How to fix black rectangles from Area lights in Redshift

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When rendering interior scenes with Redshift in Archicad, ceiling lights may appear as black rectangles instead of evenly glowing panels. This issue is common in interiors with ceiling grids and diffused lighting panels and can make the visualization look artificial and distracting. This article describes how to hide the Area light object in the render and use a glowing surface instead, so the ceiling panels appear naturally lit while still contributing to the overall illumination.

What is a Redshift?

Redshift is a GPU-accelerated rendering engine available in Archicad with a Full or Commercial license and an active Graphisoft Forward subscription. It is integrated through the Cineware by Maxon rendering engine, providing faster and more realistic renders directly from Archicad. Learn more about Redshift in this article.

Issue description

When rendering interiors with Redshift, Area lights can sometimes appear as black rectangles in the final image. This happens when their visibility settings are not configured correctly, resulting in unrealistic and distracting artifacts in the render.

Solution

Before diving into the steps, let’s clarify the scene setup and the role of the Area light. Area Light is a type of light source used to simulate realistic lighting in interior renders. They act as light emitters and are often used to create soft, diffused lighting. They won’t visibly appear in the final render unless configured improperly.

Area light set-up

1. Adjust Area Light Settings: 

• Select the Lamp Tool, then open the Object Settings 
• Navigate to the Area Light settings and turn off ‘Visibility in Render’. This ensures the area light will not appear as a black rectangle. 

Area light setting

2. Create a New Surface with Luminance: 

• Go to Surfaces in the Attributes menu and create a new surface
• In Engine settings, choose “Cineware and Redshift by Maxon” 
• Enable the Glow and Luminance in Cineware Settings 
• Adjust the intensity to make the surface emit light effectively 

New surface with luminance

3. Apply the Surface to the Light Object: 

• Assign the newly created luminous surface to your light object in the Lamp Selection Settings. Apply it to the surface that emits light. 

Override surface in Lamp Setting

Outcome

This setup will make the light appear visible in your scene, eliminating the black areas while providing accurate illumination.

Final render with realistic lighting

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These techniques were originally shared by Community member @derekjackson. If you’d like to explore the original discussion, click here to read the full thread!

This article is part of the ‘Tip of the Month’ series on Graphisoft Insights, highlighting valuable community-driven solutions for modeling challenges. Try these methods in your next project and experience the difference in model quality and efficiency.

Redshift is a GPU-accelerated rendering engine available in Archicad with a Full or Commercial license and an active Graphisoft Forward subscription. It is integrated through the Cineware by Maxon rendering engine, providing faster and more realistic renders directly from Archicad. You can learn more in the Redshift for Archicad overview on Graphisoft’s website.