex_shader_source(&self) -> String {
+        r#"
+uniform mat4 viewProjection;
+uniform mat4 modelMatrix;
+
+in vec3 position;
+in vec3 barycentric;
+
+out vec3 pos;
+out vec3 bary;
+
+void main() {
+    vec4 worldPos = modelMatrix * vec4(position, 1.);
+    pos = worldPos.xyz;
+    bary = barycentric;
+    gl_Position = viewProjection * worldPos;
+}
+        "#.into()
+    }
+
+    fn id(&self) -> GeometryId {
+        //TODO!
+        GeometryId(0)
+    }
+
+    fn render_with_material(
+        &self,
+        _material: &dyn Material,
+        _viewer: &dyn Viewer,
+        _lights: &[&dyn Light],
+    ) {
+        panic!("Wireframes must be rendered with the built-in material.");
+    }
+
+    fn render_with_effect(
+        &self,
+        _material: &dyn Effect,
+        _viewer: &dyn Viewer,
+        _lights: &[&dyn Light],
+        _color_texture: Option<ColorTexture>,
+        _depth_texture: Option<DepthTexture>,
+    ) {
+        panic!("Wireframes do not support effects.");
+    }
+
+    fn aabb(&self) -> AxisAlignedBoundingBox {
+        self.aabb.transformed(self.transformation)
+    }
+}