Vray RT vs Vray 3.0 Progressive Rendering

[soulburn3d]

Just looking for some clarification about these two features/products.

Currently, Vray RT lets us move around our objects and change lighting / parameters etc and see the viewport update the render in realtime. However, it isn't compatible with all max shaders / maps / objects.

Currently, Vray 3 has progressive rendering, but it happens in a second window, and you can't change position / lights / parameters and get an instant update of the render.

Would it be possible at some point to have a progressive renderer that updates in realtime and is compatible with all of max's features? (CPU only, of course).

- Neil

[Neilg]

I think that's just a feature complete RT, and they're working towards it.

[soulburn3d]

Well, but is the GPU the limiting factor? As in, because RT works on CPU and GPU, there's some things that will never work on the GPU, and so RT can never be feature complete?

- Neil

[vlado]

Well, but is the GPU the limiting factor? As in, because RT works on CPU and GPU, there's some things that will never work on the GPU, and so RT can never be feature complete?

Not at all.

The limiting factor is the 3ds Max architecture, which does not easily allow 3ds Max to be both in a rendering and interactive state - f.e. you can turn modifiers on/off just for rendering; objects can look differently in the viewport and in the rendering. Another example which is painfully demonstrated in many threads throughout the forum - if you so much as save the scene while a production render is going (as may occasionally happen with Autosave), this can wreak havok and make the file unusable or crash 3ds Max. Another problem are 3rd party plugins - f.e. imagine that a render is underway, using a FumeFX atmospheric and the user decides to delete or disable the atmospheric. We will get a notification only *after* the fact, so the most likely result is a crash as the renderer attempts to call a non-existing atmospheric effect.

The only way around this is to duplicate all render data in internal renderer structures - not only geometry, but also textures, lights etc - so that whatever happens to the 3ds Max scene does not directly affect the rendering until the renderer is in a state that allows these structures to be modified. This is f.e. what mental ray has been doing since day 1, and what V-Ray RT is doing. Some renderers have attempted to keep 3ds Max interactive while rendering; the result was extremely unstable and prone to crashes.

If you are a lucky Maya user though - the CPU RT engine in V-Ray 3.0 for Maya can render absolutely *everything* that the production V-Ray can

For 3ds Max, our goal for V-Ray RT is to continue to improve the support for the various features - f.e. light include/exclude, VRayEnvironmentFog, hair etc.

Best regards,
Vlado

[soulburn3d]

Thanks for the extended explanation vlado. I would have assumed that everytime you make a change in max, vray would just restart its render from scratch, and so you wouldn't hit these sorts of issues. But I suppose you could potentially change something in the scene, and before vray gets a chance to start the render over again, it hits one of those changes and all hell breaks loose.

The fact that you have to duplicate everything is a huge pain, that's one of the largest disadvantages of mentalray, so its a shame that you have to do the same to get the interactive rerendering to work. I guess no one on the 3dsmax team is willing to change the architecture to allow you to circumvent this issue

Guess I'll just have to live without it then, since plugins are so important to max's usefulness, and I would imagine it would be impossible to write vray translators for every max plugin out there, the job just seems too large.

Again, thanks for the extra info.

- Neil

[vlado]

I would have assumed that everytime you make a change in max, vray would just restart its render from scratch, and so you wouldn't hit these sorts of issues. But I suppose you could potentially change something in the scene, and before vray gets a chance to start the render over again, it hits one of those changes and all hell breaks loose.

This could work, but it must be implemented on the 3ds Max side, because 3ds Max must coordinate the render start/stop at the appropriate times - i.e. it must stop the rendering before the changes are made to the scene; wait for the renderer to finish; make the changes; and then restart. It must also tell the renderer exactly what changed between the stop and the start, so that the renderer can potentially update just the different parts of the scene and restart as quickly as possible. This is what Softimage is doing in fact, and while the implementation is far from perfect, it does a decent job.

The fact that you have to duplicate everything is a huge pain, that's one of the largest disadvantages of mentalray, so its a shame that you have to do the same to get the interactive rerendering to work. I guess no one on the 3dsmax team is willing to change the architecture to allow you to circumvent this issue

It is quite a bit of work and I think this was perhaps one of the goals of the whole XBR thing, but it seems that sadly that initiative ended up nowhere. In any case, we've implemented interactive renderers in Maya, 3ds Max, Softimage, web browsers, standalone apps and I'm still not sure what's the best way to approach it

Guess I'll just have to live without it then, since plugins are so important to max's usefulness, and I would imagine it would be impossible to write vray translators for every max plugin out there, the job just seems too large.

Which is why I'm hoping that one day 3ds Max would allow easier interactive re-rendering with the production renderer

Best regards,
Vlado

[soulburn3d]

Vlado, looks like max 2015 has had a lot of improvements in the activeshade area allowing iray to do progressive refinement rendering. Could these enhancements possibly lead to full vray doing Progressive Refinement using all standard max plugins?

- Neil

[vlado]

Could these enhancements possibly lead to full vray doing Progressive Refinement using all standard max plugins?

Unfortunately, not at all. iray, like mental ray and V-Ray RT, translates everything to its own internal data structures and does not use any rendering components directly from 3ds Max.

Best regards,
Vlado

[soulburn3d]

Yup, I'm aware of that, was just curious if the improvements may have accidently fixed some of the issues that require the translation phase I'll keep applying pressure to adesk and see what happens. Thanks.

- Neil

[vlado]

Yup, I'm aware of that, was just curious if the improvements may have accidently fixed some of the issues that require the translation phase

No, not yet there... also V-Ray RT still handles scene changes a lot better than iray/mental ray.

Best regards,
Vlado