Dynamic Lights

[Patrick87]

I have been reading up on the lighting systems in the UDK trying to figure out the best way to light up my level. What I want to know is, is there any reason for me to use a Dynamic Light if there is nothing that is moving in my level out side of the player and the gun.

If I do use dynamic lights I want to use a light environment to cut down on the processing power that is going on while the level is being played right?


Thanks

- Patrick

[Crusha K. Rool]

Dynamic light means that the light can move or be toggled on or off.
"Static" lights are all set to lit dynamic objects by default, so there is nothing you can do wrong.

[taz1004]

Just so you know, there seems to be difference between dynamic "light" and dynamic "shadow" in UDK. Something like the following is where you would use dynamic "shadow"
http://www.youtube.com/watch?v=EglwOqvt4Io

But it isn't necessarily using dynamic lighting and it can be achieved very cheap. It is actually using static light environment with dynamic shadow. And runs at about same frame rate as full static light environment. Fully dynamic lighting and dynamic shadow on this same scene however, dropped the frame rate to 15fps instead of smooth 60fps as you see in that video.

Again, if there's nothing moving in your scene, there's no reason to use either dynamic light or shadow but just wanted to point this out for future reference.

[ambershee]

Dynamic light means that the light can move or be toggled on or off.
"Static" lights are all set to lit dynamic objects by default, so there is nothing you can do wrong.

This is completely wrong. Dynamic lights and static lights are different; static lights will be used in order to generate lightmaps, which in turn will result in the ability to use more complex lighting features such as global illumination (and have much smoother lighting overall). Dynamic lights will light everything dynamically when the game is running on a per-pixel basis, which is considerably more expensive in terms of shader processing time.

Both static lights and dynamic lights can light dynamic objects such as animated skeletal meshes or interpactors - which will be lit dynamically regardless (you can't bake lightmaps into something that changes, obviously). Both static and dynamic lights are also able to cast dynamic shadows (static light lightmaps may also include 'shadow', although this is more of an absence of light on the lightmaps themselves, which is different to how dynamic shadows work).

Finally, lights that are toggled on and off can be either dynamic or static, and it's often better for them to be static. The game just uses two sets of lightmaps, one for when the light is on, and one for when the light is off.

[Patrick87]

Okay so new question here, I have turned off shadow casting for all of my lights because I don't need it on, Static and Dynamic, however my light changes to a dynamic light when ever I turn off cast shadows. Should I be concerned about this, is it easier to keep the static lights' cast shadow propertie on and just set the meshs to not cast shadows?

[Crusha K. Rool]

Finally, lights that are toggled on and off can be either dynamic or static, and it's often better for them to be static. The game just uses two sets of lightmaps, one for when the light is on, and one for when the light is off.

Well, except for this last sentence was that exactly what I said.


Also I thought that UE3 still uses Vertex Lighting in conjunction with the lightmaps (I remember that I read something like that in Hourences' tutorials somewhere), but maybe it just changed over time…

[ambershee]

Well, except for this last sentence was that exactly what I said.

No, it isn't. A dynamic light can for example be stationary and not toggle. A static light can be toggled. Whether a light is dynamic or static is not dependant on it's ability to be moved or toggled (although static lights cannot be moved since the lightmap system doesn't work with this).

Also I thought that UE3 still uses Vertex Lighting in conjunction with the lightmaps

I don't believe this is (or was) the case. Perhaps in UT2004 and UE2 vertex lighting would have been more prevalent, but vertex lighting isn't very common any more save in perhaps games that don't strictly benefit from more accurate lighting simulations (such as an RTS). Vertex lighting is a shader technique that stems from dynamic lighting.