Fix width of lines when zooming

src/render/render_state.rs

@@ -1,3 +1,4 @@
+use cgmath::num_traits::Pow;
 use cgmath::Matrix4;
 use std::collections::HashSet;
 use std::default::Default;
@@ -354,6 +355,11 @@ impl RenderState {
     // TODO: What is StagingBelt for?
     pub fn upload_tile_geometry(&mut self, scheduler: &mut IOScheduler) {
         let visible_z = self.visible_z();
+
+        // Factor which determines how much we need to adjust the width of lines for example.
+        // If zoom == z -> zoom_factor == 1
+        let zoom_factor = 2.0_f64.powf(visible_z as f64 - self.zoom) as f32;
+
         let view_region = self
             .camera
             .view_region_bounding_box(&self.perspective)
@@ -392,7 +398,7 @@ impl RenderState {
             self.buffer_pool.update_tile_metadata(
                 &self.queue,
                 entry,
-                ShaderTileMetadata::new(transform.into()),
+                ShaderTileMetadata::new(transform.into(), zoom_factor),
             );
         }
 
@@ -459,7 +465,7 @@ impl RenderState {
                                     *coords,
                                     style_layer.clone(),
                                     buffer,
-                                    ShaderTileMetadata::new(transform.into()),
+                                    ShaderTileMetadata::new(transform.into(), zoom_factor),
                                     &feature_metadata,
                                 );
                             }

src/render/shaders/mod.rs

@@ -137,6 +137,11 @@ pub mod tile {
                         format: wgpu::VertexFormat::Float32x4,
                         shader_location: 7,
                     },
+                    wgpu::VertexAttribute {
+                        offset: 4 * wgpu::VertexFormat::Float32x4.size(),
+                        format: wgpu::VertexFormat::Float32,
+                        shader_location: 9,
+                    },
                 ],
             },
             // vertex style
@@ -302,10 +307,14 @@ pub struct ShaderFeatureStyle {
 #[derive(Copy, Clone, Pod, Zeroable)]
 pub struct ShaderTileMetadata {
     pub transform: Mat4x4f32,
+    pub zoom_factor: f32,
 }
 
 impl ShaderTileMetadata {
-    pub fn new(transform: Mat4x4f32) -> Self {
+    pub fn new(transform: Mat4x4f32, zoom_factor: f32) -> Self {
-        Self { transform }
+        Self {
+            transform,
+            zoom_factor,
+        }
     }
 }

src/render/shaders/tile.vertex.wgsl

@@ -23,10 +23,11 @@ fn main(
     [[location(6)]] translate3: vec4<f32>,
     [[location(7)]] translate4: vec4<f32>,
     [[location(8)]] color: vec4<f32>,
+    [[location(9)]] zoom_factor: f32,
     [[builtin(instance_index)]] instance_idx: u32 // instance_index is used when we have multiple instances of the same "object"
 ) -> VertexOutput {
     let z = 0.0;
-    let width = 2.0;
+    let width = 3.0 * zoom_factor;
 
     // The following code moves all "invisible" vertices to (0, 0, 0)
     //if (color.w == 0.0) {