rt: don't culling c/cw triangles to fix shadow leaks

de_cbble contains a bunch of floating boxes, which makes sunlight leak if internal back-facing surfaces are culled.

Generally, we should not be culling ray traced triangles (unless absolutely necessary for correctness), as it makes the shader perform additional unnecessary checks.

Try disabling culling universally and see whether it breaks anything.

ref/vk/shaders/bounce.comp

@@ -52,7 +52,7 @@ void readNormals(ivec2 uv, out vec3 geometry_normal, out vec3 shading_normal) {
 bool getHit(vec3 origin, vec3 direction, inout RayPayloadPrimary payload) {
 	rayQueryEXT rq;
 	const uint flags = 0
-		| gl_RayFlagsCullFrontFacingTrianglesEXT
+		//| gl_RayFlagsCullFrontFacingTrianglesEXT
 		//| gl_RayFlagsOpaqueEXT
 		//| gl_RayFlagsTerminateOnFirstHitEXT
 		//| gl_RayFlagsSkipClosestHitShaderEXT

ref/vk/shaders/light_common.glsl

@@ -29,6 +29,10 @@ uint traceShadowRay(vec3 pos, vec3 dir, float dist, uint flags) {
 bool shadowTestAlphaMask(vec3 pos, vec3 dir, float dist) {
 	rayQueryEXT rq;
 	const uint flags =  0
+		// TODO figure out whether to turn off culling for alpha-tested geometry.
+		// Alpha tested geometry usually comes as thick double-sided brushes.
+		// Turning culling on makes shadows disappear from one side, which makes it look rather weird from one side.
+		// Turning culling off makes such geometry cast "double shadow", which looks a bit weird from both sides.
 		//| gl_RayFlagsCullFrontFacingTrianglesEXT
 		//| gl_RayFlagsNoOpaqueEXT
 		| gl_RayFlagsTerminateOnFirstHitEXT
@@ -84,6 +88,7 @@ bool shadowed(vec3 pos, vec3 dir, float dist) {
 #elif defined(RAY_QUERY)
 	{
 		const uint flags =  0
+			// Culling for shadows breaks more things (e.g. de_cbble slightly off the ground boxes) than it probably fixes. Keep it turned off.
 			//| gl_RayFlagsCullFrontFacingTrianglesEXT
 			| gl_RayFlagsOpaqueEXT
 			| gl_RayFlagsTerminateOnFirstHitEXT
@@ -117,7 +122,8 @@ bool shadowedSky(vec3 pos, vec3 dir) {
 
 	rayQueryEXT rq;
 	const uint flags = 0
-		| gl_RayFlagsCullFrontFacingTrianglesEXT
+		// Culling for shadows breaks more things (e.g. de_cbble slightly off the ground boxes) than it probably fixes. Keep it turned off.
+		//| gl_RayFlagsCullFrontFacingTrianglesEXT
 		| gl_RayFlagsOpaqueEXT
 		//| gl_RayFlagsTerminateOnFirstHitEXT
 		//| gl_RayFlagsSkipClosestHitShaderEXT
@@ -133,6 +139,8 @@ bool shadowedSky(vec3 pos, vec3 dir) {
 		const uint geometry_index = rayQueryGetIntersectionGeometryIndexEXT(rq, true);
 		const uint kusok_index = instance_kusochki_offset + geometry_index;
 		const Kusok kusok = getKusok(kusok_index);
+
+		// TODO this flag can be encoded into custom index, so that we'd need no extra indirection
 		if ((kusok.flags & KUSOK_MATERIAL_FLAG_SKYBOX) == 0)
 			return true;
 	}

ref/vk/shaders/ray_primary.comp

@@ -68,7 +68,7 @@ void main() {
 
 	rayQueryEXT rq;
 	const uint flags = 0
-		| gl_RayFlagsCullFrontFacingTrianglesEXT
+		//| gl_RayFlagsCullFrontFacingTrianglesEXT
 		//| gl_RayFlagsOpaqueEXT
 		//| gl_RayFlagsTerminateOnFirstHitEXT
 		//| gl_RayFlagsSkipClosestHitShaderEXT