Grass instancing

Ati

Hi,

I've noticed that Bryce can instance trees really well. When I try instancing grass props from Daz Studio, it becomes a bit more unpredictable (crashes a lot more often). A full scene needs more grass than trees, so it may just be the big number of instances I try to force on it.

I found this product: http://www.daz3d.com/bryce-instance-grass

Do you know if this is better than using grass props from other products, such as http://www.daz3d.com/nature-forest-flowers (which is what I'm using now) ?

Thanks,

Ati

Chohole

Yes, because it is meant for Bryce, and the instancing lab.  The other set tends to be much higher poly, so doesn't play nicely. I often crash Bryce scenes if I use too many of that PAs props.

sriesch

One thing that may help, if you pick a product that has image texture maps on it, you could simply remove the image and just set the diffuse color to plain green or yellow or whatever or use a Bryce material on it.  That should reduce the memory footprint a bunch, and as long as you aren't doing a closeup of the grass, the loss of detail from a texture map to a solid color might not even be visible.  If you are sending from DAZ Studio to Bryce, ideally of course you will want to eliminate the images before sending not after.

For products you already own, you can also do a few quick tests in an empty scene to get the count of polygons for each of the grass objects you might want to use, it might be quickly obvious that one has a dramatically higher polygon count than the other.  Be advised that are are some very low-resolution grasses which, while great for not running out of memory, might prove to be to angular to use for some renders.

Horo

Additionally be aware that grouped objects don't instance, they are just copied. If an object is truly instanced, the wireframe lines are interrupted. There are two great tutorials about instancing: Bryce Instancing Without the Instancing Lab by Fencepost (https://horo.ch/docs/guests/pdf/InstancingWithoutLab.pdf) and How to use the Instancing Lab in Bryce 7.1 Pro by Rashad Carter (https://horo.ch/docs/guests/pdf/InstancingLab_Rashad.pdf).

 

Chohole

Ah.   I just checked, and the Esha grass pack that Ati is talking about is the one that is made from planes, with a mat and trans.  I am not at all sure how you use those in the instancing lab, as each grass "prop" is a group of planes.  I mostly use her other grass, which is geometry grass  http://www.daz3d.com/grassy-grounds-megapack

Dave Savage

You can also get very good results using the grass objects in the Bryce library, but bear in mind what Horo says about grouped objects.

Several of the best Bryce native grasses are groups of 2 or three mesh objects, so you ungroup them before entering the instance lab. This also has the added advantage of each individual object being able to be rotated (which again groupd objects won't do in the Instancing Lab).

You can set upto 5000 instances in one go, but then when you leave the IL, it's advisable to select the group it creates (called: unkown), ungourp that and immediately regroup it and give it a name), then in [A]Attributes, set the goupr to show only as  box (this reduces the amount of geometry the screen has to draw) and then go back to the IL to do another layer... You can usually do this upto 3 times before Bryce crashes thereby achieving 15000 clumps of grass.

 

Hope this helps.

Ati

Thank you for all the feedback!

sriesch said:

One thing that may help, if you pick a product that has image texture maps on it, you could simply remove the image and just set the diffuse color to plain green

This was a great trick. I stripped off the diffuse and opacity images, and it works like a charm! :)

Horo said:

Additionally be aware that grouped objects don't instance, they are just copied. If an object is truly instanced, the wireframe lines are interrupted. There are two great tutorials about instancing: Bryce Instancing Without the Instancing Lab by Fencepost (https://horo.ch/docs/guests/pdf/InstancingWithoutLab.pdf) and How to use the Instancing Lab in Bryce 7.1 Pro by Rashad Carter (https://horo.ch/docs/guests/pdf/InstancingLab_Rashad.pdf).

Good tutorials, thank you! I've been watching youtube tutorials for the past few days, very informative.
 

Chohole said:

Ah.   I just checked, and the Esha grass pack that Ati is talking about is the one that is made from planes, with a mat and trans. 

It is? Oh. Good to know. So it's similar to what I'm using now. With the images stripped off the object, it works really well. I think I'll use what I have for DS for now.

Dave Savage said:

You can set upto 5000 instances in one go, but then when you leave the IL, it's advisable to select the group it creates (called: unkown), ungourp that and immediately regroup it and give it a name), then in [A]Attributes, set the goupr to show only as  box (this reduces the amount of geometry the screen has to draw) and then go back to the IL to do another layer... You can usually do this upto 3 times before Bryce crashes thereby achieving 15000 clumps of grass.

With this 5000 and 15000 numbers in mind, I think I'm quite happy with the results. On my test image I managed to place 50.000+ clumps of grass, without a single crash, and memory usage is still only 440M.

I'll see how it turns out in an actual scene, but so farit's looking really good!