To make light pass through an object in Blender, you need to prevent that object from casting shadows. By disabling the shadow casting property for the object, light sources can shine through it as if it were transparent to their shadows.
This method works in both Blender's Cycles and EEVEE rendering engines.
Steps to Allow Light to Pass Through an Object
Based on the provided reference, the core action is to disable the shadow casting of the object that is blocking the light.
Here's how you typically do it:
- Select the Object: In your 3D viewport, select the specific object that you want light to pass through (the one currently casting a shadow).
- Navigate to Object Properties: Go to the Object Properties tab in the Properties editor (usually located on the right side of the Blender interface).
- Find Visibility Settings: Within the Object Properties, look for a section related to visibility or ray visibility.
- Disable Shadow: Under the visibility settings, you will find options for which types of rays interact with the object. Deselect the "Shadow" option.
As shown in the reference, when you "deselect the shadow... the shadow disappeared. And the light from this source can pass through the cube." This confirms that disabling the shadow property is the key action.
Why This Works
Blender uses ray tracing (or similar techniques in EEVEE) to determine how light interacts with objects. When an object casts a shadow, it means it blocks light rays traveling towards other surfaces. By disabling the "Shadow" option for an object, you are essentially telling Blender's rendering engine to ignore that object when calculating shadows, allowing light rays to continue traveling through it.
This doesn't make the object visually transparent itself (unless you change its material properties), but it makes it invisible to shadow rays.
This technique is useful for various effects, such as creating volumetric lighting effects coming from within an object, faking light passing through windows without complex glass shaders, or simplifying scenes where certain objects shouldn't block light.
