Dan_Ritchie

09-05-2014, 06:36 PM

Below is a video explaining how Lightwave can be turned into a path tracer, and several example images. A path tracer is based on a physically accurate rendering equation. Note that attributes like light reflections (specular), soft shadows, radiance, and caustics are naturally part of the equation. *See the "Some more nodes" thread for the nodes mentioned in the video.

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https://vimeo.com/105399601

In the old days of computer 3D rendering, limited processor power forced coders to use approximations of various rendering equations, such as Lambert shading and Phong highlights. These approximations were based more on mathematical observations than on natural phenomenon.

Over the last several decades, many additional approximations have been added to further simulate the appearance of natural phenomenon. Raytraced and shadow mapped shadows, ambient occlusion, radiosity, caustics, bent normals, and any of a thousand other techniques have been added to the original approximation, complicating the rendering equation beyond reasonable measures.

The point of Path Tracing is to return the rendering equation to its simplest form, while eliminating approximations in favor of a real world lighting solution.

Path tracing assumes that a surface spot's color (its shading) is the sum of all light that hit that spot. No other techniques are required to gain a host of extra lighting effects, such as soft shadows, ambient occlusion, caustics, global illumination, or radiated light. It's all part of one equation.

Path tracing eliminates the idea of separate object types for geometry and lights. Only geometry is used in path tracing. All illumination comes from geometry.

Path tracing uses brute force methods, and accumulates light by sampling from random directions. The simplicity of the equation keeps the rendering time at reasonable levels. By convention, a grainy intermediate (and continually refined) image is created and averaged until a desired level of smoothness is reached. Several levels of refinement will produce a discernible image, while several hundred passes may be needed to produce acceptable levels of refinement.

The benefit of path tracing over other methods is its physically accurate method, it's ability to produce discernible results in a short amount of time, and it's simplicity of implementation due to eliminating many extra steps to produce realistic results. Physical accuracy is just the nature of the algorithm itself.

124053

124054

124055

https://vimeo.com/105399601

In the old days of computer 3D rendering, limited processor power forced coders to use approximations of various rendering equations, such as Lambert shading and Phong highlights. These approximations were based more on mathematical observations than on natural phenomenon.

Over the last several decades, many additional approximations have been added to further simulate the appearance of natural phenomenon. Raytraced and shadow mapped shadows, ambient occlusion, radiosity, caustics, bent normals, and any of a thousand other techniques have been added to the original approximation, complicating the rendering equation beyond reasonable measures.

The point of Path Tracing is to return the rendering equation to its simplest form, while eliminating approximations in favor of a real world lighting solution.

Path tracing assumes that a surface spot's color (its shading) is the sum of all light that hit that spot. No other techniques are required to gain a host of extra lighting effects, such as soft shadows, ambient occlusion, caustics, global illumination, or radiated light. It's all part of one equation.

Path tracing eliminates the idea of separate object types for geometry and lights. Only geometry is used in path tracing. All illumination comes from geometry.

Path tracing uses brute force methods, and accumulates light by sampling from random directions. The simplicity of the equation keeps the rendering time at reasonable levels. By convention, a grainy intermediate (and continually refined) image is created and averaged until a desired level of smoothness is reached. Several levels of refinement will produce a discernible image, while several hundred passes may be needed to produce acceptable levels of refinement.

The benefit of path tracing over other methods is its physically accurate method, it's ability to produce discernible results in a short amount of time, and it's simplicity of implementation due to eliminating many extra steps to produce realistic results. Physical accuracy is just the nature of the algorithm itself.