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One of the great things about lighting with V-Ray is the versatility and diversity of the tools available to us. As well as the natural daylighting system and the ability to mimic artificial light sources, we also have the option to use image-based, or HDRI, lighting if we want to. The initials HDRI stand for High Dynamic Range Image. This is a specialized image format that holds far higher amount of data, including luminance data, that can't be captured by typical film or digital cameras in a single shot.
In this video we are not only going to walk you through the steps required to set up image-based lighting, but we will also demonstrate to you a little trick that can add some directional light back into our renders. This will allow us to compensate for the lack of strong directional light that we typically see in image-based lighting. Our start scene is pretty much the same as our earlier sun and sky setup. We are starting with an artificially darkened environment. We also have Global Illumination and the V- Ray Physical Camera at work, including use of Exposure control.
It is true that many V-Ray for SketchUp artists like to work with Exposure disabled when producing IBL renders, but as working with the V-Ray Physical Cameras Exposure controls can be an art in and of itself, I typically prefer to work with Exposure on as much as possible. Practice, as they say, makes perfect. To create our image-based lighting setup, the first thing we need to do is open up the V-Ray Options dialog for ourselves. So if we come up to the toolbar, we can click on the Options dialog icon and open it up.
Next we need to access the Environment rollout, so let's left mouse-click just to open those controls up. And we are going to be working with the Global Illumination (GI) Color option, so let's put a check in the box just to turn those on. To add the image for our lighting, we of course need to come into our map slot and in the Texture Editor, use the dropdown to access the TexBitmap. This means we can now attach a bitmap file to be used by V-Ray. We can do this by using this File slot.
As with IES files, there are lots of sites around the Internet that offer free high quality high dynamic range images, ones that can even be freely used in commercial work. The two that I will be using are from the free sIBL set entitled BasketballCourt, downloaded from hdrlabs.com; you can of course use any HDRI file of your choice. The image that we will be adding into this lighting slot is actually a much smaller in terms of resolution and blurred version of the original HDRI.
Smaller size means that less memory will be used during the rendering process and the blurring ensures that we get smooth lighting in our environment. We will be free from any small noise problems. Add our image, let's click on the swatch. Navigate to where we have our HDRI saved and then just add our lighting image into the control slot. Now before we exit out our Texture Editor, there is one tweak that we need to make to the parameters in here, if we come up to the top you can see we have this UVW Type option.
In here, we need to use the dropdown to switch from UVWGenChannel to UVWGenEnvironment. This just tells V-Ray that the image file we're working with is not for texturing with, but is to be set as an environment map. Depending upon the format of the HDRI we are working with, we may need to make a change to this mapping type. You can see in the drop down we have a number of options available. As our map is indeed spherical, we can just work with the default. One of the settings worth pointing out is this Horizontal Rotation value.
If we want to rotate the lighting in our scene, then we can do so by means of this bitmap control. as we're finished with our lighting setup, we can just OK to exit out of the Texture Editor. Of course, we may want to add our High Dynamic Range Image as the background for our render at the same time as setting up the lighting. To do that we can just put a check in the Background (BG) Color option, coming to the map slot, find our TextBitmap node and this time add our full High Dynamic Range Image into the control slot.
Naturally we don't want a blurred background image for our renders. Again, we need to come and make a change to our UVW Type and switch that over to Environment. Now we can click OK, exit our Options dialog and see what we have by way of scene lighting. What we get of course is now an illumination setup and a backdrop to our renders that match one another perfectly. We can see coloration matches and we can see illumination shifts that really are very nice indeed.
Do keep in mind that the settings for our Global Illumination controls are very low indeed in terms of quality. We just want nice quick test renders at this moment in time, so if we wanted to clean up some of the noise that is present in the scene, we could certainly go and improve things by means of our GI controls. However, one thing that our GI controls will not fix is the fact that we really are missing any strong directional light in the scene. You can see that we do have a sense of the direction of the light as our shadows are just traveling away over to the left-hand side of the image a little bit being cast by our table object here, but still we don't see anything that would convince us that we have sunlight in the scene.
Certainly in terms of directional light our rendered image is not matching what we see in the backdrop. Of course, we cannot add our V-RaySky map into the equation s that we can use the sunlight plug-in there, because well our slots are both taken by our High Dynamic Range Image. All is not lost however, because we can play a little trick inside of V-Ray for SketchUp. If we just come back to the Options dialog, we can come into the Global Switches rollout and you see here we have this Default Lights option.
This allows us to enable or disable the default lights in the scene. Now in SketchUp the default light is the sun. This means if we put a check in this box, we have essentially turned sunlight on in the scene. The problem we have is that because of our current Camera Exposure settings our sunlight would very much overpower the scene; it would totally wash out our HDRI lighting. There are a number of ways we could try to tackle this problem, the simplest of which is the one that we will use, which is to simply alter our current Exposure settings.
So let's first of all close-up our Global Switches rollout and open our Camera rollout. In here you'll notice that we have our Film Speed or ISO value set fairly high. This is really to bring out the lighting in our HDRI. And fortunately it would also contribute to our sunlight being extremely bright at this moment in time. So let's set this to a value of 100. Of course, now our image based lighting will be subtle in the scene as to not really be seen. It would not contribute enough to get a nice natural look to our light setup.
To compensate for that fact we can close our Camera rollout and we can just use these multiplayer values inside of our Environment controls. In this instance I am going to set these to a value of around about 16. That should take care of things very nicely, of course you can set these to suit. Again, we'll close our Options dialog and see what kind of a change we have made to our lighting setup. What we get now is of course a very natural looking daytime light setup in our scene.
We still have the subtle shifts in skylight illumination coming from our High Dynamic Range Image, but at the same time we have nice strong directional light coming from our sun. If you're finding that the directional shadows in your scene, the shadows coming from your sunlight are not really matching up with those coming from you High Dynamic Range Image, all you need to do is use SketchUp shadow controls to alter the position of the sun in the sky. That way you can very easily match the two sets of shadows up. As we've many things in the V-Ray, getting image-based lighting up and running is a quick and easy process once we know how it is done.
The end result is oftentimes a subtlety of lighting that would be very time consuming to set up, if indeed at all possible, using any other methods.
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