rtx: fix translucent things casting shadows (they shouldn't for now)

ref_vk/shaders/ray.rgen

@@ -298,7 +298,7 @@ void main() {
 		const uint sbt_stride = 0;
 		const uint miss_index = 0;
 		const float L = 10000.;
-		traceRayEXT(tlas, flags, GEOMETRY_BIT_OPAQUE,
+		traceRayEXT(tlas, flags, GEOMETRY_BIT_OPAQUE | GEOMETRY_BIT_REFRACTIVE,
 			sbt_offset, sbt_stride, miss_index,
 			origin, 0., direction, L,
 			PAYLOAD_LOCATION_OPAQUE);

ref_vk/shaders/ray_interop.h

@@ -23,6 +23,7 @@ layout (constant_id = 3) const uint MAX_VISIBLE_SURFACE_LIGHTS = 255;
 
 #define GEOMETRY_BIT_OPAQUE 0x01
 #define GEOMETRY_BIT_ADDITIVE 0x02
+#define GEOMETRY_BIT_REFRACTIVE 0x04
 
 #define SHADER_OFFSET_MISS_REGULAR 0
 #define SHADER_OFFSET_MISS_SHADOW 1

ref_vk/vk_ray_internal.h

@@ -34,6 +34,8 @@ typedef struct {
 	enum {
 		MaterialMode_Opaque,
 		MaterialMode_Opaque_AlphaTest,
+		MaterialMode_Refractive,
+		// TODO MaterialMode_Subtractive,
 		MaterialMode_Additive,
 	} material_mode;
 } vk_ray_draw_model_t;

ref_vk/vk_ray_model.c

@@ -339,7 +339,7 @@ void VK_RayFrameAddModel( vk_ray_model_t *model, const vk_render_model_t *render
 		case kRenderTransColor:
 		case kRenderTransTexture:
 			HACK_reflective = true;
-			draw_model->material_mode = MaterialMode_Opaque_AlphaTest; // FIXME add new translucency mode
+			draw_model->material_mode = MaterialMode_Refractive;
 			break;
 
 		// Additive blending: C = SRC * alpha + DST

ref_vk/vk_rtx.c

@@ -523,6 +523,10 @@ static void prepareTlas( VkCommandBuffer cmdbuf ) {
 					inst[i].instanceShaderBindingTableRecordOffset = SHADER_OFFSET_HIT_ALPHA_TEST,
 					inst[i].flags = VK_GEOMETRY_INSTANCE_FORCE_NO_OPAQUE_BIT_KHR;
 					break;
+				case MaterialMode_Refractive:
+					inst[i].mask = GEOMETRY_BIT_REFRACTIVE;
+					inst[i].flags = VK_GEOMETRY_INSTANCE_FORCE_OPAQUE_BIT_KHR;
+					break;
 				case MaterialMode_Additive:
 					inst[i].mask = GEOMETRY_BIT_ADDITIVE;
 					inst[i].instanceShaderBindingTableRecordOffset = SHADER_OFFSET_HIT_ADDITIVE,