From 42b5f1997cdd5e99645e24dca6cb89cc7b081a09 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Sat, 1 Nov 2025 18:23:08 -0700
Subject: Add support for alpha mode

---
 src/render/renderer.c | 46 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 40 insertions(+), 6 deletions(-)

(limited to 'src/render/renderer.c')

diff --git a/src/render/renderer.c b/src/render/renderer.c
index b513ed4..26b63bc 100644
--- a/src/render/renderer.c
+++ b/src/render/renderer.c
@@ -86,12 +86,13 @@ static ShaderProgram* load_shader(Renderer* renderer, RenderSceneMode mode) {
 // }
 
 typedef struct RenderState {
-  GfxCore*       gfxcore;
-  LLR*           llr;
-  Renderer*      renderer;
-  ShaderProgram* shader; // Null to use scene shaders.
-  const Scene*   scene;
-  const Anima*   anima;
+  GfxCore*          gfxcore;
+  LLR*              llr;
+  Renderer*         renderer;
+  ShaderProgram*    shader; // Null to use scene shaders.
+  const Scene*      scene;
+  const Anima*      anima;
+  RenderSceneFilter filter;
 } RenderState;
 
 static void draw_children(
@@ -153,6 +154,24 @@ static void draw_recursively(
         continue;
       }
 
+      // Filter out by material.
+      const Material* material = mesh->material;
+      if (material) {
+        const AlphaMode mode = material->alpha_mode;
+        switch (state->filter) {
+        case RenderOpaqueAndAlphaMasked:
+          if (mode == Blend) {
+            continue;
+          }
+          break;
+        case RenderTransparent:
+          if (mode != Blend) {
+            continue;
+          }
+          break;
+        }
+      }
+
       // TODO: Here we would frustum-cull the mesh. The AABB would have to be
       //  transformed by the model matrix. Rotation would make the AABB
       //  relatively large, but still, the culling would be conservative.
@@ -208,6 +227,20 @@ void gfx_render_scene(Renderer* renderer, const RenderSceneParams* params) {
 
   gfx_llr_set_camera(renderer->llr, camera);
   gfx_llr_set_aspect(renderer->llr, aspect);
+  // TODO: Render Opaque and Mask alpha-mode materials first, then Blend ones.
+  // TODO: I'm not sure if this belongs to the scene renderer per se, or if it
+  //  is something that should be driven from the outside. Specifically, the
+  //  caller could pass in a filter that determines what objects to render. The
+  //  filter could include alpha mode.
+  //  This caller would be some component that understands render passes and
+  //  potentially renders the scene multiple times as needed. For example, a
+  //  depth-prepass, followed by G-buffer, followed by some post-processing,
+  //  etc. Rename this renderer to scene_renderer?
+  // Opaque.
+  state.filter = RenderOpaqueAndAlphaMasked;
+  draw_recursively(&state, mat4_id(), gfx_get_scene_root(scene));
+  // Transparent.
+  state.filter = RenderTransparent;
   draw_recursively(&state, mat4_id(), gfx_get_scene_root(scene));
 }
 
@@ -236,6 +269,7 @@ static void update_rec(SceneNode* node, const Camera* camera, R t) {
   }
 }
 
+// TODO: Move this outside the renderer.
 void gfx_update(Scene* scene, const Camera* camera, R t) {
   assert(scene);
   assert(camera);
-- 
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