Ways to lower the polys in view?

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CocaCola

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Posted: 1st Sep 2010 03:08 Edited at: 1st Sep 2010 03:08

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OK how would I go about doing this? I have an idea but I wouldn't know how to start coding it, like how would I make it so objects x, y, or z spaces away don't get rendered (Like so when your really far away from a object it pretty much disappears then when you get closer it comes back, so you don't have to use so many polys in big levels)? So it could be a HUGE map, but your only loading so many polys at a time?

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Visigoth

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Posted: 1st Sep 2010 04:44

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you have to keep doing distance checks to the objects. Then, use hide/show object.
Or, you can use LOD.
See the ADD LOD TO OBJECT command.

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CocaCola

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Posted: 1st Sep 2010 04:52

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how do I do distance checks? And if you just hide the object won't it still render the polys?

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Omen

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Posted: 1st Sep 2010 05:13 Edited at: 1st Sep 2010 05:20

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Hiding an object doesn't cause the mesh to render, but it _does_ keep the object in the engine's multi-object loops. Here's one way you could do it...

+ Code Snippet

#constant SYSTEM_VECTOR3_GETDIST 1
r = make vector3(SYSTEM_VECTOR3_GETDIST)

rem let's say your avatar is Object 1 and the object
rem you want to do a distance-based culling check on is Object 2

dist# = systemSharedGetDistance3D(object position x(1),object position y(1),object position z(1),object position x(2),object position y(2),object position z(2))

if dist# > 512
   objectClientHide(2)
   print "The object was hidden"
else
   print "The object was not hidden"
endif


wait key

end

function systemSharedGetDistance3D(x1#,y1#,z1#,x2#,y2#,z2#)

   set vector3 SYSTEM_VECTOR3_GETDIST, (x1# - x2#), (y1# - y2#), (z1# - z2#)
   exitfunction (length vector3(SYSTEM_VECTOR3_GETDIST))

endfunction 0.0

function objectClientHide(mydbpid as integer)
   hide object mydbpid
   exclude object on mydbpid
endfunction

but if you REALLY wan to make your life easy, you'd use 2 cameras: a NEAR camera and a FAR camera. The near camera is used for "details" like grass or building architectural details -- this camera has a very short range, like 60 meters. The far camera has a range that is (for all intents and purposes) infinite (say 20000 meters for example) but the far camera excludes the objects being shown in the near camera. This instantly gives you the same effect of high LOD for items near the camera and low LOD for objects further away with no distance checks required.

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CocaCola

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Posted: 1st Sep 2010 07:03 Edited at: 1st Sep 2010 07:04

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why wouldn't something like this work? (object 1 player, object 2 object you wanna hide)

+ Code Snippet

x=object position x(1)
y=object position y(1)
z=object position z(1)
if object position x(2) = x+1000
     hide object 2
else
     show object 2
endif
if object position y(2) = y+1000
     hide object 2
else
     show object 2
endif
if object position z(2) = z+1000
     hide object 2
else
     show object 2
endif

in the main loop?
So if object 2 is 1000 places away it doesn't show.

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Libervurto

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Posted: 1st Sep 2010 07:33 Edited at: 1st Sep 2010 07:33

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Doing a distance check on every object in the scene is going to kill your frame rate. If you split the scene into a grid then make an array that stores the grid section each object is located in...

+ Code Snippet

remstart
=== Scene Grid ===
0,0  1,0  2,0  3,0
0,1  1,1  2,1  3,1
0,2  1,2  2,2  3,2
0,3  1,3  2,3  3,3
remend

dim objsect([number of objects])

Then you can check which section the object is in and if it's close enough to the camera, draw it. This eliminates the maths used in calculating distances, but there is a quicker way I can think of but wastes a bit of memory: If we make the array based on the sections instead of the objects we can simply check the sections closest to the camera for objects to draw, the memory wastage is because arrays are not dynamic in DB, so we'd have to make each section capable of storing all objects at once. If n is the number of objects and m is the number of sections we'd need n*m array entities, and out of that (n-1)*m would be unused!

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CocaCola

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Posted: 1st Sep 2010 07:39

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Quote: "Doing a distance check on every object in the scene is going to kill your frame rate"

even with

+ Code Snippet

for i=2 to 10000
if object exist i
     if object position x(2) = x+1000
          hide object 2
     else
          show object 2
     endif
endif
next i

????

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Omen

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Posted: 1st Sep 2010 08:44 Edited at: 1st Sep 2010 08:45

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@CocaCola

You really don't want to be doing distance checks against every object every frame. You could use a counter so that you are only doing 1 distance check against 1 object per frame (or more likely totalObjectCount / targetFPS) to go through all objects each second... but eventually it will become a significant hit on framerate as you start adding in more and more objects into the scene (how many clumps of grass will you need for example to have a realistic looking field?).

IMHO, you have to use a combination of tactics... multiple cameras, LOD meshes, splitting up your scene into sections, fog, careful use of the camera distance, even using potential visibility sets to cull entire group of objects (or sections of your map) when they are not visible (for example when behind s-curves) will all help.

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Scraggle

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Posted: 1st Sep 2010 11:49

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You might also want to look at EXCLUDE OBJECT ON, it is more efficient than HIDE OBJECT ... assuming you don't need to perform multi-object checks.

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Quel

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Posted: 1st Sep 2010 13:00

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To be really honest, as far as my experience goes with this distance view topic, the only thing that REALLY does anything to the frame-rate, at least in DBPro, is the stuff VERY close to the camera. (it is very annoying sometimes because ONE single polygon with alpha brings the fps in my case under 10...)

For example i have a complex test scene i've made for developing purposes for my RTS, and once first there was no limit on the 4 corners of it the camera couldn't pass, I went out from the scene, and not so far it was already 60 fps instead of the average 30 (i have a crappy machine...)

I also checked it now, and it was an additional 1 or two frames plus per second when hiding the scene lying in the distance... So why bother at all with this distance thingy, it all just uses more processing power than would be there without it. Of course with VERY big terrains it may not be this simple, but there i guess a simple way of making the level into sections with checking the distances at the array level, and hide or show those is plenty enough.

...or exclude... what it actually does 'Scraggle', i've never heard of that command?

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Scraggle

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Posted: 1st Sep 2010 13:49

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Try this small example:

+ Code Snippet

set display mode 800, 600, 32, 0

for k = 1 to 1000
	make object sphere k, 10
	hide object k
	//exclude object on k
next k

sync rate 0
do
	text 0, 0, "FPS: " + str$( screen FPS())
loop

When you have tried it, make a note of the fps then comment the hide object line and uncomment the exclude object line, then try it again.

On my laptop I get 500 fps with hide object and 1250 fps with exclude object on.

As I understand it, hide object still sends the polygons to the render engine but they don't get rendered. Exclude object on doesn't send the polys anywhere.

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Green Gandalf

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Posted: 2nd Sep 2010 00:39

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Quote: "See the ADD LOD TO OBJECT command."

Thanks Visigoth. I'd missed that one. I wonder if it works on limbed terrains such as Advanced Terrain?

Quote: "Of course with VERY big terrains it may not be this simple, but there i guess a simple way of making the level into sections with checking the distances at the array level, and hide or show those is plenty enough."

That's done automatically for you in the update terrain command for Advanced Terrain.

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CocaCola

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Posted: 2nd Sep 2010 02:09 Edited at: 2nd Sep 2010 02:16

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@scraggle I got better FPS with hide object (200-350 with exculde, 300-450 with hide), and I would something like this be better?

+ Code Snippet

for i=2 to 10000
if object exist i
     if object position x(2) = x+1000
        if hidden(i)=1
          hide object 2
          hidden(i)=1
     else
          show object 2
          hidden(i)=0
     endif
endif
next i

I know that you would have to make a function or something for i but wouldnt that be better?

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Jeff032

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Posted: 2nd Sep 2010 05:43

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Quote: "As I understand it, hide object still sends the polygons to the render engine but they don't get rendered. Exclude object on doesn't send the polys anywhere."

It doesn't seem like the polygons are sent when using hide object. Excluding appears to skip some other calculations.

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Kevin Picone

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Posted: 2nd Sep 2010 05:48

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If you want to reduce the poly's in scene then you need to look into occlusion as per old school tools like Visible Worlds

New PlayBasic Learning Edition Released 24th April 2010

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Green Gandalf

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Posted: 2nd Sep 2010 14:05

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Quote: "@scraggle I got better FPS with hide object (200-350 with exculde, 300-450 with hide), and I would something like this be better?"

Weird. I get the same results as Scraggle:

hide object - 1042
exclude object - 2440.

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James H

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Posted: 2nd Sep 2010 21:04

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I did some tests a long while back that showed using them together gave even better performance. I`m nowhere near my own machine for a week or so, but from what I remember the same tests showed better results for hide vs exclude when there is an excessive polycount. I think that the stress on gpu memory was the reason; I think that perhaps exclusion allows the system to put the object data to one side probably by utilising sytem/graphics shared memory because I carried out the tests on the same gfx card on 2 machines; one with a couple gig ram, and one with shared memory enhancements on the mobo with 4 gig ram; I created so many objects the framrate was down to a few fps on the first machine whereas the second machine showed around 20-30 fps for the same amount of objects. Thought it might be worth mentioning.

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Quel

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Posted: 3rd Sep 2010 22:46

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What kind of beasts are you all sitting in front of, my fps won't go over a hundred with a clear backdrop!

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Quel

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Posted: 3rd Sep 2010 23:03

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I just had the idea of the 'exclude object' command may on the other hand take more time than 'hide object' to do the job. Just a theory, which came up during thinking about what is the sense on having both commands.

If this would be true:
Exclude /include - ideal for example large amounts of stuff to load in at the beginning of the program, and activate when needed.
Hide /show - for things like 'manual' LOD and stuff...

Any thoughts on this? Maybe some other easy little benchmarking snippet could decide... i would write one, but the version of DBP running with me is still a one that doesn't recognize this command.

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