shaders/lightmap: clean up a bit

Note, `chunk_offset` isn't needed because origin is actually expected at
the center of the first tile.

2 files changed, 24 insertions, 11 deletions

diff --git a/shaders/lightmap.cpp b/shaders/lightmap.cpp
index 293e8f2e..c676808e 100644
--- a/shaders/lightmap.cpp
+++ b/shaders/lightmap.cpp
@@ -25,15 +25,26 @@ namespace floormat {
 
 namespace {
 
+template<typename T>
+constexpr T poor_mans_ceil(T x)
+{
+    static_assert(std::is_floating_point_v<T>);
+    const auto x0 = (int64_t)x;
+    if (x > x0)
+        return T(x0 + (int64_t)1);
+    else
+        return x0;
+}
+
+constexpr auto neighbor_count = 4;
 constexpr float fuzz_pixels = 16;
 constexpr float shadow_wall_depth = 8;
 constexpr float real_image_size = 1024;
 
-constexpr auto neighbor_count = lightmap_shader::neighbor_count;
-constexpr auto image_size   = TILE_SIZE2 * TILE_MAX_DIM * neighbor_count;
+constexpr auto half_neighbors = (int)poor_mans_ceil(neighbor_count/2.f);
 
+constexpr auto image_size   = TILE_SIZE2 * TILE_MAX_DIM * neighbor_count;
 constexpr auto chunk_size   = TILE_SIZE2 * TILE_MAX_DIM;
-constexpr auto chunk_offset = TILE_SIZE2/2;
 
 constexpr auto clip_start = Vector2{-1, -1};
 constexpr auto clip_scale = 2/image_size;
@@ -209,7 +220,7 @@ std::array<UnsignedShort, 6> lightmap_shader::quad_indexes(size_t N)
 
 void lightmap_shader::add_light(Vector2 neighbor_offset, const light_s& light)
 {
-    neighbor_offset += half_neighbors;
+    neighbor_offset += Vector2((float)half_neighbors);
 
     constexpr auto tile_size = TILE_SIZE2.sum()/2;
     float range;
@@ -229,7 +240,7 @@ void lightmap_shader::add_light(Vector2 neighbor_offset, const light_s& light)
     range *= tile_size;
     range = std::fmax(0.f, range);
 
-    auto center_fragcoord = light.center + chunk_offset + neighbor_offset * chunk_size; // window-relative coordinates
+    auto center_fragcoord = light.center + neighbor_offset * chunk_size; // window-relative coordinates
     auto center_clip = clip_start + center_fragcoord * clip_scale; // clip coordinates
 
     float alpha = light.color.a() / 255.f;
@@ -286,9 +297,14 @@ GL::Texture2D& lightmap_shader::accum_texture()
     return framebuffer.accum;
 }
 
+int lightmap_shader::iter_bounds()
+{
+    return half_neighbors;
+}
+
 void lightmap_shader::add_rect(Vector2 neighbor_offset, Vector2 min, Vector2 max)
 {
-    auto off = neighbor_offset*chunk_size + chunk_offset;
+    auto off = neighbor_offset*chunk_size;
     min += off;
     max += off;
 
@@ -336,7 +352,7 @@ void lightmap_shader::add_rect(Vector2 neighbor_offset, Pair<Vector2, Vector2> m
 
 void lightmap_shader::add_chunk(Vector2 neighbor_offset, chunk& c)
 {
-    neighbor_offset += half_neighbors;
+    neighbor_offset += Vector2(half_neighbors);
 
     add_geometry(neighbor_offset, c);
     add_entities(neighbor_offset, c);
diff --git a/shaders/lightmap.hpp b/shaders/lightmap.hpp
index 0479a9b3..5bd38069 100644
--- a/shaders/lightmap.hpp
+++ b/shaders/lightmap.hpp
@@ -46,13 +46,10 @@ struct lightmap_shader final : GL::AbstractShaderProgram
     void add_light(Vector2 neighbor_offset, const light_s& light);
     void bind();
     void finish();
+    static int iter_bounds();
 
     GL::Texture2D& accum_texture();
 
-    // todo allow 16 neighbors on new gpu's
-    static constexpr auto neighbor_count = 4;
-    static constexpr auto half_neighbors = Vector2(neighbor_count)/2;
-
     using Position = GL::Attribute<0, Vector3>;
 
 private: