Vray testing times

[Soth3dlife]

Greetings! I am learning Vray at the same time I'm testing different scenarios and now I came across something that I don't know if it's normal so I was wondering if you could give me a hand with this:



It's a a 960x540

My DMC settings are:

Max 4
Min 1
Trheshold 0.005

Adaptive amount: 0.85

I've got two lights with 12 subdivision each

The spheres share the same shader which is a combination of a paintedCoat with 20 subds in Reflection and additive ClearCoat shader with no glossy whatsoever

I am using Irradiance and light cache and the render is 15 min...

I don't know what I am doing wrong but I am pretty sure that this render should be way faster. Can you give me a hand with this please?

[vlado]

It would be best to post the scene so that we can profile where most of the time is spent. It may have to do with the way the material is setup up, but it's hard to say just from an image.

Best regards,
Vlado

[Soth3dlife]

Here you have the scene:

https://dl.dropboxusercontent.com/u/...9/Revolver.rar

I cut down the renders to 5 minutes by turning off the ClearCoat layer...

[Soth3dlife]

Is it possible that because we have to use the shader item to blend shaders in an additive way, the render takes longer to render? I've read somewhere that Modo doesn't handle very well scenes with lots of Shader Items in the shader tree, although I have no idea if it affects in the same way to modo

[vlado]

Is it possible that because we have to use the shader item to blend shaders in an additive way, the render takes longer to render?

In theory it is possible, yes. Some optimizations that V-Ray can do for a normal blend, are not done when you use additive blend. I'm not sure yet if this is the case for your scene though.

Best regards,
Vlado

[Soth3dlife]

if you can check it out I'd really appreciate, This is something I work with everyday ( and my coworkers ) and It'd be awesome to be able to do it with Vray for Modo

[vladimir.nedev]

You don't have to use the "Add" mode when blending shaders. In fact it is better that you don't use it. Just set the reflection color
in the coat layer to 0.99, the "opacity" of its Shader to 0.5 and the blend mode of the "Shader" to "Normal".
For the base layer set the diffuse and reflection colors to 0.99. You will get almost the same final image but with correct GI.
If you use the "Add" mode the light in the scene increases with each GI bounce.

That's not the source of the slowdown in the scene though, still looking at it.

Can you upload the textures for the scene, most importantly the environment texture ? So I can test it properly.

Greetings,
Vladimir Nedev

[vladimir.nedev]

The slowdown is caused mostly by the cellular texture used for bump mapping. That scene would be faster in Maya or Max, if you connect
the blend material to a bump material, instead of having each material layer have its own bump material (that's what happens in modo),
since in that case the bump will be computed only once.

Still it would most likely be slower compared to using an image for the bump.

I see that you used different amounts for the bump in the base and coat materials. For the base it is -0.5mm and for the coat it is 5mm.
Was that your intention, or you thought that the "clear previous bump" option will make V-Ray ignore the coat layer bump amount ?

Greetings,
Vladimir Nedev

[Soth3dlife]

I actually I thought that option would ignore it, yes. Doesn't it?

[vladimir.nedev]

No, the option only makes V-Ray ignore any texture layers with the "bump" effect below the material. I have to check what modo does, and see if I could make it work the same way, for consistency.

If you set the coat layer bump amount to -0.5mm, it will make the bump very different and probably render faster since there will be less noise to anti-alias.

If you can use an image instead of the cellular texture, that would result in the biggest speed-up.

Greetings,
Vladimir Nedev

[vladimir.nedev]

Also turning off "Environment importance sampling" will speed-up the rendering a lot. When it is on, a dome light is created, while when "off" the GI from the environment is baked in the irradiance map.
If you don't have really bright spots in your environment image, the EIS may not be needed at all. And even if you do, you may turn it off while testing to get faster render times.

Greetings,
Vladimir Nedev

[Soth3dlife]

Got it! Thank you very much. I will keep that in mind thanks!!