1 files changed, 26 insertions, 11 deletions
diff --git a/wgpu/src/shader/image.wgsl b/wgpu/src/shader/image.wgsl
index 7b2e5238..0eeb100f 100644
--- a/wgpu/src/shader/image.wgsl
+++ b/wgpu/src/shader/image.wgsl
@@ -9,40 +9,55 @@ struct Globals {
 struct VertexInput {
     @builtin(vertex_index) vertex_index: u32,
     @location(0) pos: vec2<f32>,
-    @location(1) scale: vec2<f32>,
-    @location(2) atlas_pos: vec2<f32>,
-    @location(3) atlas_scale: vec2<f32>,
-    @location(4) layer: i32,
+    @location(1) center: vec2<f32>,
+    @location(2) scale: vec2<f32>,
+    @location(3) rotation: f32,
+    @location(4) opacity: f32,
+    @location(5) atlas_pos: vec2<f32>,
+    @location(6) atlas_scale: vec2<f32>,
+    @location(7) layer: i32,
 }
 
 struct VertexOutput {
     @builtin(position) position: vec4<f32>,
     @location(0) uv: vec2<f32>,
     @location(1) layer: f32, // this should be an i32, but naga currently reads that as requiring interpolation.
+    @location(2) opacity: f32,
 }
 
 @vertex
 fn vs_main(input: VertexInput) -> VertexOutput {
     var out: VertexOutput;
 
-    let v_pos = vertex_position(input.vertex_index);
+    // Generate a vertex position in the range [0, 1] from the vertex index.
+    var v_pos = vertex_position(input.vertex_index);
 
+    // Map the vertex position to the atlas texture.
     out.uv = vec2<f32>(v_pos * input.atlas_scale + input.atlas_pos);
     out.layer = f32(input.layer);
+    out.opacity = input.opacity;
 
-    var transform: mat4x4<f32> = mat4x4<f32>(
-        vec4<f32>(input.scale.x, 0.0, 0.0, 0.0),
-        vec4<f32>(0.0, input.scale.y, 0.0, 0.0),
+    // Calculate the vertex position and move the center to the origin
+    v_pos = round(input.pos) + v_pos * input.scale - input.center;
+
+    // Apply the rotation around the center of the image
+    let cos_rot = cos(input.rotation);
+    let sin_rot = sin(input.rotation);
+    let rotate = mat4x4<f32>(
+        vec4<f32>(cos_rot, sin_rot, 0.0, 0.0),
+        vec4<f32>(-sin_rot, cos_rot, 0.0, 0.0),
         vec4<f32>(0.0, 0.0, 1.0, 0.0),
-        vec4<f32>(input.pos, 0.0, 1.0)
+        vec4<f32>(0.0, 0.0, 0.0, 1.0)
     );
 
-    out.position = globals.transform * transform * vec4<f32>(v_pos, 0.0, 1.0);
+    // Calculate the final position of the vertex
+    out.position = globals.transform * (vec4<f32>(input.center, 0.0, 0.0) + rotate * vec4<f32>(v_pos, 0.0, 1.0));
 
     return out;
 }
 
 @fragment
 fn fs_main(input: VertexOutput) -> @location(0) vec4<f32> {
-    return textureSample(u_texture, u_sampler, input.uv, i32(input.layer));
+    // Sample the texture at the given UV coordinate and layer.
+    return textureSample(u_texture, u_sampler, input.uv, i32(input.layer)) * vec4<f32>(1.0, 1.0, 1.0, input.opacity);
 }