Bake Vertex Color

Description

Vertex Colors (Vertex Colours) are an alternative way to ‘paint’ a mesh. By default however, they are visible in Solid display mode only while Vertex Paint is active. To see them in Material Preview, Rendered display, or to bake vertex colours painted to a mesh as a distinct image texture, materials need to be set up, or modified, to include a Color Attribute node.

Duration: total c. 10 mins hr (00:10:00).
Info: 1080p.
Suitability: Beginner+.
Source: n/a.
Product ID: n/a.

Design note: additional considerations when baking vertex colours in Blender;

Vertex Colour Visibility

By default vertex colours are only visible when the viewport is set to display meshes in Solid mode [1]. In other words, toggling into Vertex Paint while Material Preview or Rendered display is active, shows no colouring. Similarly, because default painting behaviour occurs in Solid mode, more advanced properties typically associated with a given material, will be ignored in favour of basic options accessible under Viewport Shading.

Vertex painting is only visible when the viewports display mode is set to Solid [1] which ordinarily renders objects in a grey ‘clay’ like material.

Vertex Painting & UVs

As a consequence of how vertex painting works and what vertex colour is actually doing, objects do not need in of themselves, to be UV unwrapped or mapped, no UVMap datablock [2] is necessary, because ‘mapping’, where colour is painted or appears, is expressly determined by mesh structure. This means UVs [3] are not explicitly needed for an object to be painted, or appear ‘textured’. Similarly, this also means material assignments are not strictly needed either, the data that describes colour is stored as an attribute of the Vertex element.

Vertex painting doesn’t require objects be UV unwrapped or UV mapped [2], no UVs are needed [3] because colour is a ‘value’ property associated with individual vertices.

Material Node Tree

To bake vertex colours to an image they need to be visible to the Scene (display modes) and Bake system. This means a material must be assigned to the vertex painted mesh and tweaked to facilitate this. To do this, select the vertex painted mesh and assign a material (existing or now). In Shading Workspace, with mesh still selected to expose the Node tree, drop in a Color Attribute node from the Input submenu of Add – Add » Input » Color Attribute. The ‘attribute’ value for this should default to the existing entry, initially Attribute (can be renamed) [4], in the Color Attribute datablock [5]. If not click the input field and assign. This node then effectively replaces what would ordinarily be the Image Texture node assigned to Base Color of Principled BSDF.

Important: as of Blender 3.0 the vertex colour datablock shown in Color Attributes (formally Vertex Colors) is named “Attribute” not “Col“. This can be changed where needed by double-clicking the entry and typing a new name – material node assignments may need to be manually updated to correctly reference the re-named datablock.

Aside: for Texture Baking, vertex colours are typically painted to the high-resolution mesh, the object from which colour and surface property data is usually baked – the material won’t specifically need to be any more complex in-of-itself other than enabling the display of vertex colours, i.e. using the modified material and/or switching to Material Preview or Rendered display mode – vertex colour doesn’t appear in Solid mode regardless.

Adding a Color Attribute node [4], which should default to the active datablock in Color Attributes [5], once connected to Principled BSDF, will then display the vertex colouring painted to the mesh.

Vertex Color Bake

Once vertex colour is visible to display and render, Texture Bake can be used in the normal way to bake, in this instance, the Diffuse image map. Switching to Cycles engine, expand Bake options and set Bake Type to Diffuse – if colour only is to be captured, i.e. no shadows or shading, disable Direct and Indirect light influence under Contributions.

Aside: although vertex colours are being baked in this instance, subject to the exact properties associated with the material – Roughness, Metallic etc., the presence of vertex colours won’t interfere with baking or rendering other map types, e.g. normal maps.

To capture, or bake down, vertex color it needs to be Baked as a Diffuse map. To ensure just colour is captured disable Direct and Indirect [6] light influences over the render then Bake as is normally done when using Bake.

Timestamps

Times are approximate;
– 00:00 : Node Tree
– 04:00 : Vertex Bake