IPR refection gloss issues with nightly builds

[francomanko]

Hi,

Here are 4 images, all IPR with latest and previous nightly builds, but not the stable release (which is fine), in maya 2017.

Is a sphere with vraymtl and a texture map assigned to the gloss channel. First 2 images, cpu and cuda are lit with domelight. Second 2 lit by 2 vray rect lights. I have attached the scene.

[yolov]

Thanks for the scene. Here's what I think happens: you're using Brute Force + Light Cache for GI and light cache is set to "from file".
In IPR mode we always use BF+BF, but for GPU only, we can use light cache from file. If the file path is wrong, i.e. V-Ray can't load the light cache, it will consider it "black" and that's why you would get a darker image.
You can use BF+BF, or BF+LC where light cache is set to single frame and it should render the same (when light cache is set to "single frame" for GPU, it will internally use BF+BF for IPR, but for GPU as production it will calculate the Light Cache).
Does this help?

[francomanko]

Hi, thanks for reply and yeah thats sorted it. (didnt realise the use file was checked).

On another point, i noticed that if the glossiness has a low value, i see the mesh edges of the sphere in the reflection channel, is this to be expected? (smoothing was set to 180 on the sphere)

[yolov]

This is reported to the developers and when there's any news, I'll let you know.

[francomanko]

awesome thx

[yolov]

I don't really know the maths behind it, but with low glossiness values you will most certainly always get such faceting and not only with V-Ray.
The thing is that with less geometry segments to the sphere, with high glossiness values, the fake smoothing of the normals (which makes the sphere look non-faceted with less segments) holds up, but starts to break with low glossiness values. In such cases, the only thing that you can pretty much do is add more segments (or subdivide the mesh) to produce more geometry and hide away the "artifacts".

[francomanko]

Hi, thanks for reply...yeah i really just wanted to check that this is expected. Having had so many bugs with maya 2017 to deal with I'm probably veering on the paranoid bug attitude Thanks for clarifying.