Force background image to render unaffected by lighting
Posted: Sat Sep 19, 2009 9:35 pm
Para ver la versión en Español, presione aquí.
Some users don't want to add a background in post-processing but prefer to place it as a plane inside SketchUp. Also, you might want to add images to TVs and computer screens. In all these cases, you might want the inserted image to render exactly as it is, without being affected by the sun/sky/lights in your scene. Here's how.
The following setting works perfectly for Exposure = 1.0, Gamma = 1.0:
1 - Explode your image so it becomes a texture applied on a plane.
2 - In the Twilight material editor, choose Templates > Light Emitter, any of them
3 - Set the Power (W/m2) to 150.
4 - Next to the light bulb, Change Emitter > Normal to Emitter > Fake.
5 - Unmark the "Cast shadow" checkbox.
Your material settings should now look like this:
If you're using a different Exposure value, use this simple formula to calculate the power for your fake emitters:
Power for your fake emitter = 150/exposure²
Examples:
For an exposure value of 0.5, you must set your fake emitters to 150/(0.5)² = 600.
For an exposure value of 1.2, you must set your fake emitters to 150/(1.2)² = 104.167
For an exposure value of 2, you must set your fake emitters to 150/(2)² = 37.5
In all cases, you need to keep a gamma of 1.0 if you want your images to render unaltered.
NOTE: Fake emitters only exist in Presets Easy 01-08. With Easy 09-11 they become real emitters, thus contributing light to your scene.
Feel free to translate this information to other languages and post it to the respective international forum.
Some users don't want to add a background in post-processing but prefer to place it as a plane inside SketchUp. Also, you might want to add images to TVs and computer screens. In all these cases, you might want the inserted image to render exactly as it is, without being affected by the sun/sky/lights in your scene. Here's how.
The following setting works perfectly for Exposure = 1.0, Gamma = 1.0:
1 - Explode your image so it becomes a texture applied on a plane.
2 - In the Twilight material editor, choose Templates > Light Emitter, any of them
3 - Set the Power (W/m2) to 150.
4 - Next to the light bulb, Change Emitter > Normal to Emitter > Fake.
5 - Unmark the "Cast shadow" checkbox.
Your material settings should now look like this:
- fake-emitter-150-noshadow.jpg (82.77 KiB) Viewed 15181 times
Power for your fake emitter = 150/exposure²
Examples:
For an exposure value of 0.5, you must set your fake emitters to 150/(0.5)² = 600.
For an exposure value of 1.2, you must set your fake emitters to 150/(1.2)² = 104.167
For an exposure value of 2, you must set your fake emitters to 150/(2)² = 37.5
In all cases, you need to keep a gamma of 1.0 if you want your images to render unaltered.
NOTE: Fake emitters only exist in Presets Easy 01-08. With Easy 09-11 they become real emitters, thus contributing light to your scene.
Feel free to translate this information to other languages and post it to the respective international forum.
