Dither opacity noise on animated mesh?

melviso

Using dither opacity works wonders for translucent objects but when animation is added, there is this noise that appears that tend to lag behind the mesh as it moves.
Also is there a way to place a dynamic light to only cast shadows but not light the object using lighting channels?

Obscura

You could adjust the temporal aa setting to reduce the ghosting (lag in your description). Search for temporal aa ghost to find the right console command. From what I remember, its the "current frame weight" but I'm not totally sure.

As for the second question, I'm very cerain you can't.

melviso

Thanks, what of negative light in ue4?
https://answers.unrealengine.com/questions/10390/requestnegative-lights.html

Obscura

Never tried. There is an example image in the post you linked so you could copy it and try it out.

melviso

Just found out about distance field indirect shadows. No need for the negative lighting.
EDIT: Distance field shadows doesn't work with simple grass wind plugged into world position offset?

Obscura

Distance field shadows doesn't work with moving things, because the distance field representation is static, and pre calculated. What are you trying to achieve?

melviso

I have some inhouse plants that move softly with the wind using simple grass wind. Since they are indoors, they are not directly lit by the sun, so they would need indirect shadows for the movable mesh, hence the consideration of a negative light to get the indirect shadows.
I thought distance field indirect shadows would work.

I don't know why we can turn off lights shadows, why can't we turn off lighting and let the shadows remain to simulate indirect shadows? That would be an easier way. Lighting is such a complex phenomenom that most times, u have to break some rules to get the direct results easily and I think there is yet to be a true renderer that graps the true workings of light imho.

Obscura

Its a game engine

But there are several workarounds, none of them are easy though.
1. Custom shadows using blueprints. This requires some blueprints knowledge, but it can be used to make fake shodows too:
http://shaderbits.com/blog/custom-per-object-shadowmaps-using-blueprints

2. Capsule indirect shadows on a skeletal mesh. The downside of this is that you would need  to convert your mesh to skeletal and have a skeletal animation.

3. This would require some pre processing, and agian, some blueprints knowledge. You could put a real light there, make the object hidden but cast shadows. Render the animated shadows into several textures, and later just play it back by swapping the textures in a dynamic material instance. I think I would go with this because its fairly easy to control and set up.

melviso

Obscura said:

Its a game engine

I know lol. It's just a little cumbersome, when u think of an idea but it's not that simple to implement. If this was possible, it woud save a lot of lighting artists time and effort though  

I thought of the capsule indirect shadows but that would be too cumbersome, since u are trying to get a reasonable amount of leaves movements for the shadows.
Thanks for the workaround, mate. These look dope. 
Option 1 looks very interesting. Does this handle cast shadows on other objects or self shadowing? I think I have to start learning blueprints on a serious note. I hear it is very powerful.
Isn't that the blog of Ryan Brucks. I remember watching this:
https://www.youtube.com/watch?v=QGIKrD7uHu8
I absolutely have no idea what he says in this video. It's like another language  

About option 3. Can u chose the uv sets to bake the shadows to. Also, does this involve the use of the flipbook animation blueprint. But I am wondering if  simple grass wind movement is random but I don't think the animated shadows baked to textures need to be accurate. 

If its not too much trouble, can u give an outline of how I can go about doing this? 

Obscura

You don't need any uv for option 3. Shadow is like a projector. Pretty much like a decal. Its the object shown from the light's perspective. To simulate omni/point light, you would use a cubemap depthmap of the object, captured from the light location. For directional light, its simpler. Imagine  like you place a camera on the light, turn it towards the object, and you look through it. Option 1 does the exact same thing. You wouldn't need flipbook either, you would switch the texture every frame. So for a 100 frames animation, you would use 100 shadowmap textures.

melviso

With option 3, can shadows be blurred to fake soft shadows?

Obscura

Sure, thats why it takes an offline approach by baking textures, so you can apply expensive filters, like a high quality, wide kernel blur without affecting performance.

melviso

Ok. Thanks mate.