On 2/7/19 4:34 PM, clipka wrote:
> Am 07.02.2019 um 17:31 schrieb William F Pokorny:
> 
...
> 
> Let's play a game of "shapes that could benefit from internal bounding 
> but don't have any" ;)

On doing the solver work I'm - a while now - very aware of the internal 
bounding issues with the sphere_sweep(1). However, if memory serves, 
what Lanuhum had was hundreds of thousands of short sphere_sweeps/hairs. 
Why would this be so much slower than one, or several, equally screen 
filling ones, if bounding is working well(2). A possible answer is the 
inside test on setting up original rays is for some reason doing the 
test on all the hairs.

(1) - I've made a changes to the inside test of the sphere_sweep as 
currently updated for my solver changes. Specifically a change to break 
out of the test loop on the first segment where the point tests inside 
true. Today the test runs through all the segments no matter. It's not a 
change necessary for the solver changes - just something I noticed.

(2) - His textures looked to be simple.

> 
...
> 
> Just a spontaneous thought here: Would it be worth it to cache the 
> result of the camera ray origin inside test, and only re-do it if the 
> origin changes (due to special camera or focal blur)?
> 

Maybe, yes. Globally turning the inside testing off when it's not 
necessary perhaps another idea, but that would add some bookkeeping to 
the parser.

> 
...
> 
> I'm not so sure it's a CSG thing you're seeing. By default, POV-Ray 
> "flattens" CSG unions wherever possible, promoting all children to 
> top-level objects - presumably this is also the case with implicit 
> unions like the text primitive. So unless you took some measure to 
> specifically prevent this, you're not actually testing a CSG object.

Agree. It's a theory until proven.

Will say, a reason I chose the shipped ttf1.pov for the AA and not-AA 
testing is there are just two top level text objects in that scene. If 
any text objects will hierarchically flatten into the prime/top level 
seems like those would.

Do you know offhand what sorts of measures prevent flattening? Merge 
pops to mind as suppose we'd need to remember the grouping there. The 
two ttf1 text objects are textured and transformed - things almost 
always the case with the text /csg - but that's it.

Another test which could be done pretty quickly, I guess, would be to 
hack the code to eliminate the inside test on ray initialization for 
ttf1.pov testing as it really isn't needed in that scene. I might try 
that later today as I'm now curious. But, I'm off to do some other stuff 
at the moment.

Bill P.

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