How to highlight parts of my scene - strategy for materials?

Question

I have a scene that looks like this...

_{(source: timevaryinglights.com)}

The renderer is Cycles (probably obvious from the screenshot :) ). Blender 2.78.

I'd like to be able to highlight components, such as the gearbox, in a highlight color such as a slightly emissive orange. This would be for stills and for animation; and for animation it would be cool to be able to fade from current materials to highlighted material over a few frames.

The main question I have relates to materials strategy. Currently, I've got materials such as aluminum, shiny_steel, powder_coat, etc. So this means that if I want to highlight, say, the gearbox, I need all the objects in the gearbox (which are more than one material) to change color, without affecting everything else in the scene that also has the same materials.

At this point, I don't have a handy hierarchy as these meshes were imported more-or-less flat; but I'd be happy to parent all the gearbox parts to an empty called "EMPTY_gearbox", for example. Then maybe the ideal thing would be to add a custom property to the parent that allows me to fade from assigned materials to highlight material, perhaps through a driver (I'm kinda guessing here - I'm not an expert yet... :) )

What's the best strategy for achieving this? How do I get my head around material slots, mix shaders, etc.? I'd rather not have to have several different aluminums, such as aluminum_for_gearbox, aluminum_for_manifold, etc. But if this is what it takes, I can do it, but it seems like a clunky approach.

Thanks!

Dan

Answer 1

I'm answering my own question as none of the answers was quite what I was looking for, but there were gems in there that let me figure it out. Thanks to all those who answered!

My solution:

• I forked local copies of materials, e.g. Aluminum is now Aluminum.Gearbox, Aluminum.Manifold, etc. Thankfully, no component has more than 4 materials, so this was much less painful than I was thinking it might be.

• I created my orange highlight material (some glossy, some diffuse and some emissive), using a node group to make it easy to place in all the materials where I want it.

• I added a mix shader node before the output of these forked materials, and hung the orange color on the other input.

• I added an empty, such as "EMPTY_gearbox_highlighter" with a custom property of "Highlight_Strength", going from 0.000 to 1.000.

• I added simple drivers on the Fac of the mix shaders for all the materials in the gearbox, to be directly controlled by the Highlight_Strength property on the empty.

I'll repeat this for each highlightable component, and then all I need to do is to animate the Highlight_Strength properties on my empties, and it'll fade all the materials in the gearbox (or other component) to orange, which is exactly what I want!

Thanks to all who gave me the stepping stones to get here!

Here's the gearbox unhighlighted:

And here it is highlighted, just by taking that single custom parameter to 1.000:

Answer 2

One way would be to use Object-ID masks in the compositor (see here: How to use an object as a mask?).

You could then (for example) use the RGB curves node and keyframe the fac-value as shown below. Unfortunately, this is not so easy to use. But I'm afraid there is no alternative at the moment...

Answer 3

I would use duplication for this, as it can be keyframed.

Here's a picture run-down.

1. 

2. 

3. 

4. 

5. 

6. 

The three main keys to making this work are as follows:

1. For duplication to work out properly, you have to parent the object created in step #2 above to the Larger (Correct Object). To accomplish this 1st select the smaller object hold Shift then select the larger object. once selection is accomplished, Ctrl+P >> Select Object in the following drop-down menu.

2. There must be enough verts/faces on the main object for this effect to look reasonable. Sub-Divide as necessary.

3. To keyframe the Duplication settings, make sure you are where you want to be in the timeline, select the duplication method that you want (if you want the effect off select None), Then hold your cursor over the selected option, and hit i on your keyboard.

The cons to this are the transition, it's pretty abrupt (If you want control over the abrupt feel of this, I would think about animating the material of the small Duplication object), however highly effective.

Answer 4

You could add another simple object encasing each object you want to highlight and use a mix of transparent and emission. By animating the mixture you can turn on/off the highlighting.

You could use the Is Camera Ray to calculate a weaker emission value towards the camera so that the emission on surrounding objects is more visible.

The highlighting object could be a part of the same mesh as the main object, just with the highlight material assigned to it.

Answer 5

Adding another answer based on some of the comment threads.

This answer has to do with driving the material selection via an Empty object's location.

Here's the pictorial overview:

1. 

2. 

3. 

4. 

Picture 1 above shows the final node setup once everything is in place, so just use that as a final reference.

Here's the run-down:

1. For each mesh object in your scene that you wish to have react to the empties location, I used a Vertex Color slot to just relate the object to the material. I did not use any other Trick, just add the Vertex Color Slot, and give it a unique name. In my example of Picture 2 above, I just use Col, Col.1, & Col.2, to respectively relate to Cube, Cube.001, & Cube.002

2. Next I added these four nodes seen here: Attribute, Math (Set to Greater Than), Emission, Mix Shader

3. You will notice that at the First group of these nodes the first shader input on the Mix Shader is the intended material, the rest is there for a per object basis. The second thing that you will notice, is that the Attribute Node then gets a single name that relates to the Unique Vertex Color Entry that we added previously. The third step to this is to add a driver to the second value slot in the Math node as shown in Picture 3 above. For the Emission Shader Set that to what is desirable to you, and plug that into the second slot of the Mix Shader (The output of this first Mix Shader will be connected to the first input of the next group's Mix Shader).

4. To manipulate the Driver settings, you need to go to the Graph Editor as shown on the right hand side of Picture 4 above., there is a selection menu at the bottom of that screen, which will most likely read F-curve, this needs to be set to Drivers. Next over in the Node Editor, on the Math Node, be sure to select only this node. Make sure the Right side menu is expanded (Hint: with your cursor on the Graph Editor Screen Hit N). Next proceed to to change the driver settings as follows (you will likely have to scroll down on the Right side screen of the Graph editor to see this).

4.a. Change var to have a type of Distance.

4.b. Set the first object to be whatever object corresponds to the Vertex Color Entry (in my case Cube).

4.c. Set the second object to be the Empty Object (in my case Empty).

4.d. In the Expression field set the formula text to:

0.2 if var <= 1.0 else 2.2

Repeat these steps until all of your objects are setup, and keyframe the position of yourt empty.

Here's the result:

Answer 6

I would give all the aluminum for the gearbox a different material. Don't call it aluminum for gearbox. Call it, GearBoxAluminum or something. Eventually you may want to make subtle adjustments for each type of thing because the aluminium in a gear box is going to have different properties than the aluminum in a casing.