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vector photonmap(string mapname, vector position, vector normal, ...)
void photonmap(string mapname, vector position, vector normal, vector &color, float &area, ...)
Variadic arguments
You can specify additional keyword,value argument pairs to set the behavior of the evaluation. These arguments must be defined at load time (literals or parameters).
To specify one of the additional arguments, pass the keyword as a
string, with the next argument being the value for the keyword. For
example ..., "wrap", "clamp", "border", {.1,1,1}).
Keyword |
Type |
Value |
|---|---|---|
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Maximum number of photons to filter to produce the final color.
Default is |
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How to interpret the photons.
Scale each photon by the Lambertian cosine law.
Use the raw energy of each photon without filtering. |
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The amount of error allowed in the evaluation. Larger numbers give less accurate evaluations (i.e. smaller areas of the map will be scanned), while smaller number will result in larger areas of the map being scanned. Render time goes up as the error tolerance goes down. Default |
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Specifies the "filter" for computing the irradiance from photons. When evaluating photon contributions, the incoming radiance is divided by the area that the photons cover (to determine the flux). The area can be computed in three different fashions:
The minimum bounding sphere of all photons will be used to estimate the area. This estimator will result in soft blobby looking photon evaluation. It can be inaccurate near edges of primitives.
Like sphere, but uses the volume of the minimum bounding sphere rather than area to normalize photon tracing results. When using volume filtering it is usually necessary to divide the photon lookup result by the volume density to correct for the density-weighted photon distribution that occurs in volumes. When using volume filtering, the normal passed to the
Use the convex hull of all photons is to estimate the area. This estimator will result in slightly "sharper" edges in the photon evaluation, and can be more accurate near edges of primitives. However, since there are sharper edges, this estimator can produce very noisy evaluations.
This filter should be used for photon maps that have been pre-filtered (for example, for maps that have already been filtered by the pcfilter utility). It will cause the photon energies to be averaged without area estimation. |
Examples
Cf = photonmap(map, P, normalize(frontface(N, I)), "nphotons", 100, "type", "diffuse", "error", 0.05, "filter", "convex);
vector clr; float area; photonmap(map, P, normalize(frontface(N, I)), clr, area, "nphotons", 100, "type", "diffuse", "error", 0.05, "filter", "convex); Cf = clr;
| photon | |
| ptcloud |
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| texture |