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Postlight

15 February 2007 87,607 views 3 Comments

Post Light settings

This page will take you through each of the numerous settings of Post Light.


Light Wildcard

Post Light uses this wildcard to select which lights are used in the Post Light render.

So for example, if the wildcard is set to *_Bright, any light ending in _Bright will be used, e.g. Point_Bright, Kicker_Bright, etc.

Area Light Jitter

Describes how much randomness is applied to the rendering of area lights.

Low values will often produce banding in shadow outlines, while higher values will produce noisy results. Allowed range is from 0 to 1.

Use Scene Ambient

Enable this to use the current scene settings for ambient illumination in your Post Light render.

Use View Visibility

If this setting is enabled, then any lights which are hidden in the scene will not be used in the Post Light render.

Use Render Visibility

If this setting is enabled, then any lights which are set to not appear in the Mental Ray render will also not be used in the Post Light render.


Use Shadows

Enable this setting to tell Post Light to render shadows.

Area Light Shadows

If this setting is enabled, Post Light will render soft shadows for any area light, otherwise Post Light will render a hard edged shadow.

Be warned that soft area light shadows always take much longer to render. If you decide to use soft area light shadows, you’ll probably need to use the Post Light cache system (described later).

Shadow Wildcard

Use the shadow wildcard to specify which objects to use to cast shadows. The default value of *_POSTSHADOW means that any objects in your scene whose name ends with _POSTSHADOW will be used to cast shadows in the Post Light render.

You should always use a separate polygon object to cast shadows as an approximation to any high resolution objects in your scene. To keep things fast, try to use as few polygons as possible (less than 1000). If you try to use the same object to cast shadows, then you will have problems with unpredictable self shadowing. Your shadow object should always be contained inside the object it is representing, as otherwise it will cast shadows in the wrong places. You can use the push deform operator to shrink the shadow model appropriately.

Max Octree Leaf Size

Post Light uses an octree to optimise shadow rendering. This is similar in concept to XSI’s BSP tree, and Post Light provides two settings to allow you to tweak the octree construction (again, in a similar manner to XSI).

Max Octree Leaf Size dictates the threshold number of polygons that the octree uses to decide when to subdivide a cell into 8 smaller cells. Making this number smaller means that the tree will be deeper. A tree which is too deep, will ofter be slower than searching through a larger number of polygons.

To get optimum results, use the Log Messages option on the Settings tab of Post Light to write out timing and octree build information that you can use to optimise your octree.

Max Octree Depth

This setting provides a maximum limit on the depth of the octree. Setting this value too small, can result in leaf nodes that contain too many polygons, and can result in longer render times.


Camera Name

This specifies the name of the camera that Post Light uses during its render. This is needed so that specular highlights are rendered in the correct position.


Render Diffuse

Specifies the amount of diffuse lighting to apply to the Post Light render.

You can use this to turn down the amount of diffuse illumination that the lights in the scene apply to the final Post Light render.

I’d generally recommend not to adjust this setting, since there is no corresponding control inside XSI to replicate this for your scene. If you adjust this value, you may end up with results that don’t match your Mental Ray render.

This setting is only provided as a handy way of seeing how the lights are affecting the render with their diffuse illumination.

Render Specular

Specifies the amount of specular lighting to apply to the Post Light render. You can use this to turn down the amount of specular illumination that the lights in the scene apply to the final Post Light render.

As with the Render Diffuse setting, I’d generally recommend you not to adjust this. This setting is only provided as a handy way of seeing how the lights are affecting the render with their specular illumination.

Cache Diffuse

Use this setting to modify the amount of affect that the Cache input has on the diffuse component of the Post Light render.

Cache Specular

Use this setting to modify the amount of affect that the Cache input has on the specular or additive component of the Post Light render.


Cache Mode

This setting tells Post Light to output a specially encoded image that only stores the lighting information, and not the final render.

This specially encoded image is designed to be fed into the Cache input of another Post Light tool. If you try to view the output of Post Light when this setting is enabled, you will most likely just see a black image.

Log Messages

Enabling this will mean that Post Light will write debug information to the Script Editor’s log window.

This debug information includes information about how long Post Light has taken to render the current image, as well as information about the structure of the octree. This information is very useful for optimising your renders when working with shadows.

Toggle to refresh

This is a dummy setting that is used by the Post Light Monitor to automatically refresh Post Light when the lighting in the scene has changed. If you so wish, you can also use it to manually refresh Post Light.

This setting has no affect on the final Post Light render.

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3 Comments »

  • Adam Seeley said:

    Hi, Any idea if this works in Xp 64 bit Soft 2010/2011/2011 sp1.

    Thanks,

    Adam.

  • AndyN (author) said:

    Hi Adam,
    That’s a good question. I can’t see a reason why not, but it would need to be recompiled and I’m afraid I don’t have access to a Windows 64bit machine.

    It could only support phong based lighting models so it didn’t catch on as it probably wasn’t flexible enough for most pipelines. Anyway, as a result, I haven’t kept it up to date.

    Sorry!

  • Moykul said:

    Brilliant tool! Thank you so much!

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