Hi
There are three ways to use a height map in 3D.
1. Apply it to the surface as a bump map. This simulates height and can be useful for small textural height variations. It works in one direction only with white away from the and black down into the surface. Note though that the model itself is not changed, the height texture is merely simulated during the render stage.
surfaceIn Photoshop you would apply such a map in the bump texture and control its strength with the bump slider.
2. Convert the height map to a normal map then apply that to the surface. A normal map can affect the light in three directions (at 90 degrees to each other) but again is only a simulation used at the render stage and does not effect the actual model. It is a good way of simulating surface detail but is of course limited in the amount of displacement and another limitation is clearly seen on say the straight edges of a cube - where those edges remain perfectly straight despite apparent variations in the surface.
3. Use the height map for actual displacement of the model surface, rather than simulating it at render time. This does affect the model and can therefore be very realistic requires sufficient polygons for the model to be displaced at each point. That can increase the computing requirements considerably. In Photoshop that is limited to the surface of a plane. For displacing the surface of more complex objects, you would need to use a 3D application such as Blender 3D which can handle real displacement and also offers adaptive subdivision, where the model is divided more close to the camera than it is distant to the camera. This can save considerably on the memory and calculation requirements.
Dave
2
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