This tutorial will be using the Blender Cycles Render Engine in Blender 2.70.
Say you have a picture you want to use in your render. For example, this one:
You Import the Picture as a Plane and hang it on your virtual wall in your render. You think it might look nice up there, but you’re wrong! Look closely to at this picture:
You may notice that it doesn’t look very realistic. The picture on the wall doesn’t seem like it’s really there. You made the material correctly, you added the lamps properly, what’s wrong?
The Bump Mapping.
Yes. Most things need a slight bump map to make it look realistic. (Bump mapping is also know as Displacement, but actually, Displacement is when a mesh is modified based on an image map. Bump mapping is when no mesh is changed, but a texture effects how light hits the model. ) It’s not only the picture hanging on the wall that needs a bump map, but also the wallpaper.
To add a simple bump map (using Cycles), just add an Image Node (or use your existing node), and Mix Node (not a Mix Shader node). Connect the Image Node to the bottom of the Mix Node. Change the top color of the Mix Node to white. Connect the Mix Node to the Displacement Input of the Material Output Node. Now if you change the Mix slider value, it will change the intensity of the bump map.
NOTE: Bump maps will not show up very well on a basic Diffuse material. I recommend adding a very slight Glossy Node mixed with a Diffuse. It will add more detail. (See image)
Here’s the finished result. The difference may not be noticeable at first, but it adds a lot more depth to the picture and more realism too.