What the color mapping modes do

- Having taken a look at some of the lesser-used controls that can be found in V-Ray's color mapping options, time, in this exercise, for us to take a look at how the various color mapping modes available in the type drop down actually affect the color values that are being produced in our final rendered images. Now for the sack of speed we are, in this video, going to be making use of some pre-rendered images that have been opened up in the V-Ray frame buffer window and then saved to the history list. All of which you of course have access to in the render output folder of your Exercise Files download.

These just help us make an examination of the differences that each color mapping mode brings to the table. To help even more with that, we will in fact be looking at our images here with the display colors in sRGB space button in the V-Ray frame buffer window turned off. In other words, we're going to be looking at the actual linear renders originally produced by V-Ray. With the default of Reinhard set then, this is how things currently look in our scene. Reinhard is actually a hybrid color mapping mode that gives us the ability to blend between the exponential and linear multiply modes that V-Ray also makes available as separate options.

The parameter controlling the blend is this Burn value with it set to 1.0. The resulting image as we see it here will be 100% Linear multiply and with the Burn value set at 0.0. So our next image, the result would be a completely exponential render. And of course if we set the value at 0.5, we get an exact half-way blend between the two. Not the interesting thing we can note as I switch between these three images is the difference the color mapping change makes to the brighter areas of the scene.

With the straight linear multiply option, we get some very over-bright or burnt looking areas. And indeed if I right click and use the color picker, you can see that we have a number of super bright areas in the image. Whereas in the exponential render, our white values are nowhere near as bright. In fact if I set the linear and exponential renders as the A and B sources in the frame buffer, you can see as I wipe between them the huge difference that this color mapping change makes. Now whilst Reinhard is the default color mapping mode in V-Ray, it is of course by no means the only option available.

If we take a look in the color mapping Type drop down, we see the first option, given it was V-Ray's previous default, is Linear multiply. This is a mode that basically takes each of the color values sampled from the scene and then multiplies them all together based on brightness levels found in the sample information. In other words, it is a what-you-see-is-what-you-get mode, making no changes at all to the color values that have been calculated internally by V-Ray. Hence the tendency as seen in our first Reinhard image here to get over-bright or burnt areas in the render.

Exponential, on the other hand, as seen in the second Reinhard render that we looked at, deals with that problem by working to keep the brightness levels inside a particular range and instead applies an increase to color saturation. Rather than having brighter pixels in images then, what we get are more saturated ones. Which as we can see does help eliminate over-bright areas in the render. Not that this mode is without its own problems, of course. As a consequence of applying value changes to saturation instead of brightness, we can tend to get images that look a little weak or washed out.

For that reason we may instead choose to work with the next mode available in the drop down, this being HSV exponential. In this mode, if I just load that image up, rather than pushing color saturation, which will of course tend to lighten color values, HSV exponential actually works to preserve the existing hue and saturation of the colors it encounters, essentially keeping everything within a particular tolerance. One problem a number of artists have with this mode though is that the preservation of color saturation can tend to make the renders feel a little unrealistic.

Our brains expect bright areas inside a render to be somewhat desaturated, particularly so when we perceive that a high amount of light energy is meant to be present. For this reason then we may want to swich over and use Intensity exponential which if I just load that up does give us some of those brighter areas back. Intensity exponential is working to preserve the ratio of the RG and B color components. In other words, it is doing its best to keep the original colors in balance.

Meaning we get a more expected ramp-up and fall off of RGB intensities as objects move toward and away from bright light sources. This means we can also have values above 1.0 in our renders, which isn't something that the HSV exponential mode allows. The final two color mapping options in the drop down, Gamma correction and Intensity gamma, are in fact legacy options that exist from a time when V-Ray didn't have a gamma parameter available for all of its color mapping modes.

These then were added as a means of applying Gamma correction to an image if it was needed or wanted. As all we really get from them is a straight Linear multiply effect, I haven't included renders for them here. Because our use of color mapping controls then will affect not only the way our images look once rendered but also to some extent what we are able to do with them in post-production, it is important that we make good color mapping choices according of course to the needs of our current project. In fact, understanding all of the critical concepts that we have discussed in this chapter, although possibly a little on the dry side, will go a long way towards helping us make good choices when working with V-Ray in general.

Choices that can improve not only the quality of our finished work but that can also bump up our productivity levels as well.