Hi Hady,

The concept of the crease pencil combines several options, I hope I got all:

You want to draw a spline in space.
Get the Sketch Pen (left side bar menu). If the created Spline is active, it will be added to this. Click in the Object Manager to deactivate, and it will start a new object.
Screenshot 2025-08-25 at 11.28.01 AM.jpg
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/TOOLSPLINESKETCH.html#PLUGIN_CMD_440000150
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Start drawing. If you are in the Perspective Editor View, it takes the World origin and places a "virtual plane" there. Changing the view changes the virtual Plane.
In front, right, top, etc, view it takes that view and draws flat on the world origin (the X, Y, Z = 0, 0, 0 point)
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If you need the plane elsewhere, use it and switch on Snapping > Polygons. Start drawing. The Plane is needed only during sketching; deactivate it or delete it as needed.
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/DMODELING-SNAP_SETTINGS.html#PLUGIN_CMD_440000121
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Splines can be rendered in various ways, depending on which render you like to use. Or use a Generator to create an object with it (Sweep and a Profile Spline, for example), while the RS Object Tag recognizes Splines and can turn those into virtual Geometry (render time)
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/TRSOBJECT-REDSHIFT_OBJECT_GROUP_CURVE.html?TocPath=Object%2520Manager%257CTags%2520Menu%257CRender%2520Tags%257CRedshift%2520Object%2520Tag%257C_____3
(Or with a Hair material)
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Splines can be projected to objects.
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/TOOLSPLINEPROJECT-MDATA_MAINGROUP.html?TocPath=Spline%2520Menu%257CProject%257C_____1
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For rendering outlines or other Toon Effects, use either Sketch 'n' Toons. (The Redshift Toon Shader comes to mind for Toon aesthetics.)
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/5545.html?TocPath=Sketch%2520and%2520Toon%257C_____0
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Painting directly on objects has been the duty of Body Paint 3D, or Paint, for a couple of decades, as the layout is now known. It needs a texture somewhere in the material. ( The Body Paint 3D Setup Wizard will support this with a few clicks.)
https://help.maxon.net/c4d/2025/en-us/Default.htm#html/11569.html#PLUGIN_CMD_170625
Think of Body Paint 3D as a Photoshop version for 3D, with Layers, but for up to ten different Material qualities (going by the Standard Material), each with its own layer version. So strokes can be left on separate layers. Body Paint 3D (BP3D) offers a vast array of Brushes for a wide variety of work. Note: BP3D offers direct painting on a surface, or projection painting, where one can paint on a virtual plane, which can be adjusted (moved) and, if found to be OK, projected to the object.
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As a side note, for more options, consider exploring the use of Cineware in Illustrator, as most graphic designers are more familiar with this app, if that is your pipeline.
https://www.maxon.net/en/cinema-4d/features/cineware-for-illustrator?srsltid=AfmBOopxELp3xhAw7xjzWbit25XjZsq2m9IuLU2Bf-kSCcM2PcC80_8k
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Not relevant here, but the Doodle is just a Doodle tool, nothing for deliveries. Think of it as a demo or brainstorming tool; it has no other ambitions.

Enjoy your exploration