NewLight Point/Bugs and limitations
Deferred lighting have issues with transparency
Deferred lighting is incompatible with transparency. In some cases, it shows one of the lighting layers applied to the color of the transparent texture.
This bug is currently available by default for VertexLitGeneric and Lightmapped_4WayBlend, if they are using $translucent material parameter.
No $translucent. Behind the wall placed lighting and some models with small room.
With $translucent. Now player see everything, but only what lighted.
An example with model.
The same happen if used $decal material parameter.
An example.
This problem also applies to brushes which don't use $translucent, but which is a part of a func entity with a transparency brush (the only exception is func_detail). This happen even if transparency used for shader that doesn't shows one of the lighting layers.
This sticker is brush, that is part of func_brush, which uses glass as part of itself. Flashlight off.
This sticker is brush, that is part of func_brush, which uses glass as part of itself. Flashlight on.
If a func entity or model uses render mode Glow (3) or World Space Glow (9) - they will show one of the lighting layers. This means that you can't use this renders to make your brush transparent, you will have to create a separate texture.
Clear example. The box with fire extinguisher and brush uses the render modes.
Other render modes will have similar effect, but only for brushes.
Clear example.
Similar issue happen with overlays/decals on brushes with $translucent.
Metal speaker is overlay that use $alphatest, but lighting of the health charger visible anyway, because overlay pasted on the transparency window.
In some cases, use $alphatest, if it'll give similar to $translucent resualts, with this your surface also will cast dynamic shadows.
Confirm:Is there more shaders with this issue ? Confirm:Is there more ways to get this bug ?Deferred lighting doesn't shows on transparency materials
Very noticeable with shaders that doesn't shows one of the lighting layers applied to the color of the transparent texture. Properly works with $alphatest.
An example. Expected that you will see shadows from the ropes and the plastic road cone on the window.
The same moment, but in
Portal 2: Community Edition (this game uses env_cascade_light from 
Counter-Strike: Global Offensive.)
Flicker near light volume edges
Often meeting strange clipping/flickering, strange bug that was in early stages of the game (this can be seen even in videos before new lights release in public). Somehow related to Range value, since changing its value halfway fixes this bug, because it move away the bugged area. With Necro Patch, this is fixed for newLight_Spot.
One of many examples.
One of many examples.
Brush polygons may clip deferred lighting
Rare phenomenon, sometimes brush polygons clip deferred lighting, the reason that cause this is unknown. Can be easy fixed if divide invalid brush into two parts.
Note:Most often happen if map used fast compile settings.
One of examples (mat_wireframe 0).
One of examples (mat_wireframe 1).
One of examples (mat_wireframe 0).
One of examples (mat_wireframe 1).
Deferred lighting shines through nodraw texture
Not a bug, but a pattern. Unfortunately, this cannot be controlled in any way, you should keep in mind this before paint nodraw to escape situations like in the gifs.
Workaround:If your dynamic light source illuminates face that player never see - use cheap textures with low resolution and which don't use material shader parameters, a good solution would be tools/toolsblack or any UnlitGeneric texture.
Black Mesa - bm_c2a2a.
Black Mesa: Blue Shift - bs_c0m0c.
Objects with refract shader self refract if illuminated by deferred render
Objects with refract shader in their own refraction disable self, to escape some problems. However - objects with refract shader illuminated by deferred render refract self because of game can't tell the depth of objects because of the transparency, what you are see in the pictures is just the lighting layer applied to the color of transparency texture.
as_c3map01 - flashlight disabled, everything looks fine.
as_c3map01 - flashlight enabled, now this magnifying lamp refract self.
Similar issue happen if model with refraction behind wall with refraction.
Flashlight disabled, everything looks fine.
Flashlight enabled, now this wall show one of magnifying lamp deferred lighting layers.
Workaround:Divide model into two separate parts, one should use only textures with refraction, the second without textures with refractions.Viewmodel illuminated by deferred render draw in refract shader
Refract shader and Water shader take and refract player screen space without taking into account viewmodel. However - viewmodel illuminated by deferred render draw in refract shader because of game can't tell the depth of viewmodel because of the transparency, what you are see in the pictures is just the lighting layer applied to the color of transparency texture.
Clear example in test map, the hivehand illuminated by deferred render draw in the refract texture, plus it's completely discolored there..
Black Mesa - bm_c4a1a.
Black Mesa: Blue Shift - bs_c2m0a.
Motion Blur blurring viewmodel lighting layer
For some reason Motion Blur blurring viewmodel lighting layer, you can notice this when you just rotate camera.
An example.
Strange "holes" when player's camera is at a great distance
In some cases may will appear strange "holes" when player's camera is at a great distance. Strange bug that occurs quite rarely. It is affected by game resolution, for example in bm_c4a1b1 this bug shows up well with a resolution wtih 1920x1080, but with 3840x2160 the light source from the teleporter flickers, but does not form a hole.
Confirm:Does it happen with newLight_Spot ?Workaround:Can be fixed with NormalBias value increasing.
Example in bm_c4a1b1, the green teleporter light source starts to glitch when player move certain distance (crossbow zoom doesn't effect to this bug, unlike HEV zoom).
Black Mesa, map bm_c4a1b1. NormalBias - 1.
Black Mesa, map bm_c4a1b1. NormalBias - 5.
Black Mesa: Black Ops - Restored, bmops_map_2. NormalBias - 0.5.
Black Mesa: Black Ops - Restored, bmops_map_2. NormalBias - 1.5.
Gbuffer doesn't draw while cubemaps is building
Deferred lighting, godrays, xog and other gbuffer effects doesn't draw while cubemaps is building. This means that you will not see any lighting from new lights in cubemaps.
This is what see player.
This is what shows cubemap reflection (note the reflection on the RPG doesn't shows any lighting from this crystal).
This is how it looks while cubemaps is building.
New lights doesn't work with 3D Skybox
Don't use new lights in your 3D skyboxes, none of them will work at all.
An example. We see that deferred lighting and Godrays works fine, but 3D Skybox doesn't draw both.
Materials reload cause new lights disappear
Only for new lights which uses shadows. This issue happen when you open Hammer while game is opened, when you disable speculars with mat_specular 0, when you reload all matelias with mat_reloadallmaterials, e. t. c. Can be fixed with save reload.
Before
mat_reloadallmaterials.
After
mat_reloadallmaterials.
Gbuffer incorrect work with cloak
Cloak is a material shader parameter for VertexLitGeneric shader, female assassins uses it to make self transparent when they need it. Godrays all time fully render through them, same for deferred lighting and xog, even
bm_c2a3c, the sun's rays are not cut off despite the fact that she is completely untransparent right now.
bm_c2a3c, she is completely untransparent, but we still can see one of lighting layers.
Deferred lighting incorrect work with Customize Character window
For some reason Customize Character take player's screen, inserts it into character preview window and show one of deferred lighting layers.
An example with zombie scientist model.
Deferred lighting does not draw with -tools
If you don't use Full Screen - deferred lighting will not draw.
In
Full Screen.
Out
Full Screen.
Broken water transition in viewmodel
You can note the broken lighting transition when you go into water (only if water is world geometry and uses refractions).
An example.
Godrays incorrect work with $translucent
Godrays (also disk) all time fully rendering through textures with material shader parameter $translucent, because of this you will see unexpected results like in the picture (the same issue happen if used material shader parameter $decal). Disable godrays when you need or use $alphatest if it'll give resualts similar to $translucent. You also can try use some other tricks to escape this problem.
Bug example in bm_c1a3c.
Sign from other side.
Godrays fully draws through water
Deferred lighting doesn't fully draws through water, unlike godrays.
Black Mesa: Blue Shift - bs_c3m0c.
Godrays leaks
Due to way how godrays works, in some cases you can note the leaking. Can be drawn even through walls, appearing where they should not be visible at all. Disable rays with triggers or minimize effect.
An example.
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Godrays doesn't process viewmodel if player is underwater
Necro Patch fixed the old issue with godrays that wasn't processing models above water. This fix caused new issue, now godrays doesn't process viewmodel if player is underwater. Doesn't happen with func_water and func_water_analog.
Player is not underwater.
Player is underwater.
Godrays can't be displayed in monitors and reflections
Godrays is post process effect that depends on player screen. That means that they can't water reflections or monitors can't show it.
Note:Godrays for monitors and reflections was added with Necro Patch. However, this is disabled in the code by default, because it didn't work correctly. There is no way to enable this feature.
An example.
An example.
Godrays doesn't refracting by refract shader and fully draws through
Unlike deferred lighting, godrays doesn't refracting by refract shader, also fully draws through.
An example.
Moving lights with shadows are buggy
In some cases, your attached lights may have buggy shadows if parent is moving.
An example.
bm_c1a1c.
Can be partially fixed with NormalBias value increasing. Also, if your moving light is just simple decoration (the puzzle crystals from Xen is great example) - highly recommended to leave shadows disabled to save limits and performance.
NormalBias- 1
NormalBias- 10
Shadows incorrect work with newLight_Point cube edges
Because newLight_Point is cube technically - we get shadows incorrect behavior with edges of this cube, this cause their serious distortion a.k.a. clipping. You only can minimize this if set shadow quality to maximum.
One of many examples.
One of many examples.
One of many examples.
Shadows have noise
This noise appeared with Necro Patch, greatly spoils blurry shadows. The only workaround is to make ShadowRadius value very low, but then the shadows will become extremely sharp and stepped.
An example.
Shadows doesn't appear immediately after reload
After game save and load shadows don't appear for short time, maybe it has something to do with caching. This appearance duration may vary depending on power of user PC and how much of lights with enabled shadows are turned on at level, but in any case user will get this issue even with most powerful PC.
Workaround:Enable in worldspawn settings Level Fade In to hide this problem, this setting also will hide some other issues with loads that avaible in 
Black Mesa.
With no
Level Fade In. It seems like the shadows flicker, which makes it unpleasant for eyes.
With
Level Fade In. Everything looks fine.
Shadows don't appear immediately with a lot of lights with shadows
If your level use a lot of lights with shadows - shadows from enabling lights will not appear immediately, this happens if light source was disabled and if player's camera did not see this light source enabled initially.
Workaround:Before turning on light, set the intensity for light (via SetIntensityForLight input) to 0, then turn on light source and set the intensity to the desired value with delay of 0.5 seconds. Also, nr_shadow_max_passes_per_frame set to 25 can help in some cases.
An example.
bm_c2a1a.
Shadows low passes per frame if used a lot of lights with shadows
Sometimes many lights with shadows sets low values for nr_shadow_max_passes_per_frame cvar. This cause shadows to be looking a lot less natural.
Workaround:Very easy to fix with point_servercommand, just place logic_timer which will fire nr_shadow_max_passes_per_frame 28 command each 2 seconds.
nr_shadow_max_passes_per_frame - 16
nr_shadow_max_passes_per_frame - 28
Viewmodel doesn't support self-shadowing with deferred ligths
Unlike cascade shadows - viewmodel doesn't support self-shadowing with deferred ligths. Not a bug, but this is not what you expect from real life, it also isn't so with env_projectedtexture.
Here you can see how one of gluon gun switches create shadow that fall on other part of gun.
Light spot illuminates gluon gun, but lighting just ignore viewmodel and fully shine through, although only the side of the gun should be light.
Weapons dynamic light incorrect work with damaged func_breakable_surf
For some reason weapons dynamic light can illuminate damaged func_breakable_surf even if position of it very far from position of damaged func_breakable_surf.
Confirm:Is there a way to fix this?
An example.
