From 19a5cb562cad49fa60e9cef0701746d780d063ca Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Thu, 3 Aug 2023 09:22:54 +0900
Subject: [PATCH] [vulkan] Avoid bsp back-face cull in shadow pass

When rendering shadow maps, all the faces are needed, not just those
facing the pseudo-camera (due to the null-point of the shadow pass
view).
---
 libs/video/renderer/vulkan/rp_main_def.plist |  4 +--
 libs/video/renderer/vulkan/vulkan_bsp.c      | 29 ++++++++++++++++++--
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/libs/video/renderer/vulkan/rp_main_def.plist b/libs/video/renderer/vulkan/rp_main_def.plist
index 2623a883e..e108eb3f2 100644
--- a/libs/video/renderer/vulkan/rp_main_def.plist
+++ b/libs/video/renderer/vulkan/rp_main_def.plist
@@ -1414,9 +1414,9 @@ renderpasses = {
 						color = $color.bsp;
 						tasks = (
 							{ func = bsp_draw_queue;
-							  params = (main, translucent, 2); },
+							  params = (main, translucent, 1); },
 							{ func = bsp_draw_queue;
-							  params = (main, turbulent, 2); },
+							  params = (main, turbulent, 1); },
 						);
 
 						stages = (
diff --git a/libs/video/renderer/vulkan/vulkan_bsp.c b/libs/video/renderer/vulkan/vulkan_bsp.c
index 2ba3fa2a8..05b05fbeb 100644
--- a/libs/video/renderer/vulkan/vulkan_bsp.c
+++ b/libs/video/renderer/vulkan/vulkan_bsp.c
@@ -685,7 +685,7 @@ get_side (const bsp_pass_t *pass, const mnode_t *node)
 }
 
 static inline void
-visit_node (bsp_pass_t *pass, const mnode_t *node, int side)
+visit_node_bfcull (bsp_pass_t *pass, const mnode_t *node, int side)
 {
 	bspctx_t   *bctx = pass->bsp_context;
 	int         c;
@@ -714,6 +714,27 @@ visit_node (bsp_pass_t *pass, const mnode_t *node, int side)
 	}
 }
 
+static inline void
+visit_node_no_bfcull (bsp_pass_t *pass, const mnode_t *node, int side)
+{
+	bspctx_t   *bctx = pass->bsp_context;
+	int         c;
+
+	// chain any visible surfaces on the node that face the camera.
+	// not all nodes have any surfaces to draw (purely a split plane)
+	if ((c = node->numsurfaces)) {
+		const bsp_face_t *face = bctx->faces + node->firstsurface;
+		const int  *frame = pass->face_frames + node->firstsurface;
+		int         vis_frame = pass->vis_frame;
+		for (; c; c--, face++, frame++) {
+			if (*frame != vis_frame)
+				continue;
+
+			chain_surface (face, pass, bctx);
+		}
+	}
+}
+
 static inline int
 test_node (const bsp_pass_t *pass, int node_id)
 {
@@ -725,7 +746,8 @@ test_node (const bsp_pass_t *pass, int node_id)
 }
 
 static void
-R_VisitWorldNodes (bsp_pass_t *pass, vulkan_ctx_t *ctx)
+R_VisitWorldNodes (bsp_pass_t *pass, vulkan_ctx_t *ctx,
+				   void (*visit_node) (bsp_pass_t *, const mnode_t *, int))
 {
 	const mod_brush_t *brush = pass->brush;
 	typedef struct {
@@ -1259,7 +1281,8 @@ bsp_visit_world (const exprval_t **params, exprval_t *result, exprctx_t *ectx)
 	if (pass->instances) {
 		DARRAY_APPEND (&pass->instances[world_id].entities, world_id);
 	}
-	R_VisitWorldNodes (pass, ctx);
+	auto visit_node = pass_ind ? visit_node_no_bfcull : visit_node_bfcull;
+	R_VisitWorldNodes (pass, ctx, visit_node);
 
 	if (r_drawentities) {
 		auto queue = pass->entqueue;