Hidden Surface in Graphics Multimedia

Introduction of Hidden Surface in Graphics Multimedia

• Hidden surface removal is an important part of the rendering process in computer graphics, as it enables the realistic and efficient rendering of 3D scenes.

Definition of Hidden Surface in Graphics Multimedia

• In computer graphics, hidden surface removal (HSR) or hidden surface elimination (HSE) is the process of identifying and removing surfaces or parts of surfaces that are not visible in a particular viewpoint/the final image.

Characteristics of Hidden Surface in Graphics Multimedia

• Hidden surfaces are created when one object blocks another object from view, and they must be removed to create a realistic 3D rendering of the scene.
• Hidden surface removal is a crucial step in rendering three-dimensional scenes, as it ensures that only visible surfaces are rendered, resulting in a more realistic image.

Algorithms or Techniques for HSR/HSE

There are several techniques used for hidden surface removal in graphics, but the choice of technique for hidden surface removal depends on the complexity of the scene, the hardware and software available, and the desired level of accuracy and speed:-

1. Back-face culling:

   • This technique removes all polygons whose normal vectors are pointing away from the viewer, assuming that these polygons are facing away from the viewer and therefore not visible.
   • This technique involves removing the surfaces of objects that are facing away from the viewer.
   • This is a simple and fast technique that works well for convex objects, but it can lead to errors for concave objects.

2. Z-buffering:

   • This technique maintains a depth buffer, or Z-buffer, which stores the depth of each pixel in the scene. As each pixel is rendered, its depth value is compared to the value stored in the Z-buffer. If the new pixel is closer to the viewer, it replaces the previous value in the buffer. This allows the renderer to determine which surfaces are visible and which are not..

3. Painter’s algorithm:

   • This technique involves rendering the objects in the scene in order of their depth, from back to front.
   • This ensures that each object is drawn on top of the previous one, making the object visible if it is in front of another object.

4. Scanline rendering:

   • This technique involves dividing the image into horizontal lines and rendering each line individually, using depth information to determine which pixels are visible.

5. Ray casting:

   • This technique involves tracing rays from the viewer through each pixel in the scene to determine which surfaces are visible. This can be computationally expensive, but it can produce very accurate results.
   • This technique involves tracing rays from the viewer through each pixel in the scene and determining which surfaces the rays intersect. This technique can be slow and computationally expensive, but it is accurate and can handle complex scenes.

6. Binary space partitioning (BSP):

   • This technique involves dividing the scene into two parts using planes. Objects are then sorted into the parts of the scene based on their position relative to the planes. BSP trees can be used to efficiently traverse the scene and identify visible surfaces.

7. Occlusion culling:

   • This technique involves identifying objects or parts of objects that are completely hidden from the viewer’s viewpoint.
   • These objects can be removed from the scene, reducing the amount of rendering required.

Use/Applications of Hidden Surface in Graphics Multimedia

• The use of hidden surface removal in computer graphics is essential for creating realistic and visually appealing 3D scenes that can be used in a variety of applications, including gaming, virtual reality, and architectural design. Without hidden surface removal, the viewer would see all surfaces of a 3D object, even those that are not visible due to their position and orientation.
• Improving rendering speed: By removing surfaces that are not visible, hidden surface removal algorithms can significantly reduce the number of polygons that need to be rendered, improving rendering speed.
• Enabling interactive graphics: Hidden surface removal is crucial for interactive graphics, such as video games, where high frame rates are necessary for a smooth and immersive experience.
• Enhancing visual clarity: By removing hidden surfaces, the remaining visible surfaces become clearer and more distinct, enhancing visual clarity.
• Reducing memory usage: Hidden surface removal algorithms can reduce the amount of memory required to store 3D objects and scenes, which is particularly important for real-time applications where memory usage is limited.