Alternative to Cinema 4D Global Illumination

In the first part of this tutorial, we saw that we can get excellent results from Cinema 4D's Global Illumination render in as little as half the time by tweaking the rendering parameters. In the second part of this tutorial, I am going show you an alternative to using Global Illumination that will also yield excellent results in even less time.

For this tutorial you are going to need a special plug-in. Go to and you'll find a plugin called LUMEN by Chris from LUMEN comes in two versions, LUMEN and LUMEN Lite. Have a look at the sample videos for LUMEN and I think you will agree that its a fantastic deal for $35. However, this tutorial only makes use of the LUMEN Lite plugin, which is free (you'll find it on the bottom of the LUMEN page). Download and install the LUMEN plugin in your Cinema 4D Plugins Folder and restart the program.

Once you have installed the plugin, under the Plugins menu in Cinema 4D you'll find a new item called LUMEN Lite. Choose this item, and a new LUMEN Lite object is added to your scene heirarchy. You will need to add two objects as children to the LUMEN Lite object - geometry to attach lights to, and a light object that will be replicated on all of the geometry object's points. In the full version of LUMEN you can choose points or polygons, but in the Lite version lights are only attached to points. See the image at the right to see how the hierarchy is arranged correctly.

We are going to use a Sphere as the geometry object. For now, adjust its settings to match the diagram at right. I used Icosahedron because the points of that sphere type are evenly distributed across the object. Normal spheres have points concentrated at the poles.

lumen plugin setup lumen plugin sphere settings

Set Up the Lights
Add an Omni light to the scene and group it under the LUMEN Light plugin as shown above. LUMEN will take this light and replicate it all over the points of the Sphere object. This will result in far too much light being cast on our object, so we are going to use a feature of LUMEN to adjust the light properies using a texture.

Here I have set up a gradient and applied that gradient to the sphere. In the LUMEN plugin in, I have set the Set Light Color property to ON, and dragged the gradient texture tag into the Texture Tag box. The gradient's brightess is set very low in the material editor because we have many lights, and each light does not need to be very bright to properly illuminate the scene. I have also adjusted LUMEN's Keep Above parameter so that lights below the floorline will be omitted from the scene.

Lumen will use the gradient properties to adjust the color and brightness of the light according to the color and brightness of the gradient at each point on the sphere. You can use anything here for a texture - a simple gradient as in this example, or a picture of a room or scene, or any other texture.

lumen light texture setup

Missing Shadows
Here are the results of our simple setup — the basic shading looks right, but the shadows are missing. The render time is only 24sec.

Lets see what can be done to add shadows to the scene.

lumen results no shadows

Raytraced Shadows
Go into the General tab of the Light settings for the light object in the LUMEN hierarchy, and change the Shadow type from NONE to Raytrace (Hard).

Looking at the results here (which took 11min 27sec) we can see that we are getting some very nice soft, pooling shadows on the body of the object. The shadows fall apart under the object however, releaving their nature as multiple shadows cast by multiple point sources. Well, there is a fix for that, and the fix is called Shadow Maps .

Before we enable Shadow Maps, we need to change our light type from Omni to Spotlight. The reason is that Shadow Maps have a fixed resolution - set in the Shadow tab of the Light object properties. When the light type is set to omni, the shadow map resolution is shared every direction the omni light shines — most of it not in the direction of our object. By changing the light type to spotlight, all of the Shadow Map resolution is restricted to the direction the light is shining — on our object.

lumen ray trace shadows

Shadow Maps
When you change the light type from Omni to Spotlight, there is one more setting in LUMEN that you have to adjust. Under LUMEN's Alignment tab, change the Target Type from None to Object. Then drag and drop your object (or a target null object) into Target Object parameter. You'll see in the editor windows that all of the spotlights are now shining on your object.

Under the Shadow tab of the Light object, change the Shadow type to Shadow Map. Set the resolution to be 1000x1000. Set the Sample Radius to 1, and the Absolute Bias to .5m. Render the scene, and lets look at the result.

The immediately noticable thing is that the light is more concentrated on our object — the background has receeded into inky blackness. The other noticable thing is that the results are remarkably similar to the ray-traced shadows, but the rendering time has dropped to 1min 53sec. Clearly we are on the right track.

lumen ray trace shadows

More Lights
With a brief rendering time of only 2minutes, we can afford to increase the number of lights to smooth out the shadows. With LUMEN this is quite easily accomplished. Click on the Sphere object, and change its Segments from 24 to 48. You'll see the number of spotlights in the editor window jump up in number.

Because the number of lights has increased, we need to decrease the brightness that each light has. Click on the Light object in the LUMEN hierarchy, and under the General tab, reduce its brightness from 100 to 20. Lets widen the area the light is shining on too — go to the Detail tab, and change the inner angle to 30, and the outter angle to 60. This will have two effects: it will soften the shadow maps a bit by spreading them over a wider area, and it will brighten up the scene some. Render, and lets look at the result.

We have very smooth shadows now, nearly as smooth as Global Illlumination. If we had textures on the floor and object, chances are the remaining artifacts would be invisible. Alternatively, increasing the shadow map Sample Radius can help smooth out the remaining artifacts on the floor. Be wary though... shadow maps can have a tendency to leave dark halos around detailed areas — an effect that is creeping into the sample image here.

The final render time for this image is only 13min 51sec, nearly half that for the Global Illumination Render. Roll over the image to compare the two techniques.

lumen and radiosity compared
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