Size does matter
See images below and you will find the size of the Rectangular Light has an affect its intensity.
Shadow changes according to the size.
Larger Rectangular Light spreads out to a larger area, so the shadow is not as clear as you will get from a smaller Rectangular Light.Compare images below and you will see the differences between two different light sizes. The one on the left is rendered with smaller light.
If you want to have a stronger shadow, we do not recommend you set the intensity way high and make the light size really small. It's better to use a different light type in V-Ray. Please see dialogue box of how to create a Point Light later.
Impacts on reflective objects due to Visible and Invisible Rectangular Light
There is an Invisible option in Rectangular Light. It allows the light visible or invisible from the render image.See images below. The one on the left has the Invisible option unchecked so the light appeared in the image.
When apply a reflective material to the object, the light will also being reflected on the object. The image on the right has the Invisible option checked. Thus, you don't see the light in the image or on the object with reflective material applied to it.
The default setting for Rectangular Light has the Invisible option unchecked. If you see any unusual dark shadow in your rendered image, please check if your camera is blocked by the Rectangular Light in the scene.
Double Sided Option
You can tell the direction of the light from the SketchUp face orientation of the Rectangular Light. Reverse the face and you can change the direction of the light.The Double Sided option can turn the light direction from one side to both side of the light. Just like to create two lights with opposite directions. Move the light away from the floor or wall to avoid any black out area.
Double Sided option usually used when renders a big interior scene. It helps to lit up the space without using too many lights. Normally we don't use it when render a product scene.
There will be more discussion about lighting and environment lighting later on.
The default has the Double Sided option unchecked. Of course, if you check and Invisible option, you will not see the light in those three images on the next page.
1. Light direction towards the left side.
2. Light direction towards the right side.
3. Double sided option checked.
Pay attention to the size, location and intensity factors of Rectangular Light because they will affect the brightness and shadow clarity of your final result.
If the light is placed too far away and the subject is not bright enough, you can either increase the intensity or size of the light. On the other hand, you can lower the intensity or reduce the size of the light if you place the light too close or too bright. You will need to keep adjusting the size, location and the intensity of the rectangular light in order to get good lighting result.
