UvMapping1

The objects in this simple scene are defined in geometry/demo.odb. The scene consists of a ground plane (using the build-in geometry), a sphere (using the build-in geometry) and five instances of a cube (using an external OBJ file):

The scene has two rows (foreground and background) each containing three objects. The sphere object is centered in the background row. The first two instances for the cube.obj object create a pair of cubes that flank the sphere in the background row. The last three instances embed the cubes in the ground (note the negative Z in the translation) and rotates them around Z. The instances for each cube are rotated with respect to the global XY coordinate system. However, the UV coordinate system defined by the OBJ geometry file will translate, scale and rotate with those instances.

The materials across the surface of the sphere and box objects are remapped via material map in the scene file. The general material map setup is shown below:

The details of the setup are beyond the scope of this demo, however the choice of the projector is important. The two possible <projector> options will be discussed in the following sections.

The image below is the output of the UV projection simulation (uv_map.sim) in the built-in image viewer using the "Selected Min/Max Scaling". The three square tiles in the foreground are the OBJ cube object inserted below the ground to isolate the top surface. These three instances were assigned Z rotation, and the mapped pattern rotates with the objects. The two cubes in the background are the same OBJ cube, but they are placed higher so that the map can be seen to wrap around the side surfaces. The right cube is rotated about multiple axes but the map "sticks" to the sides because the UV coordinate system provided in the OBJ file rotates with the object. The sphere object (background center) features a built-in UV coordinate system, which is similar to a latitude and longitude coordinate system. At the top of the sphere the UV coordinates "compress" as the coordinates converge. Note that in the animation, the map follows the objects in motion because it is tied to an inherent coordinate system associated with the object.

The image below is from the "vertical drape" projection simulation (drape_map.sim). In this case, you can see how the checkedboard pattern completely ignores the orientation of the various objects. The foreground row of three square tiles all have the checkerboard oriented with the global XY coordinates rather than rotating with them. The background row of objects show the major limitation of the global XY projection, as the left-rear cube features vertical surfaces "smeared" with the same value because those locations on the sides of the box have the same global XY coordinate and, hence, project to the same map image pixel. Note that in the animation, the map does not follow the object in motion because it tied to the global coordinate system rather than one associated with the object.

The UV coordinates are included in the Intersection truth. The image below contains an RGB visualization of the U coordinate, V coordinate and image radiance assigned to the red, green and blue channels, respectively. Although the specific RGB colors do not convey information, the patterns in these colors can be used to visualize how the UV coordinate system moves with each instance. For example, coordinate color pattern on the three square tiles in the foreground can be seen to rotate with each tile.