Join Brian Bradley for an in-depth discussion in this video Controlling reflectance through color values, part of Mental Ray: Control Color Bleed in 3ds Max.
- [Instructor] Having given ourselves a bit of insight into just what color bleed is and how it is created, time now to make a start at examining the various ways in which we might go about controlling this in our renders. Of course, the first thing that we should probably do here is go ahead and hit the render button so that we can see just what our room looks like before we go ahead and introduce a color bleed problem. What we get is a very clean render indeed, with barely a hint of color bleed in sight. Of course, all of this would change if we suddenly decided to give our wood floor here a coat of red matte paint, which we can actually do by jumping into the material editor and after clicking on the diffuse color swatch for the floor material, set the saturation value to 0.8 and click OK.
What we want to do now is open up the RAM player in Max, save what we have into the A Channel, and then go ahead and render again. What we see if we add our new render to Channel B in the RAM player is that we now have a very definite color bleed problem for sure, one that we need to set about learning how to control. Now one thing we might begin to think here is that color saturation is where our problem lies. Well, whilst it will indeed effect our color bleed problem, it isn't really the best control mechanism that we can use.
To show what I mean, let's jump back into the material editor, drop the floor material saturation value from 0.8 to 0.2, and then render again. Now whilst the walls, window area, and ceiling all see a definite reduction in color bleed, we no longer, of course, have anything like a red floor in the scene. In fact for all intents and purposes, a client or a supervisor would probably say that it was now back to its original grey color. Instead of working with the saturation value then, what we want to do is instead drop the value perimeter from 0.5 down to 0.3, effectively giving ourselves a darker red floor.
Let's reset our saturation to 0.8 and then render again. What we get now if we add this to Channel A in the RAM player, is a definite reduction in the amount of color being bled onto our walls and ceiling. This occurs because following the principles outlined in Chapter One, darker-looking surfaces are actually reflecting less of the light that is striking them. Less light being reflected means, of course, that less color is being carried around our environment.
Indeed, to get the best of both worlds from this particular physically-based approach to color bleed control then, we will probably want to keep both the saturation and value perimeters in the color we're using as low as we possibly can without of course sacrificing either the look or mood that we are trying to create. Let's make one final set of tweaks then, and set our saturation to 0.7, the value to 0.4, and then, after taking another render, again compare to our fully saturated version.
Now whilst the differences here aren't overly dramatic, we can see that by some careful choosing of values inside of our color swatches, we can definitely reduce the amount of color bleed being thrown around our environment.
- Controlling reflectance
- Understanding how geometry setup affects color bleed
- Choosing color placement carefully
- Using the FG Diffuse Bounce control and Photon Energy setting
- Controlling color bleed via object property controls
- Using the rayswitch map