HDRI with VraySun or without?

[D C]

I've always been taught that when using a HDRI in your scene, you should align it's sun to a Vray Sun using the horizontal rotation slider within the Vray HDRI material.

 

I've come across some tutorials online however, that do not follow this method - and use a HDRI alone to light the scene. No Vray sun used at all.

 

Is there any particular reason for this? We primarily do exterior images.

 

Cheers

Edited January 18, 2016 by Dan.Corris

[nejck]

Based on my understanding, if the quality of the HDRI is high then the sun on it will be strong enough to produce good, accurate shadows. If not, well then you can help yourself by adding a V-Ray sun to kind of enhance the effect of a sun being present. Quality HDRIs usually have more information in them ala the sun power is still there once you go to really low exposure values (this is just an example).

 

Also, combining HDRI + a V-Ray sun might give you more control over everything but then again, you need to adjust your values accordingly so as to not overpower the HDRI effect.

 

That is my take at least

[D C]

Based on my understanding, if the quality of the HDRI is high then the sun on it will be strong enough to produce good, accurate shadows. If not, well then you can help yourself by adding a V-Ray sun to kind of enhance the effect of a sun being present. Quality HDRIs usually have more information in them ala the sun power is still there once you go to really low exposure values (this is just an example).

 

Also, combining HDRI + a V-Ray sun might give you more control over everything but then again, you need to adjust your values accordingly so as to not overpower the HDRI effect.

That is my take at least

 

Thanks for this

 

They are of a high quality most definitely and shadows etc are on point. You mention exposure at lower levels, I assume its correct to increase the camera exposure to compensate for lower light levels in the scene? i.e. obviously not having a Vray sun present in addition to a HDRI means there is less light being generated. I'm usually set with an F-stop of 10-14 with both a sun and HDRI, but using a HDRI alone I'm at F-stops of 2 minimum. Is this normal/expected? Would one look to increase the render multiplier within the Vray HDRI material too?

[Chris MacDonald]

I use one or the other, not both.

 

As said in the previous post, if the HDRI is of sufficient quality it should be able to light the scene and cast good shadows with ease. If you are still struggling with the sharpness of your shadows, try playing with the gamma of the HDRI.

 

As for camera exposure just think of it as you would in real life. Are you going to be able to use the same camera settings at dusk as you would on a bright sunny afternoon?

[inpow watir]

Thanks for this

 

They are of a high quality most definitely and shadows etc are on point. You mention exposure at lower levels, I assume its correct to increase the camera exposure to compensate for lower light levels in the scene? i.e. obviously not having a Vray sun present in addition to a HDRI means there is less light being generated. I'm usually set with an F-stop of 10-14 with both a sun and HDRI, but using a HDRI alone I'm at F-stops of 2 minimum. Is this normal/expected? Would one look to increase the render multiplier within the Vray HDRI material too?

 

The reason people inventing/ using sun or other directional light together with HDRI Dom lighting is to overcome the unsharp shadow problem that usually arise whenever use hdri map. In order to get a sharp shadow in case gamma inverting option is not helps much. Because many of hdri light source usually diffused therefore the shadow is not too obvious whenever one need that fx in their scene.

To get more lights to match your aimed exposure on hdri-only approach (other than tuning your camera exposure) you can do two ways:

1. Using render or overall multiplier option on material slot, or

2. Using the light multiplier itself (at the dome)

 

One thing you need to remember is NOT every hdri GI setup needs an additional sun or direct light, some is some is just does fine.

Edited January 19, 2016 by inpowwatir

[D C]

Cheers everyone!

[inpow watir]

You are welcome

[Jason Matthews]

I primarily use HDRIs to light the scene and for the background image. I copy the HDRI to the background so that I can adjust the settings independent of the lighting. Then between the camera exposure and the HDRI used in the GI I get nice results.

[Guest dialog]

Whatever makes your image look nice

[nejck]

Thanks for this

 

They are of a high quality most definitely and shadows etc are on point. You mention exposure at lower levels, I assume its correct to increase the camera exposure to compensate for lower light levels in the scene? i.e. obviously not having a Vray sun present in addition to a HDRI means there is less light being generated. I'm usually set with an F-stop of 10-14 with both a sun and HDRI, but using a HDRI alone I'm at F-stops of 2 minimum. Is this normal/expected? Would one look to increase the render multiplier within the Vray HDRI material too?

 

People before me already answered this one but my two extra cents to this debate would be that yeah, try sticking to the values that are deemed "believable". It is normal to tweak them up and down, left and right but just for the sake of keeping things somewhat averaged I tend to stick to the more realistic values - I suppose this might help in translating materials you develop from one scene to the next.

 

Do note that sometimes you have some extra exposure control in the VFB / Picture viewer that can affect your final image.

 

To summarize, plunge that HDRI in, try to work the camera and just find that composition you are looking for Happy rendering, Sir!

[re vit]

There's no need in extra VraySun. Just open exr file in Photoshop, steal the color value in the center of the sun but pump up the value to +6-11 stops; then make one touch of round brush with say 90% softness in the center of the sun (to find it, you should lower the exposure`display slider).

Save and reload,- now you've got perfect shadows.