Print a warning when doing multipass rendering but pixel decorrelation is off

[dictoon]

Multipass rendering is a technique that does multiple passes over the whole image, with each pass adding a fixed number of samples to every pixel.

The two other techniques are single-pass rendering, where a fixed number of samples is computed at once for every pixel, and progressive rendering where samples are added "randomly" across the entire image plane, allowing to have a quick overview of the entire image before convergence is achieved.

When doing multipass rendering, the Decorrelate Pixels option must be enabled. In fact, in the user interface, Decorrelate Pixels is automatically checked (and grayed out) when the number of pass is greater than 1:

However, a hand-edited project file or one that was generated by an exporter may have Decorrelate Pixels disabled even though multipass rendering is enabled. The goal here is to detect this configuration and print a warning message when rendering starts.

Unfortunately, it appears not to be easy to do it cleanly.

The problem is the following: the number of pass (which triggers multipass rendering when that number is > 1) is a parameter of the "generic_frame_renderer" component:

<parameters name="generic_frame_renderer">
    <parameter name="passes" value="1" />
</parameters>

while the Decorrelate Pixels flag is a parameter of the "uniform pixel renderer" component:

<parameters name="uniform_pixel_renderer">
    <parameter name="decorrelate_pixels" value="true" />
</parameters>

By default, these two components can't see each other's parameters.

The obvious solution is to copy the number of rendering passes to the uniform pixel renderer's parameters. We already do this kind of things occasionally: https://github.com/appleseedhq/appleseed/blob/5c83ad129968e2807de0a33e90fe056e517e7aef/src/appleseed/renderer/kernel/rendering/masterrenderer.cpp#L623

[camargo]

Has anyone been working on this? If not I'll give it a shot.

[EDIT] Will be working on this after finals next week. [EDIT] Done with finals. Working on this now.

[dictoon]

Not that I know, you can go ahead!

On Thursday, March 13, 2014, Chris notifications@github.com wrote:

Has anyone been working on this? If not I'll give it a shot

Reply to this email directly or view it on GitHubhttps://github.com/appleseedhq/appleseed/issues/316#issuecomment-37593249 .

[garvitverma]

Is anyone working on this one ? can i give it a shot?

On Fri, Mar 14, 2014 at 3:42 AM, François Beaune notifications@github.comwrote:

Not that I know, you can go ahead!

On Thursday, March 13, 2014, Chris notifications@github.com wrote:

Has anyone been working on this? If not I'll give it a shot

Reply to this email directly or view it on GitHub< https://github.com/appleseedhq/appleseed/issues/316#issuecomment-37593249>

.

Reply to this email directly or view it on GitHubhttps://github.com/appleseedhq/appleseed/issues/316#issuecomment-37593447 .

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Regards, Garvit Verma BITS PILANI-K.K. Birla Goa Campus M.Sc(Tech.) Information Systems President,Computer Graphics Club Autodesk Student Expert

[dictoon]

Chris is already on it.

[dictoon]

Done.