diff --git a/src/bin/wireframe/ray.wgsl b/src/bin/wireframe/ray.wgsl
index 2d9362d..a014ed9 100644
--- a/src/bin/wireframe/ray.wgsl
+++ b/src/bin/wireframe/ray.wgsl
@@ -48,7 +48,8 @@ fn vs_main(seg: SegmentInput, off: OffsetInput) -> VertexOutput {
 	default: {}
 	}
 	let pt_cs = camera.mvp * vec4(pt, 1.);
-	let dir_cs = camera.mvp * vec4(dir, 0.);
+	let dir_cs0 = camera.mvp * vec4(dir, 0.);
+	let dir_cs = dir_cs0.xyz * pt_cs.w - pt_cs.xyz * dir_cs0.w;
 	let normal_cs = camera.scale * normalize(vec2(-dir_cs.y, dir_cs.x));
 	out.clip_position = pt_cs + vec4(sgn * width * normal_cs, 0., 0.);
 	return out;