From ad0438849eb1dd3d08a8e2cbc476c84958eff3e7 Mon Sep 17 00:00:00 2001
From: veclavtalica <veclavtalica@poto.cafe>
Date: Tue, 1 Oct 2024 16:10:36 +0300
Subject: [PATCH] twn_fog.c: fog added!

---
 CMakeLists.txt                      |  1 +
 apps/scenery/scenes/ingame.c        |  1 +
 include/twn_rendering.h             |  2 ++
 src/rendering/twn_fog.c             | 34 +++++++++++++++++++++++++++++
 src/rendering/twn_gl_15_rendering.c | 27 +++++++++++++++++++++++
 src/rendering/twn_rendering.c       |  3 +++
 src/rendering/twn_rendering_c.h     |  8 +++++++
 7 files changed, 76 insertions(+)
 create mode 100644 src/rendering/twn_fog.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5786993..6a3c579 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -105,6 +105,7 @@ set(TWN_SOURCE_FILES
         src/rendering/twn_triangles.c
         src/rendering/twn_circles.c
         src/rendering/twn_skybox.c
+        src/rendering/twn_fog.c
 
         # for dynamic load based solution main is compiled in a separate target
         $<$<NOT:$<BOOL:${TWN_FEATURE_DYNLIB_GAME}>>:src/twn_main.c
diff --git a/apps/scenery/scenes/ingame.c b/apps/scenery/scenes/ingame.c
index 2e49be6..5d449a1 100644
--- a/apps/scenery/scenes/ingame.c
+++ b/apps/scenery/scenes/ingame.c
@@ -85,6 +85,7 @@ static void ingame_tick(State *state) {
     }
 
     push_skybox("/assets/miramar/miramar_*.tga");
+    push_fog(0.9, 1.0, 0.05, (Color){ 140, 147, 160, 255 });
 }
 
 
diff --git a/include/twn_rendering.h b/include/twn_rendering.h
index 5cf1740..2028527 100644
--- a/include/twn_rendering.h
+++ b/include/twn_rendering.h
@@ -76,4 +76,6 @@ TWN_API void set_camera(const Camera *camera);
 /* expects '*' masks that will be expanded to 6 names: 'up', 'down', 'east', 'west', 'north' and 'south' */
 TWN_API void push_skybox(const char *paths);
 
+TWN_API void push_fog(float start, float end, float density, Color color);
+
 #endif
diff --git a/src/rendering/twn_fog.c b/src/rendering/twn_fog.c
new file mode 100644
index 0000000..4beec7c
--- /dev/null
+++ b/src/rendering/twn_fog.c
@@ -0,0 +1,34 @@
+#include "twn_rendering.h"
+#include "twn_rendering_c.h"
+#include "twn_util.h"
+
+#include <stdbool.h>
+
+static float start_cache, end_cache, density_cache;
+static Color color_cache;
+static bool fog_used = false;
+
+
+void push_fog(float start, float end, float density, Color color) {
+    start_cache = start;
+    end_cache = end;
+    density_cache = density;
+    color_cache = color;
+    fog_used = true;
+}
+
+
+void apply_fog(void) {
+    if (!fog_used)
+        return;
+
+    finally_apply_fog(start_cache, end_cache, density_cache, color_cache);
+}
+
+
+void pop_fog(void) {
+    if (!fog_used)
+        return;
+
+    finally_pop_fog();
+}
diff --git a/src/rendering/twn_gl_15_rendering.c b/src/rendering/twn_gl_15_rendering.c
index 2fed12b..23fc0f9 100644
--- a/src/rendering/twn_gl_15_rendering.c
+++ b/src/rendering/twn_gl_15_rendering.c
@@ -666,3 +666,30 @@ void finally_render_skybox(char *paths) {
 
     glCallList(list);
 }
+
+
+void finally_apply_fog(float start, float end, float density, Color color) {
+    if (density < 0.0f || density > 1.0f)
+        log_warn("Invalid fog density given, should be in range [0..1]");
+
+    /* TODO: cache it for constant parameters, which is a common case */
+
+    glEnable(GL_FOG);
+
+    glFogf(GL_FOG_DENSITY, density);
+    glFogf(GL_FOG_START, start);
+    glFogf(GL_FOG_END, end);
+
+    float color_conv[4];
+    color_conv[0] = (float)color.r / UINT8_MAX;
+    color_conv[1] = (float)color.g / UINT8_MAX;
+    color_conv[2] = (float)color.b / UINT8_MAX;
+    color_conv[3] = (float)color.a / UINT8_MAX;
+
+    glFogfv(GL_FOG_COLOR, color_conv);
+}
+
+
+void finally_pop_fog(void) {
+    glDisable(GL_FOG);
+}
diff --git a/src/rendering/twn_rendering.c b/src/rendering/twn_rendering.c
index d8443ec..9031df5 100644
--- a/src/rendering/twn_rendering.c
+++ b/src/rendering/twn_rendering.c
@@ -93,11 +93,14 @@ static void render_space(void) {
         return;
 
     use_space_pipeline();
+    apply_fog();
 
     for (size_t i = 0; i < hmlenu(ctx.uncolored_mesh_batches); ++i) {
         draw_uncolored_space_traingle_batch(&ctx.uncolored_mesh_batches[i].value,
                                             ctx.uncolored_mesh_batches[i].key);
     }
+
+    pop_fog();
 }
 
 
diff --git a/src/rendering/twn_rendering_c.h b/src/rendering/twn_rendering_c.h
index 8cbb389..96f072d 100644
--- a/src/rendering/twn_rendering_c.h
+++ b/src/rendering/twn_rendering_c.h
@@ -225,4 +225,12 @@ void render_skybox(void);
 
 void finally_render_skybox(char *paths_in_use);
 
+void apply_fog(void);
+
+void finally_apply_fog(float start, float end, float density, Color color);
+
+void pop_fog(void);
+
+void finally_pop_fog(void);
+
 #endif