For the layman – How 3D Rendering Works. Part 9: Post-processing

[ about a 15 min. read ]

Well we did it. We went through the whole process. We got a 3D model. Materialized it. Added textures. Edited UV maps. Set up the camera composition. Added proper lighting and we rendered our image. So now we are done right? No. Not yet. Now comes the final part. And it is actually a real make or brake part of the process. It is time for the post-processing.

1. What is post-processing?

Post-processing is, as the name already suggests, the whole process of editing our render to improve its look, after (post) the initial render has been made. Hence the name post-processing. It consists mainly out of 2 steps. It is the color correcting of the image and the color grading of the image.

2. What is color correcting?

Color correcting is the process of… well… correcting the colors of the render. If you would normally have a render from a 3D render software, the image tends to look a little flat. This is because there is not a lot of contrast in the rendered image. Parts that are supposed to be black, like in dark shadow area’s, might not be completely black. And parts that are white, like highlights in reflections, might not be so bright as they need to be. So the process of color correcting is to correct the colors so they cover the full spectrum of the visible color range. From the blackest blacks, to the whitest whites, and all the colors in-between.

Taking the binoculars again as an example. The image below compares the initial render we get from our rendering software to the color corrected image. In the colored corrected image, the light exposure had been increased and the contrast has been corrected. You can see that the color corrected image makes use of a better distribution of the colors in the color spectrum, and that more has become visible in the shadow parts. This makes the image look less flat than before.

After the color correcting, it is time for the color grading.

3. What is color grading?

Color grading is the process where you give the image your personal touch. With color correcting, it was more about correcting the image to a correct real world color distribution. But with color grading you are going to tweak the image towards a more personal preferred artistic color style. This could be anything. You can maybe make the image black & white:

Or maybe a more old school sepia look:

Or maybe give it a more dramatic color effect:

You get my point. It is the more artistic process of the post-processing step. It does require that you first perform a proper color correction. That is always important.

A term you might also come across when you are looking into color grading is that artists use so-called LUT’s. This is the abbreviation of Look Up Table. It is basically a preset for a certain color grading look that they can use in their software to quickly give their renders a specific stylized look. Like I actually did with the 3 examples I showed above.

4. Adding my personal color grading touch

Step 1. Adding contrast and color intensity

In my images I have my own personal preference on how to edit them. I first prefer to make the colors pop more by adding additional contrast and color intesity.

Step 2. Increase sharpness

Often I like to increase sharpness a bit. To make details a bit more crisp. Most of the time this step is just a subtle change. Maybe not even that noticeable in the comparison below. But the leather texture on the grips does become a bit more pronounced.

Step 3. Add ambient occlusion shadows

Then I like to add some Ambient Occlusion shadows. These are contact shadows and additional shadows in nooks and crannies. They make sure that an object is a bit more grounded. In 3D rendering these Ambient Occlusion shadows are actually made using a separate render pass. Be sure to keep an eye out on my blog, if you want to know more about Ambient Occlusion and how it is made. As I will be posting a separate article about this soon.

Step 4. Maybe go a bit crazy?

I would normally stop at step 3. But for the gist of it, I could do a little bit more. Like for example add chromatic aberration (color fringing around an objects borders), vignette (darken the corners of an object to add focus to the subject in the center) and dust particles. Then we end up with something like this:

That concludes this “For the layman” blog series. I really enjoyed making it. And I hope you just as much enjoyed reading it. And most of all, I hope you learned something new. Be sure to keep an eye out on my blog, as I will be posting way more topics to demonstrate the absolute power of 3D rendering, and to break down some of the more advanced techniques that I use.

As always, let me know if you have any questions or comments below.

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