From 9c4b1d9a1ca679b3d9a40536d9e3feea82b85c7b Mon Sep 17 00:00:00 2001 From: Wenzel Jakob Date: Thu, 18 Oct 2012 11:28:07 -0400 Subject: [PATCH] GUI documentation update pass, part 1 --- src/integrators/path/path.cpp | 2 +- src/integrators/path/volpath.cpp | 4 +- src/mtsgui/resources/docs.xml | 122 ++++++++++++++++++------------- 3 files changed, 76 insertions(+), 52 deletions(-) diff --git a/src/integrators/path/path.cpp b/src/integrators/path/path.cpp index ee30f208..98ab1c4e 100644 --- a/src/integrators/path/path.cpp +++ b/src/integrators/path/path.cpp @@ -37,7 +37,7 @@ static StatsCounter avgPathLength("Path tracer", "Average path length", EAverage * path termination criterion. \default{\code{5}} * } * \parameter{strictNormals}{\Boolean}{Be strict about potential - * inconsistencies involving shading normals? See \pluginref{path} + * inconsistencies involving shading normals? See the description below * for details.\default{no, i.e. \code{false}}} * } * diff --git a/src/integrators/path/volpath.cpp b/src/integrators/path/volpath.cpp index e52e8db6..4de5f467 100644 --- a/src/integrators/path/volpath.cpp +++ b/src/integrators/path/volpath.cpp @@ -44,7 +44,9 @@ static StatsCounter avgPathLength("Volumetric path tracer", "Average path length * This plugin provides a volumetric path tracer that can be used to * compute approximate solutions to the radiative transfer equation. * Its implementation makes use of multiple importance sampling to - * combine BSDF and emitter sampling strategies. + * combine BSDF and phase function sampling with direct illumination + * sampling strategies. On surfaces, this integrator behaves exactly + * like the standard path tracer. * * \remarks{ * \item This integrator will generally perform poorly when rendering diff --git a/src/mtsgui/resources/docs.xml b/src/mtsgui/resources/docs.xml index f8623160..f713104b 100644 --- a/src/mtsgui/resources/docs.xml +++ b/src/mtsgui/resources/docs.xml @@ -37,20 +37,23 @@

- This parameter specifies the action to be taken when the geometric - and shading normals of a surface don't agree on whether a ray is on - the front or back-side of a surface. -

-

- When strictNormals is set to false, the shading normal has - precedence, and rendering proceeds normally at the risk of - introducing small light leaks (this is the default). -

-

- When strictNormals is set to true, the random walk is - terminated when encountering such a situation. This may - produce silhouette darkening on badly tesselated meshes. + Be strict about potential inconsistencies involving shading normals?

+

Triangle meshes often rely on interpolated shading normals + to suppress the inherently faceted appearance of the underlying geometry. These + "fake" normals are not without problems, however. They can lead to paradoxical + situations where a light ray impinges on an object from a direction that is classified as "outside" + according to the shading normal, and "inside" according to the true geometric normal.

+

The strictNormals + parameter specifies the intended behavior when such cases arise. The default (false, i.e. "carry on") + gives precedence to information given by the shading normal and considers such light paths to be valid. + This can theoretically cause light "leaks" through boundaries, but it is not much of a problem in practice.

+

When set to true, the path tracer detects inconsistencies and ignores these paths. When objects + are poorly tesselated, this latter option may cause them to lose a significant amount of the incident + radiation (or, in other words, they will look dark). + The bidirectional integrators in Mitsuba (BDPT, PSSMLT, MLT, ..) + implicitly have strictNormals activated. Hence, another use of this parameter + is to match renderings created by these methods.

@@ -159,33 +162,48 @@ - - Direct-only integrator using multiple importance sampling. - Takes a user-specifiable amount of luminaire - and BSDF samples and combines them using the power heuristic - By setting one of the strategies to zero, this - plugin can effectively be turned into a luminaire sampling or - BSDF sampling-based integrator. Ignores participating media - if they are present. + +

This integrator implements a direct illumination technique that makes use + of multiple importance sampling: for each pixel sample, the + integrator generates a user-specifiable number of BSDF and emitter + samples and combines them using the power heuristic. Usually, the BSDF + sampling technique works very well on glossy objects but does badly + everywhere else, while the opposite is true for the emitter sampling + technique. By combining these approaches, one + can obtain a rendering technique that works well in both cases.

+ +

The number of samples spent on either technique is configurable, hence + it is also possible to turn this plugin into an emitter sampling-only + or BSDF sampling-only integrator.

+ +

For best results, combine the direct illumination integrator with the + low-discrepancy sample generator. Generally, the number + of pixel samples of the sample generator can be kept relatively + low (e.g. sampleCount=4), whereas the emitter and BSDF sample + parameters of this integrator should be increased until the variance in + the output renderings is acceptable.

 Number of samples to take using the emitter sampling technique Number of samples to take using the BSDF sampling technique

- This parameter specifies the action to be taken when the geometric - and shading normals of a surface don't agree on whether a ray is on - the front or back-side of a surface. -

-

- When strictNormals is set to false, the shading normal has - precedence, and rendering proceeds normally at the risk of - introducing small light leaks (this is the default). -

-

- When strictNormals is set to true, the random walk is - terminated when encountering such a situation. This may - produce silhouette darkening on badly tesselated meshes. + Be strict about potential inconsistencies involving shading normals?

+

Triangle meshes often rely on interpolated shading normals + to suppress the inherently faceted appearance of the underlying geometry. These + "fake" normals are not without problems, however. They can lead to paradoxical + situations where a light ray impinges on an object from a direction that is classified as "outside" + according to the shading normal, and "inside" according to the true geometric normal.

+

The strictNormals + parameter specifies the intended behavior when such cases arise. The default (false, i.e. "carry on") + gives precedence to information given by the shading normal and considers such light paths to be valid. + This can theoretically cause light "leaks" through boundaries, but it is not much of a problem in practice.

+

When set to true, the path tracer detects inconsistencies and ignores these paths. When objects + are poorly tesselated, this latter option may cause them to lose a significant amount of the incident + radiation (or, in other words, they will look dark). + The bidirectional integrators in Mitsuba (BDPT, PSSMLT, MLT, ..) + implicitly have strictNormals activated. Hence, another use of this parameter + is to match renderings created by these methods.

 @@ -202,27 +220,26 @@ - Volumetric path tracer, which solves the full radiative transfer - equation in the presence of participating media. - Simplified version without multiple importance sampling - this - version can be significantly faster than the extended - version when when rendering heterogeneous participating media using the - [Coleman et al.] sampling technique, as fewer attenuation - evaluations will be performed. + This plugin provides a basic volumetric path tracer that can be used to + compute approximate solutions to the radiative transfer equation. This + particular integrator is named "simple" because it does not make use of + multiple importance sampling. This results in a potentially + faster execution time. On the other hand, it also means that this + plugin will likely not perform well when given a scene that contains + highly glossy materials. In this case, please use the extended volumetric + path tracer or one of the bidirectional techniques. - Volumetric path tracer, which solves the full radiative transfer - equation in the presence of participating media. Estimates single - scattering using both phase function and luminaire sampling and - combines the two with multiple importance sampling and the power - heuristic. Afterwards, the phase function sample is reused to - recursively estimate the multiple scattering component, which saves an - intersection computation. - On surfaces, this integrator behaves exactly like the MI path tracer. + This plugin provides a volumetric path tracer that can be used to + compute approximate solutions to the radiative transfer equation. + Its implementation makes use of multiple importance sampling to + combine BSDF and phase function sampling with direct illumination + sampling strategies. On surfaces, this integrator behaves exactly + like the standard path tracer. @@ -250,7 +267,12 @@ hitting it via ray tracing. This is one of the worst conceivable rendering and not recommended for any applications. It is mainly included for debugging purposes.

- + +

The number of traced particles is given by the number of "samples per + pixel" of the sample generator times the pixel count of the output image. + For instance, 16 samples per pixel on a 512x512 image will cause 4M particles + to be generated.

+ Specifies the work unit granularity used to parallize the the particle tracing task (default: 200K samples per work unit).