CINEMA 4D MATERIAL TEST – R18S AMBIENT OCCLUSION INVERT DIRECTION

November 9, 2016

As the CG world keeps evolving towards realism, the importance of texturing remains a key to achieving your vision. Here’s my basic knowledge walkthrough of this Cinema 4D material test.

 

Using Cinema 4D and the Physical renderer, I wanted to start pushing my understanding of material workflow for 3D. This is a walkthrough of a very basic test, and my comfortable workflow in 3D. Rather than spending hours modeling something worth rendering, I’ve started gathering free assets from ThreeDScans.com. Using free assets for practice is much more straight forward, and eliminates the dread of never finishing your test. The faster you can get to practicing what you’ve set out to practice the better. After adjusting some framing and composition options, I landed here.

 

Viewport Render in C4D

 

Since this model is a 3D scan, I have the benefit of starting with lots of detail that doesn’t need to be textured in. The down side of that is this is a very high poly mesh. Thankfully we work on pretty industry standard iMacs, but the poly count is worth noting for rendering later.

 

My initial goal was to create a Jade like material to test out and understand C4D R18’s new “Inverted Direction” option in the Ambient Occlusion shader. Normally, AO looks at the faces along the outside of the model, and adds shading based upon how close faces are to each other, or how acute the angle between faces is. Exampled here:

 

 

The “Invert Direction” option, tells it to look not along the surface, but back inside the model, and check for faces that are close and angles that are more acute.

 

 

This can achieve an effect similar to sub-surface scattering, without the hit of render time. While it’s more of a hack than an alternative, it’s a good tool to have in your pocket nonetheless. Below is a render of just the Inverted AO pass from our test model.

 

 

After getting the understanding I was looking for, I figured it was time to polish up the model. Using GreyscaleGorilla‘s Topcoat to apply some glossy reflections and a lacquer look to it, and also their HDRI studio kit to add some studio lighting and render with Global Illumination. Looking back, I probably could have just rendered without GI, since the export was a still with a studio background. All we’re seeing is the reflection anyway, but it added some subtle shadowing, reflection pass seen below.

 

 

After that, I’ve become very fond of using Chad Ashely’s workflow for post-depth of field, rather than rendering it in camera from C4D. You can follow that in his tutorial here. The short of it includes rendering a depth pass (not the usual C4D depth pass) and using that to map your DOF in your compositing software of choice. Personally, I’m very comfortable in Adobe After Effects. I’ve started to lean more into it for stills because it is non destructive, and has mostly everything Photoshop and Illustrator could offer, while still being fast and iteration friendly. The largest reason I think is because I am the most familiar with it’s tools and workflow. Speed is key, even if it’s a small test like this.

 

Building off of Chad’s tutorial, I have a good quick-tip to alleviate some guesswork. In the position (soon to be depth) render pass, you need to specify a scale so the camera knows how deep to look when creating your depth pass. Using your shot camera, moving your focus distance to the farthest point back in your scene, in my case, the studio wall, I now have a value for the depth of my scene. I can take that value (found here)

 

 

and calculate the scale that my position pass is looking for using the formula (1/focus distance). After rendering, our depth pass has all the information, but doesn’t look the way our DOF effect (Frischluft Depth of Field) wants to see a depth map. Here is a before and after of that process.

From here, I can do any extra color correction, which in this case was adding a slight vignette and some small curves adjustments to add some contrast and shift some color. Here’s a before and after CC.

 

And then we’re done. It was fun to experiment with some textures, and using the right tools, a small test like this only took a matter of 2 or 3 hours. Most of that includes tinkering and testing values, the fun part. Make your tests quick, goal oriented, and achievable. You’ll do more of them, and have more fun. Honest.

 

 

 

 

 

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