A Survey on Gradient-Domain Rendering

Supplemental material

In this supplemental document, we provide the interactive comparisons for the results presented in the paper titled "A Survey on Gradient-Domain Rendering". The primal- and gradient-domain techniques included are:

Path tracing (PT)
Bidirectional path tracing (BDPT)
Vertex connection and merging (VCM/UPS)
Photon density estimation (PM)

The scenes are rendered for equal-time comparison. We first show interactive 4-way comparisons between our method and other methods. Each visual comparison includes:

Reconstruction images
Viridis error map: relative MSE mapped with viridis color map.
Red/green error map: positive (green) or negative (red) relative error to the reference.
Gradient images (brightened with +3 exposure value)

At the end of each result page, we show the convergence plot with the relative MSE and SSIM metric. SSIM metric is computed on tonemapped images. Click on the technique name to add or remove a curve inside the plot.

Scene	Equal-time comparison	Comments
Sponza	5 min	In this scene, all the surfaces are diffuse which is ideal for gradient-domain techniques.
Bathroom	15 min	In this scene, light sampling strategies are inefficient due to the difficult visibility.
Bookshelf	15 min	In this scene, some regions with SDS paths are challenging for path-based methods, e.g., the objects behind the glass on the bookshelf. In contrast, density-based methods works well for such regions. However, some other region, e.g., the light pool is difficult to render with only density-based methods. In this scene, G-VCM provide performs the best.
Torus	5 min	This is one of the classic scenes for progressive photon mapping. In this scene, the torus in the glass cube is lit by many SDS paths. This results in poor performance for path-based methods.