Hidden Solid Removal: Ray-Tracing algorithm

Hidden Solid Removal

The hidden solid removal issue involves the view of solid models with hidden line or surface eliminated. Available hidden line algorithm and hidden surface algorithms are useable to hidden solid elimination of B-rep models.

The following techniques to display CSG models:

1.    Transfer the CSG model into a boundary model.

2.    Use a spatial subdivision strategy.

3.    Based on ray sorting.

 1.Ray-Tracing algorithm

A ray tracing is a method for creating an image by tracing the path of light via pixels in an image plane and reproducing the effects of its meets with virtual objects. The procedure is capable of creating a high degree of visual realism, generally higher than that of usual scan line techniques, but at a better computational. This creates ray tracing excellent suited for uses where the image can be rendered gradually ahead of time, similar to still images and film and TV visual effects, and more badly suited for real time environment like video games where speed is very important. Ray tracing is simulating a wide range of optical effects, such as scattering, reflection and refraction.

Fig.3.6. Ray-Tracing algorithm

Ray-Tracing algorithm

For every pixel in image

{

Generate ray from eye point passing via this pixel Initialize Nearest ‘T’to ‘INFINITY’

Initialize Nearest Object to NULL

For each object in scene

{

If ray intersects this image

{

If t of intersection is less than Nearest T

{

Set Nearest T to t of the intersection

Set Nearest image to this object

}

}

}

If Nearest image is NULL

{

Paint this pixel with background color

}

Else

{

Shoot a ray to every light source to check if in shadow

If surface is reflective, generate reflection ray

If transparent, generate refraction ray

Apply Nearest Object and Nearest T to execute shading function

Paint this pixel with color result of shading function

}

}

Optical ray tracing explains a technique for creating visual images constructed in three dimensional graphics environments, with higher photorealism than either ray casting rendering practices. It executes by tracing a path from an imaginary eye via every pixel in a virtual display, and computing the color of the object visible via it.

Displays in ray tracing are explained mathematically by a programmer. Displays may also incorporate data from 3D models and images captured like a digital photography.

In general, every ray must be tested for intersection with a few subsets of all the objects in the view. Once the nearest object has been selected, the algorithm will calculate the receiving light at the point of intersection, study the material properties of the object, and join this information to compute the finishing color of the pixel. One of the major limitations of algorithm, the reflective or translucent materials may need additional rays to be re-cast into the scene.

Advantages of Ray tracing:

1.     A realistic simulation of lighting over other rendering.

2.     An effect such as reflections and shadows is easy and effective.

3.     Simple to implement yet yielding impressive visual results.

Limitation of ray tracing:

Scan line algorithms use data consistency to divide computations between pixels, while ray tracing normally begins the process a new, treating every eye ray separately.