HDRI on Quad Light

[lizGYM66]

I have an HDRI attached to a quad light via an image material in the color slot. How do I then rotate the hdri? 

[wernienst]

By rotating the light??

I'd say, the image map of a Quad Light is always limited to the quad dimensions.

[lizGYM66]

I was testing out a suggestion in the lighting tutorials which mentions mapping an hdri to a quad instead of using the skydome.

https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_for_3ds_max_ax_lighting_room_ax_quad_lights_ht...

It doesn't state that you can rotate it, but what would be the point otherwise?

[lee_griggs]

You might fare better by making them light portals and using a skydome_light (with a HDRI) instead.

https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_for_3ds_max_ax_rendering_maxtoa_ax_lighting_ba...

[wernienst]

You can't rotate the HDRI image, but you can move/scale it to your liking. However, the shadow casting will always be wrong.

[lizGYM66]

Hey Lee,

I was comparing the different noise levels between different options mentioned in the lighting tutorials so was tryin to avoid the skydome if poss.

So far I'm finding a quad, distant light and the sky works well but lord above it still requires a huge amount of rays per pixel. Anything below and noise is always present. 

3 lights samples each.

Is this typical to be able to clean the noise (attached)?

[lee_griggs]

Yes, unfortunately, interiors require a higher number of diffuse samples to clean up indirect noise. You could check AOVs to fine-tune this noise and where it is coming from. There is also denoising for IPR or final frame rendering.

If you could share your renders with timings/samples that could be useful for us to help you better.

[lizGYM66]

I had been using AOV's to check.

Attached is a unfinished test scene. What I tend to see blotchiness in the corners or dark areas using Noice. In this case its above the kitchen cabinets/wall.

I've payed with the Search radius but not to much difference. If I use Odin I don't get the blotchiness so much but it doesn't clean up edges as well, particularly in corners that have detail such as crown moulding etc.

In this scene are two quad lights outside the windows (no glass), 1 distant light and 1 extra quad for fill on the right.

Res 1000x1500px.

AA 6 (Adaptive AA 8 0.15 threshold)

Diffuse 4

Spec 2

Diff Ray Depth 6

Spec Ray Depth 2

Light Samples 3

I've attached the render, diff aov and ray counts from the log. Rendered in 39 mins on 32 core Xeon.

[lee_griggs]

Nice render, thanks for sharing. You seem to be on the right track. Are you using ACES color management?

Do you have a sheet of glass for the window? If so, enable caustics (standard_surface.advanced).

I am not sure Max AA: 8 would have much effect on the noise. You could try increasing it to see if it makes much difference. Diffuse_ray_depth of 6 seems quite high. I would have thought 3 would be enough.

[lizGYM66]

Using ACES but un-tonemapped with tone map and color correct imagers instead.

No glass in the window.

So I'm on the right track here then and not missing anything obvious? FWIW Corona also struggles with that area above the cabinets to.

[lee_griggs]

Yes, it's a common issue with path tracing. I would increase the number of diffuse samples for the corner noise. 4 seems quite low. It will increase your render times though.

[lizGYM66]

So it seems like 6AA and 5-6 diffuse is where you have to be at the very least?

[lee_griggs]

It depends on the scene, but for interiors that sounds reasonable. 

The ARV window has a Debug shading mode that allows you to render just shading (you can also disable textures etc. in the Diagnostics tab) that allows you to focus on setting sample settings without being distracted by textures etc.