110,000 triangles in 12.

Bake the detail of a high poly crate into images that a low poly cube can use: a normal map, ambient occlusion and colour. Watch every texel cast its ray, fix what goes wrong, and take the maps to a game engine. Then bake the same crate in Substance 3D Painter.

STAGE

3D Viewport Show

Rays Cage Moving light

Drag to orbit · Wheel zoom

Image Editor

UVs Misses

LMB MMBOrbitWheelZoomHoverRead a texelEscCancel the bakeCtrlZUndo

KEY IDEAS

How a bake works

For every texel of the image, Blender finds the point of the low poly with those UVs and casts a ray towards the high poly. What the ray finds is written into the texel.

Selected to Active: Bake from the selected objects (high poly) to the active one (low poly). Without it, an object bakes itself.
Extrusion: How far out the rays start. It must enclose every detail that sticks out of the low poly.
Cage: A copy of the low poly, inflated along averaged normals, used as the start of the rays. It avoids gaps at hard edges.
Max Ray Distance: How far the rays can travel (0 = no limit). A limit avoids hitting far parts of the model.
Tangent space: The normal map stores directions relative to each UV island: R = right, G = up, B = out. Flat is (0.5, 0.5, 1).
Margin: Extends the islands outwards so filtering and mipmaps don't pick up the empty background.

BACK IN BLENDER

Baking in Blender, step by step

Baking uses the Cycles render engine. The lab shows the same settings, with a simplified crate and a fast ray caster instead of Cycles.

Unwrap the low poly with unique UVs (no overlaps) and put UV seams on its hard edges. Add a material with an Image Texture node pointing to a new image, and keep that node selected: it is the bake target.
Set the render engine to Cycles. In Render Properties › Bake choose the Bake Type.
Select the high poly, then Shift-click the low poly (active). Tick Selected to Active, set Extrusion or a Cage object and a Max Ray Distance.
Press Bake. Save the image (Image › Save): baked images are not saved with the .blend file.
Normal maps: Non-Color + Normal Map node. For Unreal, bake with Swizzle G −Y or flip green on import.
For colour, bake Diffuse with only Color. Keep a Margin of 16 px or more.

BLENDER / SUBSTANCE PAINTER

The same bake, other names

Both programs cast one ray per texel from the low poly to the high poly. What changes is where the settings are and what they are called.

Blender	Substance 3D Painter	Note
Selected to Active	High Definition Meshes	In Painter the high poly is a separate file listed in the Baking window.
Extrusion	Max Frontal Distance	How far above the low poly the rays start.
Max Ray Distance	Max Rear Distance	In Painter it is measured below the low poly surface.
Cage	Average Normals · Use Cage	Averaged ray directions, or a cage mesh made in your 3D program.
Margin	Dilation Width	Extends the islands for filtering and mipmaps.
Bake Type	Mesh maps	Blender bakes one map at a time; Painter bakes every ticked map at once.
Swizzle G −Y	Normal Map Format · Output template	OpenGL or DirectX: in Painter the export template writes the format of each engine.
Separate objects	Match: By Mesh Name	Painter pairs name_low with name_high, so touching pieces don't bake into each other.