How To Get Identical Results with Dome Light and GI Environment

[soulburn3d]

So if I place an HDRI in the GI Environment of the Environment rollout of the Render dialog, I get smooth looking results on my object. If I use that same map in a vraylight set to dome, I get very noisy results. What settings do I have to set the dome light to to get the same results as the Gi Environment? I assume I need to increase the sampling subdivs of the domelight, but if you know exactly how much I need to get identical reuslts that would really help. Thanks for any advice.

- Neil

[Dariusz Makowski (Dadal)]

Its bit more complicated. With dome light you get direct light with override you dont. You also get specular which you dont get from override. So you are missing a lot of real physics when you not have dome light.

As an alternative you can also use vray light with skylight enabled.

[soulburn3d]

Now that's confusing. What do you mean by you don't get direct light with override? If I put an HDRI in the GI Environment, I do have to turn GI on to get it to work, but then my surface does receive direct light from the HDRI, not just bounce light. As for specular, I assume you mean that with the GI Environment, it doesn't transmit specular reflections, whereas it does with a vray light set to dome (unless you mark the vray light as invisible).

- Neil

[vlado]

Generally you just need to raise the subdivs of the dome light until the noise goes away.

Best regards,
Vlado

[Dariusz Makowski (Dadal)]

Now that's confusing. What do you mean by you don't get direct light with override? If I put an HDRI in the GI Environment, I do have to turn GI on to get it to work, but then my surface does receive direct light from the HDRI, not just bounce light. As for specular, I assume you mean that with the GI Environment, it doesn't transmit specular reflections, whereas it does with a vray light set to dome (unless you mark the vray light as invisible).

- Neil

Umh u lost me...

IBL generates:
Diffuse light
Specular
Reflection
Refraction

Override generates:
GI
Reflection
Refraction

Light using skylight:
Diffuse
Specular
Reflection
Refraction

I've rendered examples in zip below.
JPEG.zip

Hope this helps.

If you want smooth results as usual increase light/mateiral/etc samples...

Edid, Vlado/chaos is there any reason why when using light+skylight my specular pass appears to have clamped specular?

[soulburn3d]

Generally you just need to raise the subdivs of the dome light until the noise goes away.

Best regards,
Vlado

Thanks Vlado.

- Neil

[soulburn3d]

DADAL,

If I make a teapot on a plane with a 100% white color, then set the GI environment to white and render, then I get a white teapot and plane with slight darkening under the teapot.

If I then take the same scene, make a vray light set to dome, make it spherical, set multiplier to 1, make it invisible, and render, I get an identical render (noisier, of course).

So that's what I mean, they both provide direct light and bounces. It's just you have to turn "Enable GI" on to see the direct light of the GI environment. Whereas you get direct light with the vray dome light even without turning GI on. So your chart is correct, you get "GI" with the override, but the GI includes Diffuse light and diffuse bounces.

- Neil

[Jorq1H]

DADAL,

If I make a teapot on a plane with a 100% white color, then set the GI environment to white and render, then I get a white teapot and plane with slight darkening under the teapot.

If I then take the same scene, make a vray light set to dome, make it spherical, set multiplier to 1, make it invisible, and render, I get an identical render (noisier, of course).

So that's what I mean, they both provide direct light and bounces. It's just you have to turn "Enable GI" on to see the direct light of the GI environment. Whereas you get direct light with the vray dome light even without turning GI on. So your chart is correct, you get "GI" with the override, but the GI includes Diffuse light and diffuse bounces.

- Neil

Try adding VrayLighting and VrayGlobalIllumination as render elements when doing these tests and you'll see how Vray treats the different methods. As DADAL says, when doing IBL from override you only get indirect light. This is the reason the lighting is smooth, but also the reason why you won't get the nice, sharp direct light and shadows. When adding the HDRi into the VrayDomeLight, add more shadow samples and the noise should go away. To get faster, nicer and more balanced lighting with this method, I recommend our own Akin Bilgic's Vray Optimization Guide which step-by-step shows how to get the best results with these lighting setups (and most others).

[soulburn3d]

As DADAL says, when doing IBL from override you only get indirect light. This is the reason the lighting is smooth, but also the reason why you won't get the nice, sharp direct light and shadows.

Could you post an example where IBL gives you sharp direct light and shadows? Because again, if you render using both methods for me they provide identical results in all the scenerios I've tried (solid color, HDR image, etc).

- Neil

[Dariusz Makowski (Dadal)]

Could you post an example where IBL gives you sharp direct light and shadows? Because again, if you render using both methods for me they provide identical results in all the scenerios I've tried (solid color, HDR image, etc).

- Neil

Its in the zip file I send I posted early in this topic... Just open it up and go over images you will see the difference between override and Dome...

[soulburn3d]

So for example, do you mean the extra darkening happening between the images "Dome.lighting.jpg" and "Override+GI.GI.jpg"? If so, I didn't see that in any of my renders. Let me do a few test renders tonight and post em.

- Neil

[Dariusz Makowski (Dadal)]

There is also noticeable difference in shadow sharpness, blotchy GI samples and so on if you look at those 2 renders as well as lacking specular component when using GI override solution and so on...

[Jorq1H]

Could you post an example where IBL gives you sharp direct light and shadows? Because again, if you render using both methods for me they provide identical results in all the scenerios I've tried (solid color, HDR image, etc).

- Neil

I didn't say you'd never get sharp shadows with indirect light, but working with high res hdr's with bright spots can be a hassle without the domelight. Below are two very simple renders, first one with direct light, the other with indirect light only:



To get the sharper shadows with this hdr and indirect lighting I had major issues with splotchiness regardless of how much I upped the samples. It's probably some to get the full dynamic range from the hdr as indirect light, but I didn't get satisfying results. And of course, this will vary from hdr to hdr.

[soulburn3d]

There is also noticeable difference in shadow sharpness, blotchy GI samples and so on if you look at those 2 renders as well as lacking specular component when using GI override solution and so on...

Well, I get the lack of specular reflections, since it doesn't provide anything to reflect. And I get the blotchiness since the samples on the vray light are kind of low. But I hadn't noticed in my tests the shadow sharpness issue. Again, will do some test renders tonight and see if I can replicate them.

- Neil

[soulburn3d]

I didn't say you'd never get sharp shadows with indirect light, but working with high res hdr's with bright spots can be a hassle without the domelight. Below are two very simple renders, first one with direct light, the other with indirect light only:

To get the sharper shadows with this hdr and indirect lighting I had major issues with splotchiness regardless of how much I upped the samples. It's probably some to get the full dynamic range from the hdr as indirect light, but I didn't get satisfying results. And of course, this will vary from hdr to hdr.

I have to admit that the more I think of it the more the terms direct and indirect light are too nebulous. For me as an artist, I read direct light as light coming from the light source and hitting a surface (whether that light source is a tranditional cg light or the sun painted on an hdri), and indirect light means light that comes from a surface and hits another surface (or bounce light). From what I remember back in the old Brazil days, the reason a skylight (or in vray, the GI Environment) is considered indirect light is because the light is "bouncing" off the environment and then striking the objects in your scene. But as an artist, an hdri, while technically an environment, isn't an object and so should be considered a direct light source and not a bounce light source.

My brain hurts

- Neil