Working with visible or volumetric light
Video: Working with visible or volumetric lightHave you ever been to a theater and looked up at a spotlight that was shining down on an actor on the stage and been able to see that cone of light coming out of the light source? Normally, you are not able to see light photons, but in a spotlight like that, you're actually not seeing the light itself, but you're seeing the light bouncing off of little dust particles and moisture and smoke and things like that that are in the air. That visible light is another component that the programmers have given us to work with. I've got a very simple scene opened here.
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CINEMA 4D Essentials with Rob Garrott is a graduated introduction to this complex 3D modeling, rendering, and animation program, which breaks down into installments that can be completed within 2 hours. This course shows how to lend 3D objects color, transparency, and life with materials, textures, and lights. Author Rob Garrott explains how to create a variety of surface textures, from smooth and reflective to bumpy and flat, and how to add dramatic depth and shadows to your scenes with the different light types in CINEMA 4D. The final chapter discusses texturing in 3D with the BodyPaint module, which can also help hide UV seams.
- Understanding material channels
- Applying materials via projection
- Limiting materials with selection tags
- Texturing type
- Using Falloff to limit the effects of lights
- Working with visible or volumetric light
- Painting on objects and textures with brushes in BodyPaint
- Hiding seams with projection painting
Working with visible or volumetric light
Have you ever been to a theater and looked up at a spotlight that was shining down on an actor on the stage and been able to see that cone of light coming out of the light source? Normally, you are not able to see light photons, but in a spotlight like that, you're actually not seeing the light itself, but you're seeing the light bouncing off of little dust particles and moisture and smoke and things like that that are in the air. That visible light is another component that the programmers have given us to work with. I've got a very simple scene opened here.
Before we look at this specific example though, let's take a look at some of the settings. I'm going to make a new document by hitting Command+N or Ctrl+N, and let's add a spot light to the scene. I'll click on the Light object and go to Spot Light. Now on the Light, under the General properties, I'm going to click and hold on Visible Light. There are four options here: None, which is the default and then Visible; Volumetric; and Inverse Volumetric. Visible Light is the least intensive of the three options, and if I add that, you can see that my cone has changed. Let's render. Command+R or Ctrl+R.
I can now see that cone of light. Let's undo for a second and render again. Command+R or Ctrl+R. You can see that I don't see anything. Now to keep myself from having to hit Command+R or Ctrl+R again, let's bring up the Interactive Render Region, which is Option+R or Alt+R. There's a Quality slider on the right-hand side here, so let's drag that all the way up to the top so we have full quality on this preview render. Now let's go back to the Light source and change the Visible Light back to Visible from None. Now we can see our light source, and every time we make a change it will get updated automatically here.
Now that we have the visible light active, let's go to the Visible Light options. Under the Visibility options, we've got Falloff, and Falloff affects the shape of the cone of visible light. If I uncheck Use Edge Falloff, for example, you can see that now the cone of light no longer diminishes with intensity towards the edges of the cone, and it's very much more conically shaped, and you can see that it's much more defined. And if we turn off that Falloff, you can see that the cone of light is really specifically defined. Now, what's causing the end of this cone? The end of the cone is being caused by the Outer Distance, and the Outer Distance is this little guy right here.
And as we move that Outer Distance out, you can see that our cone extends outward. Let's turn the Falloff back on for both of those guys, and now we can see that we have a softer cone. When we activated the Falloff again, we now have access to the Inner Distance, and the Inner Distance controls the density on the inside of the cone. If we make the Inner Distance closer in value to the Outer Distance, what's going to happen is that the Falloff region for our cone is going to get shorter and shorter. Another important option to look at is the Gradient. The Gradient object allows us to control the color of this cone of light over the length of the light source.
So if we turn on the gradient, we now have access to the color. And it defaults to a single color, and we can change those. So let's click on one of these knots here, and when we double-click on that, it brings up the color picker. So I'll change it to red and hit OK. You can see that that changed the start of the light source. Now my Inner Distance is set really high, which is what's causing it to be red all the way up to this point. So let's bring that back down to zero. And now you can see that we have a much longer gradient. We can take that Midpoint slider and adjust it so that we have a little bit more pink light source, and then we can go back here.
Now if we click on this last knot, we can adjust it, make it a little more pink, and you can see that we have a little bit more realistic representation of that red cone of light. I want to be very careful here. This Gradient color that I'm adjusting does not affect the color of the light; it only affects the color of the visible light. So to illustrate that, I'm going to add a sphere to the scene and then drag that sphere on the Z axis and so that it's shining. You can see that even though have a red cone of light, the light hitting our sphere is still white. If I go back to the Light properties and go to the General tab, if I change the color of the light source-- watch, I'll make it more of a fuchsia-- you can see that we have a red cone and a fuchsia light source.
Let's bring it to red as well, and now we can see we have got a red cone and red light. So those are pretty much the settings for the Visible Light. In order to see Volumetric, let's take a look at that scene we had opened earlier. So I'll go to the Window menu and go back to the Visible-Volumetric-START. And what I have here is a simple grid of cubes, and you can see that it's just a grid. At the very center of the grid, it's opened at the center of the world. I'm going to add an omni light to the scene. Before I do, let's navigate around so that we can see the cube from a distance. And let's add an omni light. I'll click once on the Light object and that comes in the scene.
Let's bring up the Interactive Render Region, Option+R or Alt+R, and let's change the size of that so that it's encompassing our entire frame here. Let's bring it out on the sides as well. There we go. Now we'll crank the Quality slider up to the top. So, you can see that our cube is looking pretty interesting, but we want to activate Volumetric Light. You can see that's going to have a much more interesting effect. So, we go to the Visible Light pulldown under the General properties of the Light source, and we're going to add Volumetric. So when we add Volumetric it's going to redraw the scene. And you can see now we start to see these little edge rays out here.
Now, these orange dots that you're seeing represent the outer region of the extent of that volumetric light. And if I hit Option+R or Alt+R on the keyboard to get rid of the Interactive Render Region, you'll see that we now can see the rings that are surrounding our light. Let's drag those outward to get a more strong effect. Remember, this represents a Falloff region, so it's 100% at the center and 0% out here, with a very strong falloff and intensity. Let's hit Option+R or Alt+R. That region is going to come back at the same size and fill our screen.
And you can see now we have a much more strong effect on those edge rays. The difference between Volumetric and Visible is that Visible light does not interact with the objects. Volumetric light does interact with the objects, and what it does is it creates striations, or visible lines, in the visible light based on the edges of the objects that it's interacting with. Now, I don't normally use Visible or Volumetric light in my CINEMA 4D files. I wanted to show it to you here today because there may come a time where you'll need it.
Let's take a look now at the Visibility option again, and you can see that we've got our same settings here as before, so nothing really changed between the Visible or Volumetric settings. Now let's take a look at Inverse Volumetric. So I'm going to go back to the General properties and go to the Volumetric pulldown and select Inverse Volumetric. And the thing I want you to pay attention to are the edge rays that are extending out from our cube. Now what's happening is we're getting the inverse of those edge rays. Before, the edge rays were being occluded by the cubes; now we're getting the opposite of that.
The cubes are being occluded by the edge rays, and you can see that it's not nearly as distinct an effect, but it gives us this really interesting sort of interaction with the cubes that has a much more glowy feel to it. But there's a great plug-in called Shine for After Effects that creates a Volumetric light effect that you can use in your projects. It renders much faster than CINEMA 4D's Volumetric Light effect, and it has the added advantage of being able to customize it right in After Effects without having to come back and re-render your entire scene. There are some disadvantages to it, in that you don't have quite as much flexibility on interacting with the objects as you would within CINEMA 4D, but you don't have to re-render a scene each time you want to make a change.
The Visible and Volumetric Light settings in CINEMA 4D can give you some really interesting effects, but remember, you're not limited to doing those right here in CINEMA 4D. You can choose to do them in post in other applications like After Effects or Photoshop.
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