Join Donovan Keith for an in-depth discussion in this video Understanding how reflective objects react to light, part of Studio Lighting in CINEMA 4D.
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Diffused objects are generally forgiving when it comes to lighting. But getting your reflective object to look anything other than flat and boring in a studio environment can feel surprisingly difficult. Especially without an understanding of the mechanics of reflection. In this scene I have a series of primitive objects. A polygon, cube, a slightly beveled cube, a cylinder and a sphere. And what I'm going to do is talk about how light hits each one of those and interacts with our camera. If you look at the scene right now, you'll see a rendering of the polygon, which has been colored red and it's reflecting a white soft box off in the distance.
Notice that as I rotate my camera, the light becomes more in focus. And that there are angles from which I can view this polygon where I cannot see that light at all. The diffused component, or that sort of base color, stays constant. The viewing angle has no impact on whether or not a surface is illuminated. That's entirely to do with the angle between the light source and the object itself, and nothing to do with the camera.
However, the specular reflection, or the direct reflection as it's also called, is very much contingent upon how my camera interacts with the normal or the angle of this surface, and where the light is currently placed. Let's go into our four-way view, and just take a look at how this scene is laid out. I'm going to turn on my grid in my right view by going to Filter > Grid, and I'm going to select this polygon so that we can see roughly where it is. It's located at the world origin.
I'm now going to hide my polygon, and reveal my cube. As I rotate my camera around, I see that some sides of my cube are totally in shadow. And the top, although it's sort of dark in terms of its defuse component, can become very white when it's reflecting my light surface. In order to better visualize how my camera angle and my light angle are connected in reflection, I've hacked together a little python script that traces the line between my camera and the surface of my object, and then reflects that line.
I'm going to hide my cube and reveal my polygon to show this. If you look in your side view, you'll now see a blue to red line that is sticking up. Notice that as I change the angle of my camera and release, that angle updates. What's happening is a line or a ray is being shot from my camera to the surface of this polygon, and it's reflecting off. If this ray is totally missing my light, I do not see a reflection.
However, if that reflection ray intersects with my light source, I will see my light. And there are some very steep angles, as we can see, where it will be impossible to see it. Now, a plane here is a fairly simple example. I'm going to go with a slightly more complicated example now, which is the cube. And just update some of these settings. Don't worry about following along with this, as it's not really important. My cube is now shooting out a series of these lines.
And you can see them in the side view. Those lines indicate a place where you could put a light to have it show up in a reflection. And by changing the positioning of my camera, the angle of those lines will also update. It's a little difficult to conceptualize this in the computer. It might be easier just to take out, say, the smart phone that you have with you and try and catch a glimmer of a light in it as you move it around in your hand. That'll give you a much quicker intuitive sense of how these reflections are playing off our surface.
I'm now going to switch over from my plain cube here to a cylinder. These lines are now shooting out in almost all directions. This indicates to me that a cylinder does a really good job of reflecting what's around it. Remarkably, there are no lines directed straight at my light right now. In order to capture that I need to adjust the angle of my camera until some of them are pointed at the surface. And if I was to hide my special rig right here we would now see a reflection of our light in the edge of our cylinder.
A sphere is another interesting example. A sphere reflects light in pretty much every direction, including what's behind it. It's a little hard to believe, but if we were to rotate our light, and then hide this rig. What we would see is a reflection of our light source on the edge here. Even though the light source is more or less behind our sphere. To grossly oversimplify the point of this video, good looking reflections need round edges and an interesting environment that will reflect from the current viewing angle.
If your camera and your lights don't align, you won't get a good reflection.
- Describing light
- Understanding the difference between real light and light in CINEMA 4D
- Using lighting direction to reveal form
- Adjusting light hardness
- Top lighting a subject
- Rendering reflective objects
- Shooting glass
- Separating objects from the background
- Hinting at a world outside the frame with gobos