render problem?

clemens · Post by **clemens** » Sun May 24, 2009 7:36 am

hello,

i have built a simple scene with a flat plane and some boxes.
the boxes are controlled via a physics engine (pal with bullet).
when they fall to the ground, some of these boxes start to flicker - even
when they are motionless. in my example there are 500 boxes and approx.
10-20 boxes are flickering. and there is just another effect: if i look around
with the camera controlled with the mouse, often the boxes at the screen-borders start to flicker or just disappear. this effect is less if i set the gravity
from 10 to 1, so that all action is very slow. may this be a rendering issue?

regards,
clemens

hybrid · Post by **hybrid** » Sun May 24, 2009 9:33 pm

Maybe the boxes have zbuffer issues, which lead to flickering due to minimal gravity movements?

clemens · Post by **clemens** » Tue Jun 23, 2009 2:25 pm

if this is a zbuffer problem, how to solve? i have set up the
graphics device with 32 bits instead of 16 - same issue.

i have changed the physics engine from bullet to newton - same issue.

i have disabled pal and worked directly with bullet to see if its a pal problem - boxes still start to flicker.

what i can see is, that if i turn the camera around a flickering box it stops this behavior sometimes when i change the way i look at it. if it is located in the center of my view it disappears - if it is located under the center it is visible. i can repeat this endless for this object.

is this maybe due to the camera-viewmatrix? i have already tried to change the near-far clipping plane with no result. maybe the aspect-ratio?
any hints?

Acki · Post by **Acki** » Tue Jun 23, 2009 2:53 pm

maybe a culling problem (node->setAutomaticCulling) ???
but this shouldn't if the box is in the center of the screen, except if it's a bounding box problem (try node->setDebugDataVisible)...

if nothing works, make a download or post code that reproduces the error so we can check it...

christianclavet · Post by **christianclavet** » Tue Jun 23, 2009 3:28 pm

I don't know much things with physic engines, but have you checked this?:

- Pausing the simulation, to see if the physic engine was not forgetting some objects from frame to frame.

- Tryied with variants of the number of boxes (start with 10, 20, 30, and so on)

- Checked when the RENDER is done from the physic engine, could be out of sync with the IRRlicht begin scene and endscene commands.

Culling distance would be a good thing to check also as mentionned by Acki.

clemens · Post by **clemens** » Tue Jun 23, 2009 9:04 pm

ok. i tried the following proposals from Acki and Christian (thanks!):

-changed the number of boxes - flickering/disappearing starts approx. > 70 boxes

-same thing if i stop physics calculation/updating box-position/rotation

-tried out node->setAutomaticCulling() with EAC_OFF, EAC_BOX and EAC_FRUSTUM_BOX - but its always the same effect

so this is not due to the physics engine, i think. but i have seen another interesting thing: at program start i place all boxes at a grid position and stack some layers of 7x7 boxes so that i have 7x7x e.g.10 = 749 boxes. they are floating in the air until the application starts and the physics engine adds the gravity. if i stop physics, so that the boxes stand still - there is no flickering except at the screen-borders. if i turn around, i can see this effect always at the borders - lines of boxes disappear at once. if i let all boxes fall to the ground so that they are cluttered, this effect can be seen everywhere on the screen - not just at the borders.

by the way, this happens in opengl- and also directx-mode.

which issues do i have to look for if i set the setDebugDataVisible-method? maybe there are some useful informations - as Acki suggested?

Acki · Post by **Acki** » Tue Jun 23, 2009 10:09 pm

clemens wrote:which issues do i have to look for if i set the setDebugDataVisible-method? maybe there are some useful informations - as Acki suggested?

mainly I thought using it to check if the bounding boxes are correct (for culling)...

belfegor · Post by **belfegor** » Wed Jun 24, 2009 11:49 am

Maybe its problem with your "placement" code for boxes, so one box is overlaping other that can cause flickering?

clemens · Post by **clemens** » Wed Jun 24, 2009 7:23 pm

i 've got it!

until now i have created all objects with mSmgr->addOctTreeSceneNode() because the code documentation says "a good method for rendering scenes with lots of geometry".

i simply replaced this by mSmgr->addMeshSceneNode() - and the flickering is gone! ! !

i go now and play a bit with stacks...

thank you all for your proposals! good to know that people offer help here.

Irrlicht Engine

render problem?

render problem?

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