strange problem with LWJGL Xith3D renderer

[willdenniss]

I'm seeing some strange issues with the LWJGL port of the renderer for Xith3D.

This image is meant to be a cube:


It should look like this:


Any ideas?

It looks like we've got something reversed???  The outline of the cube is correct.

Will.

[elias]

Looks like someone forgot to ask for depth buffer bits.

- elias

[cfmdobbie]

Things that could be causing that:

• No depth buffer bits requested
  
• Depth test not turned on
  
• Depth test has incorrect function selected
  
• Polygon winding order of vertices incorrect
  
• Vertices specified in wrong order
  
• Incorrect face culling
  
• Vertices put into buffer in wrong order

I seem to recall some craziness with winding order in Xith3D - can't quite remember though...

[willdenniss]

Thanks!  It was the depth bits.

I'm glad it wasn't the other options, I had hoped something so major would not have changed since your initial port.

It was fixed by changing the call to Display.create() to:

Display.create(new PixelFormat(0, 16, 0));

I read this thread: http://lwjgl.org/forum/viewtopic.php?t=656&highlight=depth+buffer+bits (which referenced this one: http://www.gamedev.net/community/forums/topic.asp?topic_id=258086) for details on how to accomplish this.

Some further questions:

[list=1]

• Is it always nessesary to specify a custom PixelFormat?
  
• What is the default behaviour (can't seem to see any mention of it in the docs).  
  
• If by default the depth bits are set, is this a bug in the OSX port?  
  
• If by default the depth bits are not set - what use is that method (wouldn't everyone need the depth bits set?)?
  
• Should I set the other pixel format bits for alpha and stencil?
  
• Do most people have unique pixel format requirements or is there a common configuration?
  [/list:o]
  
  Thanks for your help.
  
  Will.

[elias]

[list=1]

• Is it always nessesary to specify a custom PixelFormat?
  
• What is the default behaviour (can't seem to see any mention of it in the docs).  
  [/list:o]
  

Yes, if you want to specify minimum pixel caps. The defaults are no requirements (0 as a,d,s bit depths).

[list=1]

• If by default the depth bits are set, is this a bug in the OSX port?  
  
• If by default the depth bits are not set - what use is that method (wouldn't everyone need the depth bits set?)?
  [/list:o]
  

There's probably not a bug in the OSX port. More likely, the particular OpenGL driver you have chooses to give you no depth since you (indirectly through the defaults) specified 0 bit depth as requiment.

[list=1]

• Should I set the other pixel format bits for alpha and stencil?
  
• Do most people have unique pixel format requirements or is there a common configuration?
  [/list:o]
  

Yes, if you need them. Most people need some sort of depth buffer, but it's varies whether the alpha and stencil bits are needed.

- elias

[elias]

I've just committed a change that makes the default no-arg PixelFormat constructor specify a minimum of 8 bits depth buffer.

- elias

[willdenniss]

I've just committed a change that makes the default no-arg PixelFormat constructor specify a minimum of 8 bits depth buffer.

- elias

Thanks for your answers and the change.

It might be helpful to mention the PixelFormat stuff in the docs for create().

Will.

[princec]

It would indeed be a good idea if we went through all the Javadoc comments and made sure they were very comprehensive. We're perilously close to 1.0 now.

Cas