Summary
This video introduces three fundamental 3D modeling techniques—skewing, extruding, and beveling—applied to 2D perspective drawing for modifying basic shapes. The tutorial provides step-by-step instructions for each technique, such as using duplication methods for skewing boxes and cylinders, and utilizing face centers and diagonals for precise extrusion. Detailed examples, including a chest of drawers and beveled cylinders, demonstrate how these tools build upon previous perspective knowledge. Mastering these modifiers is essential for constructing complex, realistic objects and serves as a foundation for more advanced techniques like filleting and smoothing.
Key Insights
Skewing involves shifting one part of a shape while keeping another stationary to create angled forms.
Skewing is achieved by drawing a basic shape and then shifting a specific plane, such as the top of a box, in a specific direction while the base remains fixed. To ensure accuracy, measurements and division methods are used to duplicate the object to the side, providing a guideline for the new position of the shifted plane. Once the new position is established, the corners are connected back to the original base, creating a skewed perspective. This technique applies to both rectangular forms and cylinders, where the top ellipse is shifted relative to the bottom one.
Extrusion is the process of pushing out or pulling in a part of a shape's face to create depth and complexity.
To extrude a specific portion of a face, one must first find the center using diagonals. By selecting points along these diagonals and connecting them to vanishing points and vertical lines, a recessed area is defined within the existing face. These points are then projected out along the lines of perspective to create a new, protruding volume. This tool is vital for mechanical objects and can be layered repeatedly to build complex structures from a single basic box, effectively mirroring 3D modeling workflows.
Beveling combines extrusion and skewing to create angled inclines that add realism to objects.
Beveling is essentially an extrusion performed on an incline rather than straight lines. The process begins by defining a recessed area on a face, similar to extrusion. However, instead of connecting the new protruding face to the original with lines parallel to the perspective axis, they are connected with angled lines. This creates a sloped transition. In reality, perfectly sharp edges are rare, so beveling is a crucial technique for making drawings look more believable and representational of physical objects.
Sections
Introduction to Modifying Basic Shapes
The tutorial covers three primary 3D modeling techniques tailored for perspective drawing: skewing, extruding, and beveling.
The lesson introduces three core principles used in 3D modeling that can be adapted for drawing and design to modify basic geometric shapes. These tools—skewing, extruding, and beveling—are essential for fitting basic shapes to specific design needs and serve as the foundation for complex object construction.
Skewing Shapes
Skewing is the act of moving one part of an object in one direction while the base remains stationary.
The instructor defines skewing as shifting one segment of an object while keeping the other part fixed in place. To demonstrate, a box is drawn, and the goal is to move the top portion toward a vanishing point to create a skewed effect while the bottom remains as the original base.
Calculated duplication and division methods are used to determine the exact shift and degree of the skew.
To skew a box accurately, the center of the face is found and connected to the vanishing point. By connecting corners to the new edge center, the box is duplicated to the right. The top of this new box serves as the guideline for the skewed top, which is then connected back to the original base. This method allows the artist to decide the precise amount of shift before final drawing.
These skewing and shearing techniques are equally applicable to cylinders and divided box parts for various modifications.
The same duplication process applies to cylinders by moving the top plane's ellipse to the side and connecting it to the bottom ellipse. Additionally, shearing can be achieved by dividing a box into parts and moving those parts individually to create complex, modified shapes.
Extruding Shapes
Extrusion is a critical tool for creating mechanical and inanimate objects by extending parts of a face.
Extruding is presented as a highly useful tool for developing mechanical details. While previously identifying how to duplicate entire faces, this section focuses on how to extrude only a specific portion of a face, which involves more intricate geometry within the shape's boundaries.
Finding the center and utilizing diagonals allow for the precise outline of a recessed area for extrusion.
To extrude a part of a box, the center of the face is found using diagonal lines. Points are chosen on these diagonals to define the boundaries of the area to be extruded. These points are connected to vanishing points and projected vertically to establish the new face, which is then pushed out from the original box by connecting edges to the vanishing points.
Repeated extrusion is a valuable exercise for building complex 3D-like shapes from simple foundational boxes.
The instructor demonstrates that once an extrusion is complete, the back lines of the original box are hidden to maintain perspective. This process can be repeated infinitely, allowing artists to fill a page with extrusions from a single box. This is a practical way to rough out complex shapes before smoothing them, much like the workflow in 3D modeling software.
Example: Drawing a Chest of Drawers
A chest of drawers example illustrates how extrusion handles multiple internal components like open or closed drawers.
Using a chest of drawers as a practical application, the front face is divided using centers and diagonals to outline the recessed area for the drawers. The area is split in half for two drawers, and then each individual section's center is found to define the final drawer size.
The depth of drawers is controlled by extending points toward the vanishing point to represent protrusion.
To show the drawers opening, points from the drawer outlines are extended toward the vanishing point. The artist can decide how far each drawer is open—either the same distance or varied for realism. After drawing the final shapes, lines are cleaned up and overlapping hidden lines are removed to finalize the perspective.
Beveling Shapes
Beveling is defined as an angled extrusion, effectively mixing the principles of skewing and extruding.
Beveling creates a sloped edge instead of a straight 90-degree angle. It begins by finding the center of a face and recessing the area, just like extrusion. In a two-point perspective, the face is extruded vertically, but the key difference is that the new face's corners are connected to the original base corners with angled lines rather than vertical ones.
Beveling is used to create more believable objects since perfectly sharp vertical edges are rare in reality.
The instructor explains that beveling adds a level of realism to drawings that straight extrusions cannot achieve, as most real-world objects have slightly angled or rounded edges. This technique can be layered, where a shape is beveled, then another smaller area on top is beveled again.
For cylinders, beveling can be done via a surrounding box or by manipulating ellipses directly in digital software.
A beveled cylinder (or chamfered cylinder) can be drawn by first beveling the surrounding bounding box and then inscribing ellipses within those boxes. Alternatively, in Photoshop, one can simply copy an ellipse, shrink it, move it vertically, and connect it with angled lines. Beveling can be applied to both the top and bottom of a cylinder for a symmetrical appearance.
Conclusion and Path Forward
The lesson concludes with an emphasis on practice and a preview of more advanced modifiers like fillets and smoothing.
The instructor stresses the importance of mastering these basic modifications—skewing, extruding, and beveling—because they appear in almost every perspective drawing. Future lessons will build on these concepts to explore more complex tools such as fillet, chamfer, smooth, and subdivisions, which will lead to even more sophisticated design capabilities.
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