Cycles : Bump mapping : Displacement

The textures in Blender, with the rendering engine “Cycles”, may incorporate a channel named “Displacement” which provides a surface roughness.

There are two different techniques:

• “Bump mapping” Mapped the topological
• “Displacement mapping” or displacement mapping.

In the first case will not change the geometry of the object but normal to the surface affect the surface illumination. In the second case the geometry is altered with a displacement of vertices in the rendering stage, thus, besides lighting effects, occlusions may be obtained from other objects in the scene.

Topological mapping (English, bump mapping) is a 3D computer graphics technique created by James F. Blinn one 1978. It consists in giving a rough appearance to the surfaces of the objects. This technique modifies the surface normals without changing its geometry. The original normal surface perpendicular thereto will. The topological mapping changes the normal perpendicularity other to achieve the desired effect, not modifying the topology and geometry of the object. The result is reasonably rich and detailed, and larger can be achieved similar to natural elements (as the texture of an orange). Mapping the difference between displacement (displacement mapping) and topological mapping is that the latter does not disturb the geometry, only the direction of the normal field.(W)

The following image is not associated with a displacement map. On a cylinder that has been modified to one end (cone) texture has been applied (photo material) Cork.

Textured Image without displacement maps

If we change the node editor adding material to the channel “Displacement” a new texture, create an effect of roughness on the surface. The technique used (“Bump mapping” or “Displacement mapping”)depends on the parameters that we have selected.

Bump Displacement Mapping

If we disconnect the texture (cork) keeping the displacement map, to see its effect in isolation, we have the following picture in which the smooth surface of the cylinder, when illuminated, shadows occur as if roughened.

Displacement map on a cork

Applying texture that brings the color we see that the image takes on a new look, rougher on surfaces of objects. In this case we have applied a “Bump mapping” and therefore only modified the effect of light strike the surface.

Material with color texture and bump mapping

If we add real movement with vertices “Displacement mapping” increase the realism of the image at the cost of increased rendering time.

Actual displacement

By comparing the techniques we see as realism of the object increases without increasing geometric complexity.

• In the left image a texture has been applied based on a photograph of a cylindrical.
• In the center image has been added bump mapping that modifies the surface normal giving a feeling of roughness. If you look at the edge of the cork we see that has not changed its contour.
• In the third image (right) has applied a displacement map topological; although the form cylinder remains, the points are moved in accordance with the map rendering applied. It can be seen as the outline is straight and no longer reflects these shifts.

Bump mapping techniques comparing displacement and topological

Mapped topological effects of displacement and

Los mapped described affect as you seen in the way:

• Modify the surface normals creating shadows
• Modifying the vertex and thus the shape of the object

Mascara for displacement effects

Topological displacement maps (“Bump mapping”) affect only the shadows that produces the object by altering the direction of the surface normal.

If we change the position of the lights in the scene see how shadows change sn the area affected by these maps.

The applied texture mask or alter determine how each point of the surface. Null values (black) not modify the points, while the maximum values (white) create a greater effect offset.

If we apply the previous texture (circles) on a plane and modify the point light we see how it changes the shade, as shown in the two images accompanying. The first one has set its light to the right of the plane; The second is moved to the left.

Position right light

Position light left

The effect of the texture map may be controlled in intensity. If we introduce a multiplier node

Add->Converter->Math

we can increase the displacement map effect

Displacement material controlled with a multiplying effect modifier

For example, to a value 100 factor, get:

Displazament multiplier = 100

While if we increase to 1000, the result will be:

Displazament multiplier = 1000

Thus we see the possibilities of creating an effect of roughness without creating complex geometries, namely, without increasing the number of vertices of the geometry and consequently reducing the time of calculation of the images having fewer polygons.

The shape of the surface and the volume inside it may be altered by the displacement shaders. This way, textures can then be used to make the mesh surface more detailed.

Depending on the settings, the displacement may be virtual, only modifying the surface normals to give the impression of displacement, known as bump mapping, or a combination of real and virtual displacement.(Wiki Blender)

Again we see the difference between bump mapping and displacement topological. In this case it is appreciated that the surface deforms. This difference is critical because when displacement occurs the effect is more visible from any direction, while if there is not it will become clear only when you look perpendicular to surfaces. Another important aspect is that in the case of displacements can occlude (cover) objects located behind the area affected.

Bump mapping

With displacement:

Displacement topological

Activation

In “Cycles”, version 2.63, the displacement effect has not been completed to integrate. It is under development and therefore has been implemented experimentally. Once activated rendering mode “Cycles”, mode we “Experimental” to access the actual shift mode.

Render experimental

Then we enter the menu “Object Data” to modify the properties of the object to use the displacement: We will select the type of normal mapping (“Bump”) or displacement of vertices (“True”), may choose a combination of both (option “Both”)

Select type of displacement

• Mapas de normales : bump mapping : Mapeado topológico
• Cycles Renderer: how to correctly setup bump maps