#PAR card & shadow proble
4 messages in this thread
Martin wasn't referring to the size of the material map, but to the
size of the SHADOW map that the shadow-casting light(s) is(are)
using. Try using Lights/Spot/Adjust and picking your spot, then
selecting the Cast Shadows Adjust button to get to the Local Shadow
Control dialog. There you'll see settings for shadow map size, bias
and sample range.
Dave: So if I understand you correctly, I shouldnt necessarily shy away from a
really Grassy looking material.. just check the size of the shadow map ?
<< to get to the Local Shadow Control dialog. >> << There you'll see settings
for shadow map size, bias and sample range. >> I've always left them at the
defaults with global settings.. I played around a bit with the numbers for map
bias, map range and map sample range but even with only one frame rendered I
could see the circular pattern in the aerial view so I guess it's back to
changing the material for plain green…
Robert:
Yes, use as grassy a material as you like.
Regardless of whether you want to use the Global Shadow parms or the Local,
"because [shadow maps] are made of up of bitmaps, the resolution [shadow map
size] you use for each shadow-casting bitmap inversely affects the accuracy of
the shadow and the rendering time. Thus, the higher the resolution, the more
accurate the shadow, but the slower the rendering time." – page 7-160
"Map size – Used for shadow maps only, this sets the size, in pixels-squared,
of the shadow depth bitmap. The map size requirements depend primarily upon
the DISTANCE of the light source to the object, and secondarily upon the
rendering output resolution. If the shadow map appears too coarse, increase
the map size. The bitmap used by the shadow maps must fill the area covered by
the falloff of the spotlight. Thus, the wider the falloff, the coarser the
shadow appears." – page 7-162
"Map Sample Range – Used for shadow maps only, the Sample Range determines how
much area within the shadow is averaged. This affects the size of the soft
edge of the shadow and is roughly similar to the falloff of a spotlight. Small
values reduce the area that is averaged, effectively bringing the edge of the
shadow inward, which produces sharp-edged shaodws with more aliasing. There
are three basic situations to watch out for: Values less than 3 can produce
coarse-edged shadows, which you can offset by increasing the Map Size. Values
greater than 5 can produce streaking and moire patterns, and require increased
Bias values or a larger Map Size." – page 7-163
Another thing not _directly_ mentioned, is the fact that the greater the number
of objects/faces in the scene (ie that the light can see) the worse the shadow
will look. In fact, with a too small map size, shadows of smaller objects can
disappear entirely because they are essentially spread too thin!
So, make the map size as large as you can (but remember that , say, a 3500 line
map takes something like 50Mb of RAM), and keep the sample range low. Make the
spotlight as close to the objects it's illuminating as possible, and you may
need to use an array of overlapping lights to get broader coverage at a closer
range. In this case, each shadow map can be smaller, as it "sees" less.
Dave
David, thanks for the suggestions on Shadows… I'll be working on them this
weekend and will let you know how it went in a day or so.. for this project I
kept it at one spotlite kept high in the sky and the effect from a distance was
a soft shadow.. must admit that changing the ground material to matt green
instead of grass immediately got rid of moire pattern and the whole effect is
nicer.. now to figure how to get trees and other "real" items to be placed
around the building.. Bob