Im having a bit of trouble when it comes to my z-buffer, i know that this is the problem because of similar topics and websites i have found. Any of the topics I have found are either c++ or open gl related, some of the commands are easy to translate to the C# and MDX but others are not and i was wondering if someone can help... -------------- from what i have found most topics seem to say its the renderstate.. z depth write on, z depth write on, source alpha test - render when 255 (opaque) z depth write off, z depth test on, source alpha test - render when < 255 other source... pd3dDevice->SetRenderState( D3DRS_ALPHATESTENABLE, true ); pd3dDevice->SetRenderState( D3DRS_ALPHAREF, 0x01 ); pd3dDevice->SetRenderState( D3DRS_ALPHAFUNC, D3DCMP_GREATEREQUAL ); -------------- this might be wrong but i translated the above c++ code into... device.RenderState.AlphaBlendEnable = true; device.RenderState.ZBufferFunction = Compare.GreaterEqual; but i cant find how to do the alpha ref, Any help would be excellent, -Dave [Edited by - REspawn on September 5, 2006 7:04:18 PM]

device.RenderState.ZBufferFunction = Compare.GreaterEqual;

Generally, Never change the z buffer function. It can cause all sorts of havok which is hard to explain. The default is greater equal, leave it that way :-)
If you want to turn off depth writing, set ZBufferWriteEnable to false.

0x01 is 1.

so...

device.RenderState.ReferenceAlpha = 1;

AlphaFunction = Less, etc.

enable Alpha testing with AlphaTestEnable.

Quote:
z depth write on, z depth write on, source alpha test - render when 255 (opaque)
z depth write off, z depth test on, source alpha test - render when < 255

sortof...

z depth write on, source alpha test - render when >= 225
z depth write off, blending on, source alpha test - render when < 225

is about right :-)

225 is probably about right alpha test. Otherwise you won't get much solid shrubbery. :-)

So for pass 1:

No blending,

device.RenderState.AlphaTestEnable = true;
device.RenderState.AlphaBlendEnable = false;
device.RenderState.AlphaFunction = Compare.GreaterEqual;
device.RenderState.ReferenceAlpha = 225;

This will render the majority of the bush as solid, with depth being written to occlude other geometry.

pass 2:
also set the blend mode to pre-modulated alpha (help stop those black edgse on the grass)

device.RenderState.AlphaTestEnable = true;
device.RenderState.AlphaBlendEnable = true;

device.RenderState.SourceBlend = Blend.One;
device.RenderState.DestinationBlend = Blend.InvSourceAlpha;

device.RenderState.AlphaFunction = Compare.Less;
device.RenderState.ReferenceAlpha = 225;


This will draw transparent geometry at the edges that does not write to z, so will not get the errors you are currently seeing.