glass rendering - tips and tricks

[pgrochola]

Hi,

I'm rendering lots of fractured glass geometry close to camera, full screen.

It's around 50,000 primitives plus particle instances (another 80,000 primitives for very small pieces).

Please see attached image.

My setting:

Currently I'm using one area light using a transparent shadow (2K) and rendering using the raytrace render engine.

No motion blur needed.

Will probably do depth of field in post.

Default ray and pixel sample setting at the moment.

Using the default glass shader in H11.0.775 (only change to default is disconnecting the displacement inside shader)

Result:

At HD (1920 X 1080)it's taking around 1 hour (on a dual quad code xeon running at 2GHz)

I can see some noise and shadows res is too low so it will only go up from here.

Obviously, I have 1500 frames so render time is very important.

Questions:

- Is that as quick as it's doing to go for something like this?

- Can anyone give me some optimization tips?

- Would you guys recommend PBR? I'd love caustics but my initial testing showed PBR to be prohibitively slow.

I really can't go too far over 1 hour a frame.

- What kind of render time would I be looking at going with PBR at "optimized settings"?

- I went with the raytrace engine because micropolygon rendering suffered from noise (I had to reduce the "noise level" which made my render time sky rocket). Am I missing something here?

Transparent Shadows:

I notice with transparent shadows that the darkness of the shadow changes as the geometry rotates.

It happens when the normals of the surface point away from the light at certain angles.

This can look a bit strange (please see attached image).

Thanks very much for the help!