When we’re introduced to new terms and techniques it’s helpful to know if this is a brand specific ‘tag’, a concept that belongs specifically to the software or in fact a universal property, used and applied in all similar products. Like ‘NURBS’ (non-uniform rational b-splines), global illumination is a rendering concept defined for three dimensional graphics and lighting.
Global Illumination is any rendering algorithm that simulates the inter-reflection of light between surfaces. That certainly is a mouth full but if you think about, any room you are in or any outdoor environment reflects light from all surfaces. There are many factors, such the light source, how bright the sun is shining if you are outdoors, the reflective properties of the surfaces receiving light but light radiates, and reflective surfaces mirror this light.
Global Illumination, as it’s name implies is a rendering technique that imitates this property of light in our real life environments. Local illumination would have a single light, lighting its direct target. In reality, when a light illuminates a room, there is direct light on the target surface but the remainder of the room also receives reflected, partial light.
Global Illumination in Cinema 4D is one of the advanced render options that provides Cinema with it’s signature ‘larger than life’ appearance. Using special materials for tile, glass, masonry provide a texture and look that is so life like but your render and render settings produce the final product. Using Global Illumination adds the luster and real life luminance and reflections.
Let’s take a look at the advanced render settings and see what they can do for us. Open your render settings choosing the third render icon to adjust the settings, then click on the lower left menu item ‘effect’ to add the ‘Global Illumination’ effect to your render.
In the general tab there are several modes available for still images, animation, QMC (Quasi Monte Carlo), and a sky sampler. Like any special treatment or special effect, it can be helpful to experiment, first with the default settings to get a feel for what this effect is doing, then choose one or two settings to experiment with their single contribution.
There are many tutorials available with scene files but the extra computation to produce the GI effects is very demanding. Your computer processor and memory resources play a large role in determining how long a GI render will take and a more complex scene will take much longer.
Most guides encourage starting with the default settings, possibly reducing some of the accuracy settings.
To get a good preview of what GI looks like, what it can do for your creative scenes, create a simple crystal ball with luminescence and a reflective background. Because you are taking advantage of GI’s algorithm that calculates the true effect of lighting, rays, and refraction it helps to choose a material which adds it’s own depth to your crystal ball surface.
The material applied to your GI object needs to have luminance chosen, it will exhibit more depth if you apply a HDRI texture to your material. If you add your materials ‘transparency’ property, then click on ‘illumination’ at the bottom of your material list properties, the GI Portal option in illumination becomes an option.
There is a delicate blend between the best GI settings, the right materials, and the right material properties which can exploit the GI feature of Cinema. Like nearly all effects and special finishes you are looking for in Cinema 4D, it also takes a lot of practice.
However like nearly all Cinema 4D adventures, it’s fun to practice! I like to begin with simple objects, simple application to get comfortable with a new effect but nearly all the impressive examples I see, (check Kai Peterson, Michael Vance, Greyscale Gorilla), use cloner representations of singular objects with reflective surfaces to really show off, the great Global Illumination effects they achieve.