Finishing a 3D Render: Color Grading, Bloom, and Effects

A Post Production Checklist for CG Artists - Part 2

Welcome back! In the second section of this series, we'll continue exploring post-processing workflows for 3D artists, this time focusing on color grading, bloom, and lens effects. If you missed part-one, jump back and check it out right here.

Great! Let's continue:

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Dial in Your Contrast and Color Grading:

This is an absolutely essential step—it doesn't matter how well you've tuned your colors and contrast inside your 3D package, they can be better.

At the very least, you should be familiar with using Photoshop's various adjustment layers: Brightness/Contrast, Levels, Curves, Hue/Saturation, Color Balance, etc. Experiment! Adjustment layers are non-destructive, so you should never be afraid to push things as far as possible. You can always scale and effect back, but you'll never know whether it works until you try it.

One of my favorite color-grading solutions is the often overlooked gradient map—it's just a gem of a tool, and if you haven't experimented with it you should should do so immediately! The gradient map is an excellent way to add warm/cool color contrast and harmonize your color palette. I personally love adding a red-green or orange-violet gradient map to a layer set to overlay or soft light.

Finally, consider that there's life beyond Photoshop when it comes to color grading. Lightroom actually has a lot of options and presets for photographers that Photoshop simply doesn't give you access to. Likewise for Nuke and After Effects.

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Light Bloom:

This is a nifty little trick that arch-viz studios use all the time to add some drama to the lighting in their scenes. It works amazingly well for interior shots with big windows, but the technique can really be extended to any scene where you really want little patches of light to jump off the screen.

An easy way to add some bloom to your scene:

Create a duplicate of your render. Place it on the top layer of your composition and change the layer mode to something that lightens your values, like overlay or screen. At this point, the whole composition will glow, but your highlights will be blown way beyond what we're looking for. We need to scale this back. Switch the layer mode back to normal for the time being.

We only want the light bloom to occur where there are highlights, so with the duplicate layer still selected, go to Image → Adjustments → Levels. We want to push the levels until the entire image is black except for the highlights (drag both handles toward the center to achieve this).

Change the layer mode back to overlay. The effect will still be exaggerated beyond what we're after, but now we can at least control where we want it.

Go to Filter → Blur → Gaussian, and add some blur to the layer. How much you use is up to you, and really comes down to taste.

Finally, we want to scale back the effect a bit by changing the layer opacity. Again, this comes down to taste, but I usually dial the bloom layer's opacity down to approximately 25%.

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Chromatic Abberation and Vignetting:

Chromatic abberation and vignetting are forms of lens distortion that are produced by imperfections in real-world cameras and lenses. Because CG cameras have no imperfections, chromatic abberation and vignetting will not be present in a render unless we explicitly add them ourselves.

It's a common mistake to go overboard on vignetting and (especially) chromatic abberation, but used subtly they can work wonders on an image. To create these effects in Photoshop, go to Filter -> Lens Correction and play with the sliders until you achieve an effect you're happy with.

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Noise and Film Grain:

I absolutely love dropping in a little bit of noise or film grain to finish off a shot. Grain can give your image a very cinematic look, and help sell your image as photoreal. Now, obviously there are certain shots where noise or grain might be out of place—if you're going for a super-clean look this is something you may want to leave out. Remember, the things on this list are simply suggestions—use them or skip them as you see fit.

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Bonus: Bring it to Life:

without adding a whole lot of overhead to the workflow.