Geometry
This factor can be found at numerous locations throughout Cinema 4D when importing or exporting foreign formats. Therefore, don’t be surprised if the term ,export’ is used if this factor is seen in an import function (this factor is explained as a whole here).
This factor lets you scale files upon import/export, i.e., practically all relevant numerical values saved in the file or those to be saved will be multiplied by this factor and then saved - or interpreted when loaded.
The unit at the right in turn defines how upon
- Import the numerical value saved in the file is converted to the current Cinema 4D unit. Example: if an X value of 1 is saved in the file and you define Feet, the X value will be converted to 30.48 cm in Cinema 4D (if centimeters are defined by default in Cinema 4D).
- Export numerical values are saved in the file. Example: an X value is set to 100 cm in Cinema 4D. If you define Feet for export, the exported file will save a numerical value of 3.281 (1 meter = 3.281 feet).
More information about units and scaling can be found in the Project Scale section.
Use this setting to define if and how the objects to be imported should be structured. If multiple objects are created they will all be placed under a single Null object.
Each object defined as such in the OBJ file (these are named "o" in the OBJ file) will also be imported as a separate object. When splines are imported, individual splines will be created.
Surfaces with the same material will be combined to a single object. Make sure select the correct option for the Material setting. If you do not allow *.mtl files to be read, the Splitting setting will be rendered useless.
If this option is enabled, polygon groups of the same name will be brought together as a single object.
Polygon groups (these are denoted in the OBJ file with a "g") defined in the OBJ file will each be seen as 1 separate object.
All polygonal objects will be combined into a single object mesh. Different materials will be assigned via polygon selections. When importing splines, al splines will be combined as spline segments in a single spline.
Lines in the OBJ file correspond to the Linear spline Type in Cinema 4D and will also be imported as such by default.
The Splitting setting described above defines how the line segments are organized (whether as separate splines or as a single spline). The following options are available:
The lines will be imported as splines. Depending on the OBJ file, open contours can result with the last spline segment being open. If this is the case, use the next option.
The spline will always be imported with the Close Spline option enabled, i.e., the spline segments will always be closed. The first and last points will be connected. If spline start and end points lie on top of each other, the 
Optimize command can be used to melt these points.
A polygonal object made up of triangles will be created from each polyline. This works best with polylines that lie on a single plane and, ideally, form a closed outline. This produces the best shapes.
The following options are available when importing UV coordinates:
No UV coordinates will be imported.
UV coordinates will be imported as they are in the OBJ file and will not be modified.
UV coordinates will be flipped correspondingly.
UV coordinates will be flipped horizontally and vertically.
Use this setting to define if vertex Normals should be imported/exported. Phong tags can be generated for import.
No information pertaining to Normals will be processed (and no Phong tag will be created upon import).
Selecting this option will cause a Phong tag to be generated. The Phong Angle can be adjusted using the setting of the same name below.
An OBJ file's Vertex Normals information will be imported into Cinema 4D using a Vertex Normals tag. If Vertex Normals information is present, regular Phong shading via a Phong tag will be used.
If Normals is set to Phong tag, the Phong tags that are created can be smoothed using this setting.
The following applies:
- Standard Renderer: Vertex colors will be imported directly as assigned material via the Vertex Map shader
-
Redshift: If vertex colors are rendered using Redshift, proceed as follows:
1. Open the material in the Node Editor and create a Vertex Attribute Node. Drag the Vertex Color tag onto the Attribute Name field.
2. Connect the outColor port (vertex attribute) with the Base/Color (Default material).
The OBJ format always assumes object axes from the world origin. Other object positions or orientations in the OBJ file are achieved only via object point positions. Once such a file is imported it can be modified as usual (the 
Axis Center command can be helpful).
Since the OBJ format is such a commonly used format and different applications use different axis systems (with almost any imaginable axis combination, even with the Y axis pointing to the rear), these settings let you adjust the axes accordingly.
When importing certain OBJ files, for example, an object can literally be stood on its head. Enabling the Flip Y Axis option can prevent this from happening. Or you can switch the X and Y axes when exporting to a particular application because it has a different axis system. To do so, simply enable the Swap X and Y Axes option.
If this option is enabled, all polygon Normals will be flipped upon import/export.