Stencil buffer does not work [It does! stencil shadows soon]

treeform · May 31, 2007, 2:52am

Stencil buffer does not work can you spot my problem? It should only render when panda hits the card.

import direct.directbase.DirectStart
from pandac.PandaModules import loadPrcFileData
from pandac.PandaModules import NodePath,CardMaker,StencilAttrib
loadPrcFileData("", """
framebuffer-stencil 1
""")
messenger.toggleVerbose()
cm = CardMaker("cardmaker")
readerOnlyIfOne = StencilAttrib.make(1,StencilAttrib.SCFEqual,StencilAttrib.SOKeep,StencilAttrib.SOKeep,StencilAttrib.SOKeep,0,1,0)
dontRenderPutOne = StencilAttrib.make(1,StencilAttrib.SCFAlways,StencilAttrib.SOZero,StencilAttrib.SOReplace,StencilAttrib.SOReplace,1,0,1)
cm.setFrame(-15.5,15.5,-5.5,35.5)
viewingSquare = render.attachNewNode(cm.generate())
viewingSquare.node().setAttrib(dontRenderPutOne)
view = loader.loadModel("panda")
view.setScale(3)
view.node().setAttrib(readerOnlyIfOne)
view.reparentTo(render)
render.analyze()
run()

I will write you some stencil shadows as soon as i figure out how panda uses the stencil buffer.

ynjh_jo · May 31, 2007, 4:25pm

You should change the config before importing DirectStart.
I’m looking forward for your stencil shadow.

treeform · June 27, 2007, 5:09am

thanks it works now and need to finish the rest of the shadow

its works even better if you set the stencil stuff to transparent even though it is not showing. I guess it effects draw order better then my manual sorting … which does not do any thing

treeform · July 14, 2007, 9:31pm

i made all i could on the stencil shadows. The artifact you see in the image is done by not enough stencil bits. Although i have asked for 8:


from pandac.PandaModules import loadPrcFileData
loadPrcFileData("", """
framebuffer-stencil 1
stencil-bits 8
""")

it still does not give them. It gives me only 1 or 0 bits. Is there any way around this problem as soon as i get the panda compiled i will try to find where the stencil source is.

thanks for all your input!

ynjh_jo · July 15, 2007, 5:12am

Great progress !

this is what I got :
I already have 8 bits stencil buffer, even without asking for it :

fbProp=base.win.getFbProperties()
print 'accumulation bits:',fbProp.getAccumBits()
print 'alpha bits:',fbProp.getAlphaBits()
print 'color bits:',fbProp.getColorBits()
print 'depth bits:',fbProp.getDepthBits()
print 'stencil bits:',fbProp.getStencilBits()

treeform · July 15, 2007, 4:30pm

the error was in my algorithms! Now fixed! I will clean up and speed up the code and post it soon.

stay tuned!

ynjh_jo · July 15, 2007, 7:15pm

as I guessed, it must be your shader.
that’s GREAT, and would be GREATER if included in 1.4.0 shipment.

treeform · July 15, 2007, 7:28pm

it uses no shaders. Its the 1980s shadow tech that is now becoming popular again with engines like doom and half life.

It still very slow and would have to be recoded in C++ for sure. When is the 1.4.0 shipment?

ynjh_jo · July 16, 2007, 3:20am

I know what it is.

How do you build the edges and extrude it ? iterating through the vertex data in Python ?
I would do that since I don’t have any C/C++ exp. That’s what keep me away from it.

this is a cool thing from McCool :

Shadow Volume Reconstruction from Depth Maps
Michael D. McCool
University of Waterloo

Current graphics hardware can be used to generate shadows using either the shadow volume or shadow map technique. However, the shadow volume technique requires access to a representation of the scene as a polygonal model, and handling the near plane clip correctly and efficiently is difficult; conversely, accurate shadow maps require high-precision texture map data representations, but these are not widely supported.

We present a hybrid of the shadow map and shadow volume approaches which does not have these difficulties, and leverages high-performance polygon rendering. The scene is rendered from the point of view of the light source and a sampled depth map is recovered. Edge detection and a template-based reconstruction technique are used to generate a global shadow volume boundary surface, after which the pixels in shadow can be marked using only a ONE bit stencil buffer and a single-pass rendering of the shadow volume boundary polygons. The simple form of our templatebased reconstruction scheme simplifies capping the shadow volume after the near plane clip.

rdb · July 16, 2007, 7:53am

This is awesome work Treeform!
I’m currently using the shadow algorithm that is also going to be included in 1.4.0 - but I achieve very pixely shadows there. I’m looking forward to see this shadow working in my program!

Oh, and a question: can your method also project shadows on different objects than just a plane?

ynjh_jo · July 16, 2007, 11:30am

pro-rsoft, wikipedia always a great place to start :
en.wikipedia.org/wiki/Shadow_volume

treeform · July 16, 2007, 12:44pm

pro-rsoft: yes it shadowed itself in the image. There is not real “lights” or shades in the scene. Yes iterating in python and making a new 3d shadow solid is the major slow down. But it can be used to generate a solid for say a game level once during startup.