ID Pass in Blender

How to Generate an ID Map in Blender Easily and Accurately

Since I started working in the 3D world, many clients accustomed to renders in 3ds Max with V-Ray or Corona would request, along with the final images, a "ID pass in Blender(also known as "Render ID passor "the wire."

In other engines, it is usually a straightforward process, but inBlenderhas always been more complicated.

Initial methods: random colors in Workbench

The initial solution involved creating a material that assigned random colors to each object, applying it as "material overrideand render inWorkbenchThe result was an image of distinct colors, although often too similar, with only one color per object.

The arrival of Cryptomatte in the compositor

Later, with the inclusion of the nodeCryptomatte, the flow improved:

• It allowed the generation of ID maps by object, material, or asset.
• It was no longer necessary to render in Workbench.
• But it still required manually adjusting colors that were repeated in adjacent objects.

For years, this was the way of working until I found something better.

Discovering the Render Tools addon

A few months ago, while browsing throughSuperhiveIn search of addons that optimize my workflow, I discoveredRender ToolsThis addon automatically assigns a color ofviewport materialto each object and, with a single click, generates theRender ID passin Workbench without changing the rendering engine.

The major issue: transparent materials

All methods failed at the same point:the transparent glass and materialsWhen a transparent object was in front of the camera, its material obscured everything behind it, which poses a challenge in projects involving glass, such as partitions or windows.

Adjusting the Viewport Shading

The key lies in theViewport Shading.

• If you leave it at "Lighting → StudioyColor → Aleatorio, the addon does not apply its colors and the ID pass appears incorrect.

The solution: use 'Color → Material'

If you change the "Viewport ShadingaMaterial, Blender begins to display the colors configured in theViewport Displayof each material.

• You can configure them manually.
• Or let the Render Tools addon assign them automatically.

Controlling Transparency with Alpha

The final key is to modify theAlphaof those colors.

• In glass materials, it is sufficient to reduce the Alpha value in theViewport Display.
• Thus, the transparent material no longer obscures the objects behind it.

Conclusion

Generate aID map in Blenderit is no longer a headache.

• The initial methods (Workbench and Cryptomatte) are effective, but they are limited.
• With the addonRender Toolsand the correct adjustment ofViewport Shading in Material modea clean ID pass is achieved, even with transparent materials.

A simple trick that saves time and enhances the quality of the renders delivered to clients.