A Guide to Using Passes and Cryptomatte for Architectural Rendering in Blender

Blender’s current online manual defines render passes as separate outputs of intermediate images and data from a scene. In architectural visualization, these layers help you edit a piece of furniture, a surface material, a lighting effect, or depth information independently of the main image. This guide adapts the passes, Cryptomatte masks, and Compositor connections described in the manual to interior and architectural rendering workflows. The source pages are from Blender’s “latest” manual and do not specify a particular Blender version number.

1. Choose the right pass for the task

Before enabling passes, decide which parts you may need to change later. Cryptomatte is a good starting point if you only need to select objects. If you need to work with depth effects, lighting components, or custom shader data, consider the relevant pass options. Also keep in mind that not every additional pass is available in every render engine.

Pass options are located under Properties › View Layer › Passes. In Cycles, you can use Light Groups, Denoising Data, lighting components, and options such as Object Index and Material Index. EEVEE has a different pass list; for example, it includes Shadow, Transparent, and Ambient Occlusion options. The manual states that EEVEE supports up to 16 Color and 16 Value AOVs. Choose your settings accordingly, based on the render engine in use and your compositing needs.

2. Create an object or material mask with Cryptomatte

1. Under Properties › View Layer › Passes, enable Object, Material, or Asset under Cryptomatte. For an interior render, use Object to isolate a single chair or light fixture, or Material to select elements that use the same surface definition. If a group consists of objects linked to a shared parent, consider the Asset option.

2. Render the scene. Cryptomatte works through render passes; an image rendered without the pass enabled will not contain Cryptomatte data generated by Blender. If the image comes from other supported software, the node can also use a Cryptomatte image in a multilayer OpenEXR as its source.

3. Add a Cryptomatte node in the Compositor. In the Source field, choose Render to use passes from a Blender render, or Image to use a multilayer OpenEXR. In the Cryptomatte Layer field, specify the image layer to use; this is usually a combination of the View Layer and the Object, Material, or Asset type.

4. To make selection easier, connect the Image output of the Render Layers node to the Image input of a Viewer node, and make sure the Viewer background is visible. Use the selection button on the Cryptomatte node to click an object in the image and add it to the mask; repeat for other elements. Selections can also be stored in the Matte ID field as comma-separated names.

5. Use the Cryptomatte node’s Matte output to get a grayscale mask of the selected objects. If you need an image that keeps the selected objects visible and makes everything else transparent, use the Image output. Connect the mask to color correction or compositing operations to edit only the target area.

3. Use passes in an architectural visualization workflow

An interior shot requires different kinds of data for material color, light distribution, and object selection. Diffuse Color contains the color of surfaces, while Diffuse Light contains the intensity and color of the light reaching a surface. In Cycles, Direct and Indirect lighting components can also be output as separate passes. This distinction is useful for teams that want to handle lighting effects and material appearance separately during compositing. Light Groups produce limited Combined passes illuminated by specific lights. These are not Cryptomatte masks; the passes can be combined in the Compositor to adjust the lights’ colors and intensities without rendering again.

For depth and atmospheric adjustments, consider Depth or Mist. Depth gives the distance to the nearest visible surface from the camera; the manual says this pass can be used with the Defocus node to create a fake depth-of-field effect. However, Depth can be noisy if the render includes depth of field or motion blur; the manual recommends the Mist pass for a cleaner image. Mist maps distance to a range of 0.0–1.0 and can be used to fade distant objects.

Denoising Data includes auxiliary data such as albedo, specular albedo, normal, roughness, and depth, in addition to the noisy image. This can provide more information to the Denoise node in the Compositor, but increases memory use and render time. Enable this data only when denoising in the Compositor is required. In EEVEE, depth of field and motion blur are not rendered in passes other than Combined; the manual notes that these effects can be simulated with the Defocus and Vector Blur nodes in the Compositor.

Shader AOVs can be used to pass custom data from materials to the Compositor. Create a pass in the Shader AOV panel, write data to that pass using an AOV Output node in the material, and use the corresponding output of the Render Layers node in the Compositor. Choose the Color data type for color, normal, or another vector, and Value for a single number. This method is intended for workflows that need custom data not available in the standard passes during compositing.

Common mistakes

• Rendering without enabling the Cryptomatte pass leaves out the steps needed to create masks from Blender’s own Cryptomatte data.

• Using the Depth pass in an image with depth of field or motion blur can produce noisy results; consider Mist instead.

• Enabling Denoising Data unnecessarily increases memory use and render time.

• In EEVEE, transparent surfaces set to Blended are not included in passes other than Combined and Transparent. According to the manual, Dithered can be used as an alternative; the Transparent pass supports grayscale opacity only.

• Remember that the Object Index, Material Index, Depth, and Position passes are not anti-aliased. Check mask quality around fine edges.

For architecture and interior design teams, the practical benefit is the ability to edit selected objects or lighting components in compositing instead of recreating the entire image for last-minute changes. Cryptomatte creates object and material masks, while Cycles Light Groups provide Combined passes for separate light groups; the two features should not be confused. The trade-off is that more passes can mean more data; the manual explicitly notes the cost of denoising data. Before delivery, test which passes are supported by the render engine in use and check the limitations of transparent materials.