[vulkan] Use OIT to visualize the light hulls

Using the translucency pass made it easy to have depth-tested
translucent "solid" light volumes instead of always visible lines (which
are still an option as that's useful too). Most importantly, being able
to see the surfaces helped no end in figuring out that my hulls were
created with counter-clockwise windings instead of quake's usual
clockwise windings and thus my hulls were being rendered inside-out in
the occlusion pass.

libs/video/renderer/Makemodule.am

@@ -349,6 +349,8 @@ light_splatf_src = $(vkshaderpath)/light_splat.frag
 light_splatf_c = $(vkshaderpath)/light_splat.frag.spvc
 light_debug_src = $(vkshaderpath)/light_debug.frag
 light_debug_c = $(vkshaderpath)/light_debug.frag.spvc
+light_oit_src = $(vkshaderpath)/light_oit.frag
+light_oit_c = $(vkshaderpath)/light_oit.frag.spvc
 lighting_cascadef_src = $(vkshaderpath)/lighting_cascade.frag
 lighting_cascadef_c = $(vkshaderpath)/lighting_cascade.frag.spvc
 lighting_cubef_src = $(vkshaderpath)/lighting_cube.frag
@@ -459,6 +461,8 @@ $(light_splatf_c): $(light_splatf_src) $(lighting_h)
 
 $(light_debug_c): $(light_debug_src) $(lighting_h)
 
+$(light_oit_c): $(light_oit_src) $(lighting_h)
+
 $(lighting_nonef_c): $(lighting_nonef_src) $(lighting_h) $(lighting_main)
 
 $(lighting_cascadef_c): $(lighting_cascadef_src) $(lighting_h) $(lighting_main)
@@ -534,6 +538,7 @@ vkshader_c = \
 	$(light_splatv_c) \
 	$(light_splatf_c) \
 	$(light_debug_c) \
+	$(light_oit_c) \
 	$(lighting_cascadef_c) \
 	$(lighting_cubef_c) \
 	$(lighting_nonef_c) \
@@ -630,6 +635,7 @@ EXTRA_DIST += \
 	$(light_splatv_src) \
 	$(light_splatf_src) \
 	$(light_debug_src) \
+	$(light_oit_src) \
 	$(lighting_cascadef_src) \
 	$(lighting_cubef_src) \
 	$(lighting_main) \

libs/video/renderer/vulkan/rp_main_def.plist

@@ -666,6 +666,11 @@ properties = {
 				name = main;
 				module = $builtin/light_debug.frag;
 			};
+			debug_oit = {
+				stage = fragment;
+				name = main;
+				module = $builtin/light_oit.frag;
+			};
 		};
 		vertexInput_splat = {
 			bindings = (
@@ -694,6 +699,9 @@ properties = {
 		splat_layout = {
 			descriptorSets = (matrix_set, lighting_lights);
 		};
+		splat_oit_layout = {
+			descriptorSets = (matrix_set, lighting_lights, oit_set);
+		};
 		layout = {
 			descriptorSets = (shadowmat_set, lighting_lights,
 							  lighting_attach, lighting_shadow);
@@ -1656,6 +1664,27 @@ renderpasses = {
 						inputAssembly = $particle.inputAssembly;
 						layout = $particle.layout.draw;
 					};
+					debug_lights = {
+						@inherit = $compose_base;
+						disabled = true;
+
+						color = $color.lights;
+						tasks = (
+							{ func = lighting_bind_descriptors;
+							  params = (hull, plane); },
+							{ func = lighting_draw_splats; },
+						);
+
+						stages = (
+							$lighting.shader.vertex_splat,
+							$lighting.shader.debug_oit,
+						);
+						vertexInput = $lighting.vertexInput_splat;
+						inputAssembly = $lighting.inputAssembly;
+						layout = $lighting.splat_oit_layout;
+						rasterization = $counter_cw_cull_back;
+						depthStencil = $depth_test_only;
+					};
 				};
 			};
 			gbuffer = {

libs/video/renderer/vulkan/shader.c

@@ -103,6 +103,8 @@ static
 static
 #include "libs/video/renderer/vulkan/shader/light_debug.frag.spvc"
 static
+#include "libs/video/renderer/vulkan/shader/light_oit.frag.spvc"
+static
 #include "libs/video/renderer/vulkan/shader/lighting_cascade.frag.spvc"
 static
 #include "libs/video/renderer/vulkan/shader/lighting_cube.frag.spvc"
@@ -184,6 +186,7 @@ static shaderdata_t builtin_shaders[] = {
 	{ "light_splat.vert", light_splat_vert, sizeof (light_splat_vert) },
 	{ "light_splat.frag", light_splat_frag, sizeof (light_splat_frag) },
 	{ "light_debug.frag", light_debug_frag, sizeof (light_debug_frag) },
+	{ "light_oit.frag", light_oit_frag, sizeof (light_oit_frag) },
 	{ "lighting_cascade.frag", lighting_cascade_frag,
 		sizeof (lighting_cascade_frag) },
 	{ "lighting_cube.frag", lighting_cube_frag, sizeof (lighting_cube_frag) },

libs/video/renderer/vulkan/shader/light_oit.frag

@@ -0,0 +1,16 @@
+#version 450
+#extension GL_GOOGLE_include_directive : enable
+#extension GL_EXT_multiview : enable
+
+#include "oit_store.finc"
+
+layout (location = 0) flat in uint light_index;
+
+layout(early_fragment_tests) in;
+
+void
+main (void)
+{
+	vec4 c = !gl_FrontFacing ? vec4 (1, 0, 1, 0.05) : vec4 (0, 1, 1, 0.05);
+	StoreFrag (c, gl_FragCoord.z);
+}

libs/video/renderer/vulkan/vulkan_lighting.c

@@ -60,6 +60,7 @@
 #include "QF/Vulkan/qf_lighting.h"
 #include "QF/Vulkan/qf_matrices.h"
 #include "QF/Vulkan/qf_texture.h"
+#include "QF/Vulkan/qf_translucent.h"
 #include "QF/Vulkan/barrier.h"
 #include "QF/Vulkan/buffer.h"
 #include "QF/Vulkan/debug.h"
@@ -979,12 +980,14 @@ lighting_bind_descriptors (const exprval_t **params, exprval_t *result,
 	auto stage = *(int *) params[1]->value;
 
 	if (stage == lighting_hull) {
+		bool planes = shadow_type == ST_PLANE;
 		VkDescriptorSet sets[] = {
 			Vulkan_Matrix_Descriptors (ctx, ctx->curFrame),
 			lframe->lights_set,
+			planes ? Vulkan_Translucent_Descriptors (ctx, ctx->curFrame) : 0,
 		};
 		dfunc->vkCmdBindDescriptorSets (cmd, VK_PIPELINE_BIND_POINT_GRAPHICS,
-										layout, 0, 2, sets, 0, 0);
+										layout, 0, 2 + planes, sets, 0, 0);
 
 		VkBuffer buffers[] = {
 			lframe->id_buffer,