Depth map vs displacement map: the difference that changes the export

A depth map stores one distance value per pixel from the camera or a reference plane. Near and far are defined relative to the view. It is useful for compositing, parallax, atmosphere, masks, fog, and depth of field. It is not automatically a displacement map, because displacement depends on the surface normal and the mesh topology.

A depth map can be remapped into a displacement-like field for a relief, but the interpretation changes. If the renderer expects displacement along a normal and receives a camera-distance field, the result can stretch on curved surfaces or move in the wrong direction. Record the reference plane as well; a depth map without it is only relative.

A displacement map tells a renderer how far to move each shading point along the surface normal. The values are usually relative to the mesh and the displacement scale. A flat plane and a sphere can use the same texture and produce different geometry because their normals differ.

This is why a displacement map needs a sufficiently dense mesh or a tessellation step. A low-poly surface cannot express fine displacement no matter how detailed the texture is. It also needs a consistent UV layout and a known mid-level, so the surface does not inflate or collapse.

Most displacement workflows define a mid-level, often 0.5. Values above the mid-level push outward; values below pull inward. If the mid-level is wrong, the whole surface inflates or sinks before any detail appears. Set the mid-level explicitly, then check the silhouette of a simple test object before applying the map to a complex mesh.

A grayscale image has no units and no direction until you assign them. In a depth context, white might mean near. In a displacement context, white might mean outward. In a height-map context, white might mean high. The file is identical; the shader and the workflow are not.

Before exporting, write down the convention. Is the value normalized to 0-1 or 0-255? Is it linear or sRGB? Is white near or far? Is the displacement centered at 0.5 or at zero? A map that is correct for one pipeline can be inverted in another.

Use a depth map when the goal is to describe scene distance: compositing, relighting, atmospheric effects, masks, or a depth pass for a camera move. Use a displacement map when the goal is to move an existing surface: adding relief to a plane, detailing a sculpt, or driving a tessellated mesh. Use a height map when a CAM or 3D-print workflow expects elevation from a base plane.

For a CNC relief or a printable plaque, the height-field interpretation is usually the right one. For a VFX shot, the depth interpretation is usually the right one. The same source image can produce both, but the export and the documentation must say which one you produced.

A useful test is a plane and a sphere with the same map. On the plane, displacement moves along one direction; on the sphere, it moves along many. If the sphere shows stretching or a seam, the UV layout or the tangent basis is the problem, not the grayscale. Fix the mesh or the mapping before adjusting the texture.

The workbench produces a depth estimate and a height field for relief. It does not silently call the result a displacement map. The free 8-bit PNG is labelled as a preview, the compatibility 16-bit container is labelled as preview-derived, and the production bundle records the direction and normalization in its manifest.

If you need a displacement map for a specific renderer, convert the height field in that renderer or in a dedicated texture tool. Confirm the mid-level, the UVs, and the scale. Do not assume that a depth PNG will behave like a displacement texture just because both are grayscale.

If the next tool asks for distance from a camera, export depth. If it asks for movement along a normal, export displacement. If it asks for elevation from a base plane for a machine, export a height field. If it asks for surface direction for shading, export a normal map.

Write the convention into the filename or the manifest. The next person who opens the file should not have to guess what white means. A name such as height_white_high_16bit.png is not glamorous, but it prevents the most expensive class of mistake: a technically valid file applied in the wrong direction. Record the scale and the mid-level numerically as well, not only as a label, so the map can be recreated from the record alone.