Mesh clutter / Grass obj generated by landscape tool

[qwert_e]

Hello. Following documentation


I created MeshClutter with trees,  set Size X , Size Y = 700, Step = 35. Then i created impostor (ObjectGrass) for it with the same parameters (except Subdivision = 32 and Step = 1120).

But when landscape tool had generated terrain, i got MeshClutters with Size X , Size Y = 3627.4550, other is the same.
I assume this could happen because resolution of created masks is 4096x4096 and scale factor is 0.889 m/pix
What am i supposed to do to match Size and Step?

[morbid]

Hello qwert_e,

Landscape changes grass and/or clutter object size respectively to the mask resolution. Step value in this case should be modified manually, according to the object size. 

For instance, low step values (10-50) works well with small, but high detail areas. Bigger values (100-700 and more in some cases) should be used with huge objects. Keep in mind that each grass/clutter cell requires one draw call. If you have 4000 x 4000 units objects with step = 75 you'll get a decent amount of draw calls per object, which will decrease performance.

I suggest the following:

1. With Landscape Tool always use bigger step values starting from 500
2. With local "hand made" areas use lower step for better performance

If you already generated terrain with trees just multiselect all your objects and change step value.

Thank you.

[qwert_e]

So what with the constraint "Size/Step"?

[morbid]

Before 2.8 size should be divided by step without remainder. However, this wasn't obligatory and we suggested this approach only if some mask related artifacts were visible.

In 2.8 we've improved grass and clutter behavior and there's no need in some specific step size. The main rule I described above.

[qwert_e]

Okay. One more thing about grass - i`ve experienced some "saw" behavior on grass enable. 

Examining profiler, i figured out that it is WorldIntersection calling, But the grass even isn`t rendering

Some sample parameters:

[qwert_e]

Also impostors are set on runtime... and it takes minutes when all impostors are in their place

[morbid]

Which SDK version you're working with?

Density = 5 is a very high value for big terrain. Consider lowering density, more likely this is the main reason for slow grass cells generation and performance hiccups.

For comparison, in our terrain add-ons the density for trees is equal to 0.002

Thanks.

[qwert_e]

SDK ver. 2.9.0.2 

That density was for grass (5 or even 20)
without (5 or 20) close-up view is very poor, but in flight it must not be rendered and computed

please compare and give some tips

[morbid]

Do you need grass scattered over all terrain?

Which visibility distance for grass is used? I'd suggest for this case bigger step and lower visibility distance, for example, step ~ 200 and visibility range around 50 units.

The best rest result I suggest making terrain detail color indistinguishable from grass color. This will help you to make visually seamless transition from the object to the terrain surface.

You can modify both detail and grass material to do this.

There's another technique that might be helpful: think of grass objects as of LODs, for instance:

1. Low-detailed grass with highest step value and low density, let's say step = 800 and density = 1 or even less. You can increase visibility distance for this object, the cells will be generated quite fast.
2. Mid-detailed grass. Reduce step, increase density and lower visibility distance
3. And so on

I think two or three groups could be enough. Keep in mind that increasing number of objects in the scene will affect CPU load. In a perfect situation detailed grass should be created only in a limited areas of interest, where your helicopter will land or hover.

If you still struggling with settings (they could be really complicated) — send us a test scene and describe desired results. We'll check what can be done with vegetation objects.

Thank you.

[qwert_e]

Hello!
I set subdivision to 1 (according to docs) on grass - 8 was a mistake. Intersections became much faster, and no "saw" in profiler!
next question is about shadows... shadows on trees makes huge fps drop in close distance. And i have some issue tuning normal shadow behavior to make it beautiful at close dist and in large - it starts to disappear at 800-1200 from camera