Hi trytoh,
I’ll break down your questions into sections and respond accordingly since there is a lot of information here.
I also see that you’ve marked that you’re using 4.11 P1, which has some known and not known issues right now. Preview builds are best for being used for testing our new features, but not actively developing in. 4.11 is going to introduce a lot of new Rendering features, but there are some pretty hefty known issues right now with some features like skylights and exponential height fog.
Q1/Image 1: Light Bleed
As you’ve pointed out you’ll want to adjust some of the settings in the dynamic light, although if you’re using a Directional Light like your image shows, I wouldn’t adjust the shadow bias or filter sharpen before first adjusting the options under the Cascaded Shadow Maps category.
You can refine the lights quality and shadow casting by adjusting these values first. Then maybe slightly tweaking the shadow bias. Point/Spot Lights will not have these options though. Only shadow bias and filter sharpen.
This page I wrote on the Lighting Troubleshooting and Tips Guide on the Wiki should help you with this to some degree.
Q2/Image 2: Distance Field RayTraced Shadows
Unfortunately, that image doesn’t really help identify the main shadowing issue with the scene. You will want to use the Viewmode > Show > Visualize > Mesh Distance Fields to see what your mesh distance field representation looks like in the scene. There are a few things that can affect the mesh distance field. These can include the size of the mesh and the distance field resolution needs to be raised in the build settings. Distance fields work best with modular pieces rather than larger geometric pieces, if that is the case just break the mesh up into smaller pieces and rebuild the scene.
This page here can help you identify quality and troubleshooting these types of issues. Even though this is on the Distance Field Ambient Occlusion page, the method applies to Distance Field usage in general.
Q3/Image 3: Stationary Light BP
If the root of the BP is set to movable the light will be forced to be movable, but if for instance you have a BP and there is a root component and two other components, like a light and a static mesh. You can set the Light to be Stationary and the mesh to be static or movable without issue, but if the BP as a whole is movable based on the roots mobility it will determine what the other components should be set to.
So by your question if you set the BP to movable, the light will now be movable as well. If you want to use Stationary Lights these can cast shadows that are baked/precomputed and the quality will depend on the lightmap resolution of the mesh where the shadow is being cast.
Q4/Image 4: Direct Shadowing/Sky light shadow color
I cannot answer the question specifically about direct shadowing and opacity. I’m sure there is some limitation here that I’m not really aware of and I’m not a rendering programmer, or even a programmer. The skylight can produce the soft ambient occlusion, but only for static and stationary. If you want it dynamically it would be best to set the Skylight to movable and if you have Generate Mesh Distance Fields enabled for your project this will use dynamic AO. You can use the viewmode Show > Visualize > Distance Field Ambient Occlusion to see it’s representation in your scene. You can also adjust the light color and Intensity to get the shadow color that you would like. The distance field ao page linked above covers this information as well along with quality and troubleshooting to get the best results.
Q5/Image 5: Unreal Lighting
Lighting can be an art in itself to get right and understanding all the things that can affect or go into setting something up takes a while to get a grasp on.
I hope this helps.
Tim