shaders: use exact value for foreshortening factor

2 files changed, 5 insertions, 3 deletions

diff --git a/shaders/shader.hpp b/shaders/shader.hpp
index 06bf2928..79ceb940 100644
--- a/shaders/shader.hpp
+++ b/shaders/shader.hpp
@@ -66,14 +66,16 @@ constexpr Math::Vector2<T> tile_shader::project(const Math::Vector3<T>& pt)
 {
     static_assert(std::is_floating_point_v<T>);
     const auto x = pt[0], y = pt[1], z = -pt[2];
-    return { x-y, (x+y+z*2)*T(.59) };
+    return { x-y, (x+y+z*2)*T(foreshortening_factor) };
 }
 
 template<typename T>
 constexpr Math::Vector2<T> tile_shader::unproject(const Math::Vector2<T>& px)
 {
+    static_assert(std::is_floating_point_v<T>);
     const auto X = px[0], Y = px[1];
-    return { X + 100 * Y / 59, 100 * Y / 59 - X };
+    const auto Y_ = Y / T(foreshortening_factor);
+    return { X + Y_, Y_ - X };
 }
 
 } // namespace floormat
diff --git a/shaders/shader.vert b/shaders/shader.vert
index a539ed6b..9190fe8d 100644
--- a/shaders/shader.vert
+++ b/shaders/shader.vert
@@ -10,6 +10,6 @@ noperspective out vec2 frag_texcoords;
 
 void main() {
     float x = -position.y, y = -position.x, z = position.z;
-    gl_Position = vec4((x-y+offset.x)*scale.x, ((x+y+z*2)*.59-offset.y)*scale.y, offset.z + depth, 1);
+    gl_Position = vec4((x-y+offset.x)*scale.x, ((x+y+z*2)*0.578125-offset.y)*scale.y, offset.z + depth, 1);
     frag_texcoords = texcoords;
 }