rain

[dreamhead]

hi

i was wondering how to get a good rain effect white leadwerks, i use particels but they dont give a good effect wat i need.

so any ideas?

[TylerH]

If you take a look at the Jeklynn Heights C++ code, there is a weather system with code for rain that produces a pretty convincing effect.

[Canardia]

I'm using physics rain, it doesn't look as good as graphical rain, but it works better. For example the rain drops don't fall inside buildings, and you can look out of a window and see rain outside, and no rain inside. What also works better is that the rain drops can cast shadows like real rain does, and the rain drops can be lit by lights, which makes it look good in the night also.

 

Around 1000 cubes doesn't slow down the FPS too much, but it depends how low your FPS originally was. With 100 cubes you still get decent rain, but not so heavy of course.

 

Of course the center of the rain area always follows the camera, so you don't need so much rain drops.

Maybe if it was possible to write a smear shader, then the rain drops would pull tails behind them.

[TylerH]

Sounds interesting, have a demo?

[Rick]

Would 1 sided planes that always face the player (only along the Y axis though) be more efficient than cubes? The planes could have a transparent image of a rain drop type.

[Canardia]

Would 1 sided planes that always face the player (only along the Y axis though) be more efficient than cubes? The planes could have a transparent image of a rain drop type.

It might be, I have to try different methods and see which takes the least FPS. Also the cube physics shape might not be the fastest, although I heard that the primitive shapes on Newton are much faster than any custom composed shapes. I could still try if a tetrahedron physics shape would be faster than a physics cube.

[dreamhead]

I'm using physics rain, it doesn't look as good as graphical rain, but it works better. For example the rain drops don't fall inside buildings, and you can look out of a window and see rain outside, and no rain inside. What also works better is that the rain drops can cast shadows like real rain does, and the rain drops can be lit by lights, which makes it look good in the night also.

 

Around 1000 cubes doesn't slow down the FPS too much, but it depends how low your FPS originally was. With 100 cubes you still get decent rain, but not so heavy of course.

 

Of course the center of the rain area always follows the camera, so you don't need so much rain drops.

Maybe if it was possible to write a smear shader, then the rain drops would pull tails behind them.

sound very interesting,do you have any vid of demo of or tut,to see how to use it

[Canardia]

I can make a demo soon, but first I need to optimize it a bit more. It's still too slow when used in a real game, even when it seemed not to take too much FPS in the tech demo

[Pixel Perfect]

Sounds like a nice solution if you can avoid the hit on the fps ... look forward to a demo.

[dreamhead]

I can make a demo soon, but first I need to optimize it a bit more. It's still too slow when used in a real game, even when it seemed not to take too much FPS in the tech demo

yea i can't wait to see a demo to

[AggrorJorn]

I imagine that objects that no longer move get deleted? The solution seems cool and has many benefits as the rain exists out of enities (as you mentioned). If you can make the fps stay relatively okay, then this could work in this case. Since we need it to work in a situation with a fixed camera position, there should be plenty of pc performace left for the rain.

 

On one hand it would still be neat to have direct influance over particle angle direction. This has happened to me before with smal flames and also rain.

[Canardia]

Yes, objects which stopped moving are deleted, and also objects which fall under the ground (you can adjust the Y value).

 

Today I came up with an idea which could improve the performance a lot:

Not using physics, but doing a raycast matrix over the whole terrain and all objects on it with a given grid resolution.

When raindrops fall below the matrix, they will be deleted. The below check has to take also the speed of the rain particle into consideration, so that it will be deleted if the next iteration would bring it below the matrix.

That will do the same as physics, so raindrops don't get inside buildings.

 

If raycasts are fast enough, then it might also work fully dynamic without a precalculated raycast heightmap.

[Rick]

From my experience raycasts are far from fast, so I'm thinking the precalc is going to be required. I have to wonder how fast it would even be to make this heightmap for raycasting. Are you thinking of casting a ray for every possible point and store off the height at which that ray hit something? I would think that would take a long time to compile such a heightmap.

[Canardia]

No, like I said, there would be a grid resolution, so basically like a heightmap resolution, which you can adjust when creating the rain class. Moving objects could also update the heightmap with a given frequency, so it would not be static.

[Rick]

So I assume that means the accuracy of rain and it's colliding with things would depend on the resolution one picks?

[Canardia]

Yeah, although it could be quite high, maybe 8192x8192 (=256MB), since you can prefender it and save/load from disk.

[Rick]

256 MB?? I don't even want to think about how long it would take to run that many raycasts to make that much data!!

[Canardia]

You need 67 million raycasts

Well, but it doesn't really matter since you can do the precasting outside of the game, so the game only loads the heightmap.

[Rick]

And a ton of free time to let that process

 

It'll be interesting to see in practice.

[AggrorJorn]

but 8192 x 8192 is quite a large area. If you would concentrate this only around the arae of the player then this wouldn't cost that much calculation time.

 

I also what kind of method Tyler used for his C++ code. Having a loot at that later this evening.

[Canardia]

But the player is moving, so the area around the player would need to be recalculated each time he moves. The 8192x8192 is precalculated and not raycasted during game play.

[Sean]

Torque uses raycasts for rain. Hardy any FPS hit unless it is really pouring. I think they use a "thick" ray to find objects etc. but each drop also has splash animation when each drop hits something. Not sure how that works but i will look into it.

[Rick]

I just remember using real-time raycasts for terrain decals (was probably doing something like 20+) and the fps was a very noticeable drop.

 

Doing ran in a shader would be the best way to do it, but making shaders is a pain and it seems not many people can do it.

[AggrorJorn]

Fact remains that changing the draw angle of a particle would be sufficient. It says so in the documtation that particles can be used for creating rain. But without changing the particles shader, it is not possible.

[Canardia]

How do you prevent that the rain goes through objects with particles and shaders?