Fixed coordinate scaling

src/render/gpustate.rs

@@ -221,7 +221,7 @@ impl GPUState {
 		// Don't divide by 2, we use this later.
 		let height = s.size / s.pos.z;
 
-		// Width or height, whichever is larger
+		// Width or height, whichever is larger.
 		// Accounts for sprite rotation.
 		let m = height * texture.aspect.max(1.0);
 
@@ -259,9 +259,14 @@ impl GPUState {
 		// After finishing all ops, translate.
 		// This must be done last, all other operations
 		// require us to be at (0, 0).
+		//
+		// Note that we divide camera zoom by two.
+		// THIS IS IMPORTANT!
+		// The height of the viewport is `zoom` in game units,
+		// but it's 2 in screen units! (since coordinates range from -1 to 1)
 		let translate = Matrix4::from_translation(Vector3 {
-			x: pos.x / game.camera.zoom / self.window_aspect,
-			y: pos.y / game.camera.zoom,
+			x: pos.x / (game.camera.zoom / 2.0) / self.window_aspect,
+			y: pos.y / (game.camera.zoom / 2.0),
 			z: 0.0,
 		});
 
@@ -301,15 +306,15 @@ impl GPUState {
 		let screen_aspect = Matrix4::from_nonuniform_scale(1.0 / self.window_aspect, 1.0, 1.0);
 
 		let ptranslate = Matrix4::from_translation(Vector3 {
-			x: parent_pos.x / game.camera.zoom / self.window_aspect,
-			y: parent_pos.y / game.camera.zoom,
+			x: parent_pos.x / (game.camera.zoom / 2.0) / self.window_aspect,
+			y: parent_pos.y / (game.camera.zoom / 2.0),
 			z: 0.0,
 		});
 		let protate = Matrix4::from_angle_z(parent_angle);
 
 		let translate = Matrix4::from_translation(Vector3 {
-			x: s.pos.x / game.camera.zoom / self.window_aspect,
-			y: s.pos.y / game.camera.zoom,
+			x: s.pos.x / (game.camera.zoom / 2.0) / self.window_aspect,
+			y: s.pos.y / (game.camera.zoom / 2.0),
 			z: 0.0,
 		});
 

src/render/shaders/starfield.wgsl

@@ -75,7 +75,6 @@ fn vertex_main(
 	// but not *too* many. We thus scale linearly.
 	let hide_fraction = 1.0 - 1.0 / (zoom_min_times * 0.8);
 
-	// Hide some stars at large zoom levels.
 	if (
 		instance.size < (
 			hide_fraction * (global.starfield_size_limits.y - global.starfield_size_limits.x)
@@ -100,9 +99,11 @@ fn vertex_main(
 	}
 
 
+	// Divide by two, because viewport height is 2 in screen units
+	// (coordinates go from -1 to 1)
 	var pos: vec2<f32> = vec2<f32>(
-		vertex.position.x * scale / global.window_aspect.x,
-		vertex.position.y * scale
+		vertex.position.x * (scale/2.0) / global.window_aspect.x,
+		vertex.position.y * (scale/2.0)
 	);
 
 	// World position relative to camera
@@ -113,7 +114,7 @@ fn vertex_main(
 	// Translate
 	pos = pos + (
 		// Don't forget to correct distance for screen aspect ratio too!
-		(camera_pos / (global.camera_zoom.x * (instance.position.z)))
+		(camera_pos / (global.camera_zoom.x * instance.position.z))
 		/ vec2<f32>(global.window_aspect.x, 1.0)
 	);