uploading geometry and performance

[tricky]

This is not really a problem with VRay - more with the limitations of our aging hardware. Our workstations have 8GB ram whilst our farm machines (whilst having faster processors) only have 4GB. We are looking to upgrade these, but in the meantime, could anybody give me any pointers?

We have a relatively modest scheme with a couple of large hotel-type buildings and a number of ForestPro objects. Some of the ForestPro objects contain high detailed grass, flowers and trees. We used to paint in grass/flowers/trees etc, and in some cases, we still do. however, ForestPro enables us to use 'real' 3d objects that can save time, particulary for multiple views of the same scene.

The problem is the 'unloading geometry' portion of rendering which I assume is because there is just too much data that VRay is having to load into memory in order to render.

I am using IMap/BF rather than IMap/LC as I assumed this meant the geometry was loaded in only when the bucket 'sees' it, whereas LC would have to load the entire scene into memory at once to calculate the GI (I could be massively wrong with this!).

I have set the dynamic memory limit to 2500MB, though to be honest, I don't really know what this should be set to.

GI has calculated fine, and it is during the actual rendering stage where I am having the 'unloading geometry' problems. The scene (before I added the latest ForestPro object which does contain lots of flowers) rendered in about 10 minutes. With the addition of this new ForestPro object, I am at 50 minutes and it is still not complete because of the continual 'unloading geometry'.

Other than upping the RAM in my farm machines, what should I be looking at?

[flino2004]

I think vray always load the proxies when is needed per view....try dome light with BF for primary and none for secundary.

Fernando

[tricky]

Thanks Fernando

One thing I have done which has helped a lot is to convery the grass meshes into vrayproxies before they are added to the ForestPro object. I thought ForestPro did its own optimized memory management with meshes, but it seems that using vray proxies in there instead works a lot better.

[flino2004]

yes, it is better using meshes instead vray proxies for that situation. i got the same problem before and i resolved in that way, but it works great if you don't have too many different trees.
I read several times the same work flow in different forums specially for animations using domelight, BF and/or vrayambientlight.

Fernando

[3DMK]

ALWAYS turn your meshes to a VrayProxy before using Forest pro otherwise, it will create 500 3D trees crashing your system. When using a proxy it only loads one tree into ram.

[flino2004]

loading proxies is not the problem, if you use a mesh and instances is the same thing, you only load one tree.....the problem is when you have a lot proxies GI takes more time to be calculated than meshes....Proxies works well when you have a lot geometry and you want to save RAM but if RAM is not the problem using meshes is the right way to go in my opion. (Itoosoft did some tests using Proxies and meshes)

Fernando

[Itoosoft]

I would try to create clump of flowers, instead single elements, and use them in Forest. Testing with VRay, i have noticed a great performance hit when there are large number of small objects that intersect each other.

It seems that the VRay raycasting algorithm is severely penalized by the intersecting voxels (perhaps Vlado would confirm this). I don't know if this also has any impact over the memory requirements, but probably yes.

If that helps, in our website you can find a grass tutorial, which uses two nested Forest objects to create clumps of grass and scatter them. This way you can adjust parametrically both the clump and the full distribution, without recreating the mesh every time.

And only for clarifying, as Fernando has pointed out, Forest creates a single copy of each tree regardless of using meshes or proxies. The difference is the way that VRay handles each type of instance: the proxies are loaded dinamically from disk, and the meshes are stored permanently in memory. Each method has its own pros and cons.

[tricky]

I think vray always load the proxies when is needed per view....try dome light with BF for primary and none for secundary.

Fernando

I am using the vray sun/sky system for my lighting. Do you mean add in a vraydome light with its default settings and tweek to match my 'normal' settings?

[flino2004]

a dome light will be your skylight , because you set none for secondary bounces a dome will give you a better ambiental light distribution. You still need vraysun for direct lighting.

[Morne]

The difference is the way that VRay handles each type of instance: the proxies are loaded dinamically from disk, and the meshes are stored permanently in memory. Each method has its own pros and cons.

Could you outline the pros and cons of each please?

[Itoosoft]

Could you outline the pros and cons of each please?

Well, i have not a detailed list, but putting together some thoughts:

Objects:

- The geometry is loaded in memory while all rendering time (only a copy by tree model). This takes more space on the max scene, although you can solve it using XRefs.
- Any geometric object can be used as source, including parametric and animated objects (Onyx, GrowFX or other Forest object).
- The animation samples are generated on the fly, allowing to create endless animations, but this may be slow depending of the type of object.
- Some Forest features as Tint by Element only can be used with objects.

Proxies:

- The geometry is loaded/unloaded from disk dinamically, only when it is required for the current bucket. This optimizes the use of the memory, but usually is slower.
- The proxies doesn't take space on the scene, but they must be created manually before rendering. Also take care to make them visible to all render nodes.
- You can store the animation on the proxy file. It is much more faster to load the samples from disk, than generate them at each frame.

About the performance issue, usually the objects seem to render faster (at least on low/medium complexity scenes), but there are too many factors involved: memory specs, GI mode, local or network proxies... so each scene scene is a world. You should try several combinations to get the best result.

Anyways, i would be wrong in some concepts, because my knowledge of VRay internals and massive rendering experience is limited. I'm also here to learn VRay !