The illusive 'Grass Clumps'...

[choronr]

Regardless of settings variations, I am unable to render the 'any' grass clumps in the positions represented in the preview window. Any thoughts you would like to share on this subject would be appreciated.

[Buzzzzz]

Hi Ole Bud! Bob I'm sure it has everything to do with what Matt describes in this thread but I haven't figured it out yet?  Maybe it will help you if you can get a handle on it. Then you can explain it to me. 
http://forums.planetside.co.uk/index.php?topic=1249.15

[choronr]

Thanks Jay for the quick response; however, I think this link refers to a different subject:

http://forums.planetside.co.uk/index.php?topic=1249.msg12484#msg12484

[dhavalmistry]

I think he is trying to say that no matter what he does....his grass looks flat...always....

I have the same problem...

[choronr]

Thanks for both responses. I think I'll try a tree population instead and try to make the dull green layer look a bit more textured ...another challenge!

[bigben]

Is it a population problem or a problem with your grass object?  The default is fairly sparse. Here are some settings that might help... might

Grass object:
100,000 blades per clump, width 5-7m
Blade length defaults to 0.1m which should be long enough?

Grass population:
Spacing 5m

...and bring your camera close to the surface to check it out.

[choronr]

The population is not a problem. The preview render shows the rectangles in place where the grass should be. The point of view is high; so, the grass scale must be small or else it will look out of place. I see the grass during the render process; but, it doesn't show up when the render is completed.

[bigben]

Do you have any displaced surfaces which might cover it?  It sounds like it's getting buried.

[Buzzzzz]

Hi Ole Bud! Bob I'm sure it has everything to do with what Matt describes in this thread but I haven't figured it out yet?  Maybe it will help you if you can get a handle on it. Then you can explain it to me. 
http://forums.planetside.co.uk/index.php?topic=1249.15

Thanks Jay for the quick response; however, I think this link refers to a different subject:

http://forums.planetside.co.uk/index.php?topic=1249.msg12484#msg12484

Bob If you read the replies in this Thread http://forums.planetside.co.uk/index.php?topic=1249.15 it states there's a problem with populations not showing up on terrains with displacements. That's what I was trying to point out.

2 quotes from Matt in that Thread:

When to use additional Compute Normal or Compute Terrain nodes

When you perform large scale displacements prior to the Compute Terrain, sometimes you need to limit them according to slope or altitude. If you need them to know about altitude, use a "Tex Coords From XYZ" node because this is very fast to compute. If your displacements need to know about slope, for example if you use a Distribution Shader to affect displacement, use a Compute Normal. However, beware that Compute Normal and Compute Terrain slow down computation of their inputs, and the slow-down is compounded each time they are used. The slowdown only applies to the input shader network, so if they are high in the shader chain the slowdown can be minimised. It multiplies the time needed to compute the input displacement by a factor of approximately 3.

Apologies for the mini thesis, but I hope it sheds some light. If someone who is not so close to the implementation can offer a summary of the important information, that would be appreciated.


Unfortunately it will re-evaluate this for every populator you have it connected to. However, unless you have multiple objects in exactly the same locations, this would be necessary anyway, so in most typical situations it wouldn't be possible to optimise this without sacrificing accuracy.

EDIT: This is probably a good place to say that you don't have to use the Compute Terrain node as the input terrain for your populations. Any shader network can be used, and it's often better to use the very last shader that plugs into the planet. Misunderstanding this is probably one of the more common causes of populations not sitting correctly on the surface. However, whichever shader you use, you should make sure that the surface normal has been computed either by that shader or further up the chain, otherwise slope constraints won't work on your populations.

Matt

[reck]

Choronr is this what you mean? Not sure if it's a problem with the grass clumps or the sit on terrain feature in general.

http://forums.planetside.co.uk/index.php?topic=1335.0

[Buzzzzz]

I think he is trying to say that no matter what he does....his grass looks flat...always....

I have the same problem...

I am aware of his problem and I'm trying to direct him to a post that has to do with this problem, if people would just read it.

[helentr]

There is another issue with the grass clumps, that you may not be aware of. It is a large flat object and only shows on (almost) completely level ground. Any slight slope and the grass is buried on one side and flying in the air on the other.
At first I thought that the population consisted, if not of single grass blades, at least of small groups, but that is not so.
Look at this image. You can see the flying grass, but the buried half is invisible.

Helen

[fmtoffolo]

yeah, the pop doesn't adapt to the terrain. a work around is to use smaller patches of grass,,but the instances go to roof...and the memory usage,,,just too much

[sonshine777]

yeah, the pop doesn't adapt to the terrain. a work around is to use smaller patches of grass,,but the instances go to roof...and the memory usage,,,just too much

This is what I do if I use the stock grass clump you can remedy that by only making the population cover what the camera will see. Sometimes you would be amazed at how small you can make the edges of the population and still get coverage in the camera view.

I use a grass model that I built that is rounded down at the edges and thus makes it sit on hillsides better.
Here is the link on the Terranuts site for the download.  http://www.terranuts.com/forums/downloads.php?do=file&id=505
This grass clump does look more like field grass and is not as even as the stock grass that comes with TGTP, but usually I am looking for "field" grass not "lawn" grass.

[Harvey Birdman]

That clump of yours looks pretty good, guy. Thanks.