Essential Guide to 3D Rendering: Process, Techniques, and Examples

3D rendering is everywhere: real estate, online shopping, gaming, movies and more. Learn about the art and science of 3D visualizations from artists and experts in the field.

What Does 3D Rendering Mean?

3D rendering is a computer graphics process that uses three-dimensional data and models. The goal is to create a lifelike or non-photorealistic image. 3D models are digital files of an object created using software or through 3D scanning.

3D rendering is also a form of virtual photography. The staging and lighting of scenes are fundamental to the generation and capture of images, whether photorealistic or intentionally non-realistic.

Ben Rubey, 3D Art Lead for Marxent, explains, “3D rendering is the act of creating a 2D image from a 3D scene. Compare it to taking a photo with a camera. In 3D rendering, you take all of the 3D data and turn it into a snapshot of the scene.”

Two Types of Rendering: 3D Real-Time and 3D Post-Process Rendering

3D real-time rendering produces and analyzes images using graphics software, usually to create the illusion of motion from 20 to 120 frames per second. 3D post-processing rendering is done on a 3D render once it reaches a stage acceptable to the artist. Post-processing fixes minor errors and adds details for additional realism, usually with editing software.

3D Rendering vs. 3D Visualization

3D visualization is the system of multidisciplinary procedures that create a convincing image that looks like it exists in a real space, from concept to the final representation. 3D rendering is one of the final steps in 3D visualization.

3D Modeling vs. 3D Rendering

3D modeling is the process of developing a mathematical representation of an object or surface as it would appear by width, breadth, and depth dimensions. 3D rendering transforms 3D modeling into high-quality, detailed, and lifelike images.

3D modeling and 3D rendering are two separate steps within computer-generated imagery (CGI) creation. 3D modeling precedes 3D rendering in the 3D visualization process, and modeling services are often purchased. Learn more about the process and how to outsource modeling services.

What Is 3D Product Rendering?

3D product rendering generates 2D images from models. 3D product renderings create photorealistic images that show how an object will look after manufacturing. The product is usually rendered to show multiple angles.

Many industries benefit from 3D product rendering before the manufacture of products. For example, 3D product renderings can help test a product’s appeal to customers before it goes to market, reveal design defects, and save development costs.

How Does 3D Rendering Work?

3D rendering is a multistep process to render a product or complete scene into a 2D representation. Rendering can take milliseconds or many days for a single image or frame with the method used for video or feature films.

Steps in the 3D Rendering Process

The 3D rendering process begins with a consultation and a resulting vision. Next, there is analysis and design, which is the basis for modeling. 3D rendering comes after, followed by refinement processes. Once the render is approved, it is delivered.

Rendering steps may differ depending on the project, the type of software used, and the desired outcomes.

Pre-Rendering Steps

Before rendering begins, consider these three steps, which are separate and foundational to the process:

Vision: Before any work begins, hold an initial consultation to understand the goals of the project: the company, its market, appearance, and intended use of the image. Based on that input, it is easier to determine what the final deliverable will be. The client or creative director then approves the vision.

Analysis and Design: With the approved vision in mind, project analysis begins, and decisions about object rendering are determined. Decide on any features it should contain in the finished product, such as color, texture, camera angles, lighting, and environment.

Modeling: 3D modeling produces a 3D digital representation of a surface or object. Using the software, the artist manipulates points in virtual pace (called vertices) to form a mesh: a collection of vertices forms an object or a solid. The solids generated are geometric shapes, usually polygons (also known as primitives). The polygons are manually or automatically generated by manipulating vertices. If the desired outcome is special effects or character animation, the digital object can be animated.

“3D modeling is about the creation of objects, like a chair,” Rubey notes. “In 3D, a chair can exist as a geometry, the shape of the object, but it is invisible until the camera captures it, renders it, and adds the materials, lighting, color, and texture.”

3D Rendering Steps

After modeling, the 3D artist begins his work to bring the scene to life. “The best way to make sense of 3D is to compare 3D objects to objects in the real world,” Rubey explains. “Let’s say I want to render a spoon that’s sitting in my kitchen. First, I need to draw or capture the shape or geometry of the spoon in 3D. Then I add the material I want: clear plastic, opaque plastic, wood, or stainless steel that either has a shiny or matte finish. Then bring in the lighting to add dimensionality. This final stage is what makes the object look real.”

“Finally, you decide the camera’s position and take the pictures. We can put a camera above, below, and facing–just as in real life. Then you can take one image or an animation that is a series of images, as is the case in cinema or film. When you take a picture in real life, the lens opens to take in the light. In 3D, it’s the same, but the computer does the mathematical calculations of the light quality and angle. The more elements, the more lights, the longer it takes to create an image.”

1. Rendering: Materials and Texture

An accurate depiction of the object’s material is essential to realism. The artist changes the material settings and appearances, like glossy plastic or matte linen, to get a realistic visual representation. Other parameters are changed, such as the surface or even the hardware used to install it.

2. Rendering: Lighting

Light is everything, according to Rubey. “A good lighting person in 3D understands the physics of light and reflection. Lighting creates shadows; shadows make objects appear real. Without convincing lighting, the products look fake and unnatural. People don’t necessarily understand why they think something looks fake, but it largely has to do with a lack of realistic lighting, reflections, and shadows.”

3. Rendering: Details

After texturing and lighting, the 3D artist will continue to sculpt and add details to complete the concept, whether the goal is to make the form as close to lifelike as possible.

4. Rendering: Feedback and Refinement

The client or art director’s feedback is collected to make any refinements or changes. The artist incorporates the input, makes any changes, and submits the image for final approval.

5. Delivery

The final image is provided to the client or stored for use in a more extensive image sequence. The resolution and format of the pictures depend on the ultimate use: print, web, video, or film.

The 3D Rendering Artist

3D rendering artists are unique craftspeople since they are both creative and appreciative of technology. Many 3D artists have experience in the arts or industrial design and convert their skills into digital form. In industrial design, 2D markers are created and highlighted to create products like cars, which is also called rendering.

Julian de Puma is a fine artist and a 3D artist with more than 25 years of gaming and engineering visualization experience. de Puma says that flexibility was an advantage in the past but that employers today often look for specialists. “For example, mechanical and industrial design clients use software tools that are high-end and more expensive because they require precision. Those artists tend to have more of an engineering brain. Organic rendering is more like working in clay, creating dragons, monsters, people, soft stuff, and more akin to traditional drawing or painting. I can do both but prefer the more organic subjects.”

No matter what type of work the 3D artist does, continuous learning of new programs is part of today’s profession. While technologies are coming at an ever-faster pace, de Puma notes, “They do tend to make things easier and faster, which is a good thing.”

Different 3D Rendering Techniques

Photorealism, or the illusion of reality in non-realistic images, is one of the main goals of 3D rendering. Most techniques focus on creating believable perspective, lighting, and detail.

Types of 3D Rendering

• Real-Time or Interactive Rendering: Real-time rendering is used primarily in interactive and gaming graphics, where images process from 3D information at high speed. The dedicated graphics hardware has improved the performance of real-time rendering, ensuring rapid image processing. “The best example of real-time rendering is a video game,” Rubey explains. “It’s happening right now with renders moving at 60 frames per second. Marxent has a product that shows rendering in real-time: 3D Room Planner. When you want to render in high quality, the computer calculates how the natural shadow looks. It takes a few minutes to figure out the more realistic scene.”
• Non-Real-Time or Offline Pre-Rendering: Typically used in situations where the need for processing speed is lower, this method is employed when photorealism needs to be at the highest standard possible for visual effects. Unlike real-time rendering, there is no unpredictability in the process. “A Pixar animated movie takes an hour to render a single frame,” notes Rubey.
• Multi-Pass Rendering: This post-production process divides an image into separate layers. Each layer is tweaked to optimize the image overall. The technique adjusts color and lighting intensity to preserve details. Video games, computer-generated movies, and special effects use this technique to create more realistic scenes.
• Multiple passes usually happen in films to improve the final image. At Marxent, we render one frame. In 3D, we separate the rendering into passes: one pass just of the shadows, one pass just of the reflections, another pass just for colors. We take these passes and put them into compositing software, layer them, and change each aspect independently of the other, making the shadows lighter or darker. Many different passes provide better results with more control – like Photoshop, but for animation.”
• Perspective Projection: This technique makes distant objects appear smaller relative to those closer to the viewer’s eye; the software program will create perspective projections by multiplying a “dilation constant” to set objects into scenes appropriately. A dilation constant of one means no perspective, while a high dilation constant can cause image distortion or a “fisheye” effect. Orthographic projection, which views objects along parallel lines perpendicular to the drawing, is used for scientific modeling that requires precise measurement and third-dimension preservation.
• Radiosity: This technique simulates how surfaces act as indirect light sources for other surfaces when illuminated. Radiosity produces realistic shading that mimics the way light diffuses in real-world scenes. The diffused light from a specific point on a particular surface is reflected in a broad spectrum and lights the virtually rendered space.
• Rasterization: With this technique, the “classic” for 3D rendering, objects generate from a mesh of polygons or virtual triangles or polygons to create 3D models. In this virtual mesh, the corners (vertices) of each triangle intersect with the vertices of triangles of different shapes and sizes. Data is associated with each vertex, including its spatial position, texture, and color.
• de Puma explains rasterization in gaming: “Low-polygon modeling keeps old or weak processors from bogging down. That way, you can do real-time animation on older systems. Or you can run lots of characters in a scene. Use low-poly modeling in mobile gaming, where high-resolution characters and objects aren’t necessary. In modern games, running on modern systems, high-resolution characters are made with varying levels of detail (LOD); as characters get farther from the camera, their detail drops. They shed polygons. Their texture resolution drops as well.”
• Ray Casting: This is a fast technique that detects visible surfaces. The 3D artist allots the location and sets the point of view, which usually incorporates a 60-degree field of vision. Within the virtual space, the artist positions light sources. Light rays trace individually, and ray intersections are determined. Based on these intersections, what is visible based on the POV is determined.
• Ray Tracing: By tracing light paths as pixels in an image plane, this technique simulates how it meets with virtual objects. Ray tracing is slower than ray casting.
• Resolution Optimization: 3D rendering image resolution depends on the number of pixels used to create the image. The higher and denser the number of pixels in the image, or pixels per inch, the sharper and clearer the final image will be. The resolution depends on how realistic the image needs to be.
• Scanline Rendering / Wireframe: This is an algorithm for visible surface determination. Rather than scanning on a pixel-by-pixel or polygon-by-polygon basis, it scans an object row by row.
• Shading: Shading is a rendering process that computes the color of objects in a scene from a given viewpoint. An example of shading is texture mapping.
• Texture Mapping: Texture mapping defines surface texture, color or high-frequency detail. It vastly reduces the number of polygons and lighting calculations when constructing a photorealistic scene in real-time.
• Transport: This technique displays how light in a scene moves from one area to another. Visibility is the main factor in light transport.
• Z-buffering: Also known as depth buffering, z-buffering helps determine whether a complete object or part of an object is visible in a scene. It is used in software or hardware to improve rendering efficiency.

How to Composite a 3D Render

A composite is a post-3D rendering step. The process assembles render passes and layers. Along with adding realism, it is a time- and money-saving step since it adjusts images faster than rendering.

Compositing Example

Here is a sequence from the video game Grand Theft Auto that shows how data sets can be manipulated to enhance photorealism: