The solution is commonly known as 'ZFail method' or 'Carmacks reverse'. It's the slower method of doing stencil shadows but it's more robust & accurate.
Also, there are problems you'll come across where the near & far clip planes (camera Near & Far settings) can clip your mesh volumes. If you use the ZFail method, there is an easier solution to that also (infinite far clip plane)
Check google for many explanations.
There are still isues with doing stencils, I'm hoping BRL will do something about it, info here:
http://www.blitzbasic.com/Community/posts.php?topic=59602
Please, if you think this is a good idea (hell yeh! :) then drop a post supporting it :)
While I have your attention, here is my latest DLL. I've made some better functions for doing renderstates because SetRenderState is too much typing :)
http://www.tomspeed.com/dx7dll/
Some things you should know:
Blitz3D, as of v1.96, doesn't specifically create a stencil capable ZBuffer. Out of pure luck, NVidia always seems to create one, ATI cards don't. (This is why the old DeviceClear never worked correctly with the +4 flag)
Skidracer has said he'd look into changing this so Blitz3D always creates one if possible. Until then, you can check for the stencil buffer depth, and create a new one if neccessary, like so:
DeviceClear() now works correctly when clearing the stencil buffer if you create one yourself on ATI cards, and it no longer takes a RECT Type in the parameters:
Example, clear color to red, zbuffer to 1.0, stencil to 0
Const COLBUFF=1
Const ZBUFF=2
Const STENBUFF=4
DeviceClear COLBUFF+ZBUFF+STENBUFF,$ff0000,1.0,0
Before using any of the functions in the DLL you need to initilize it like so:
Here are some of the new functions, much easier to use! Check the .decls file for others.
Also, there are problems you'll come across where the near & far clip planes (camera Near & Far settings) can clip your mesh volumes. If you use the ZFail method, there is an easier solution to that also (infinite far clip plane)
Check google for many explanations.
There are still isues with doing stencils, I'm hoping BRL will do something about it, info here:
http://www.blitzbasic.com/Community/posts.php?topic=59602
Please, if you think this is a good idea (hell yeh! :) then drop a post supporting it :)
While I have your attention, here is my latest DLL. I've made some better functions for doing renderstates because SetRenderState is too much typing :)
http://www.tomspeed.com/dx7dll/
Some things you should know:
Blitz3D, as of v1.96, doesn't specifically create a stencil capable ZBuffer. Out of pure luck, NVidia always seems to create one, ATI cards don't. (This is why the old DeviceClear never worked correctly with the +4 flag)
Skidracer has said he'd look into changing this so Blitz3D always creates one if possible. Until then, you can check for the stencil buffer depth, and create a new one if neccessary, like so:
;We need a stencil buffer greater than 1bit (idealy 8bits) to do a viable Carmacks Reverse If GetStencilBitDepth() < 8 CreateStencilBuffer() If GetStencilBitDepth() < 8 RuntimeError "Card does not support >1bit Stencil Buffers" End If
DeviceClear() now works correctly when clearing the stencil buffer if you create one yourself on ATI cards, and it no longer takes a RECT Type in the parameters:
Example, clear color to red, zbuffer to 1.0, stencil to 0
Const COLBUFF=1
Const ZBUFF=2
Const STENBUFF=4
DeviceClear COLBUFF+ZBUFF+STENBUFF,$ff0000,1.0,0
Before using any of the functions in the DLL you need to initilize it like so:
;---------------- ;Init the DX7 DLL ;---------------- DX_D3D=SystemProperty$("Direct3D7") DX_DEV7=SystemProperty$("Direct3DDevice7") DX_DRAW7=SystemProperty$("DirectDraw7") DX_HWND=SystemProperty$("AppHWND") DX_INSTANCE=SystemProperty$("AppHINSTANCE") If SetSystemProperties(dx_d3d,dx_dev7,dx_draw7,dx_hwnd,dx_instance) RuntimeError "Error with 1 or more SystemProperty vars"
Here are some of the new functions, much easier to use! Check the .decls file for others.
;D3DSTENCILOP Const SOP_KEEP = 1 Const SOP_ZERO = 2 Const SOP_REPLACE = 3 Const SOP_INCRSAT = 4 Const SOP_DECRSAT = 5 Const SOP_INVERT = 6 Const SOP_INCR = 7 Const SOP_DECR = 8 ;D3DCMPFUNC Const CMP_NEVER = 1 Const CMP_LESS = 2 Const CMP_EQUAL = 3 Const CMP_LESSEQUAL = 4 Const CMP_GREATER = 5 Const CMP_NOTEQUAL = 6 Const CMP_GREATEREQUAL = 7 Const CMP_ALWAYS = 8 EnableStencil DisableStencil SetStencilFunc CMP SetStencilPass SOP SetStencilFail SOP SetStencilZFail SOP SetStencilRef VAL# ;... ;Note, these do work, but RenderWorld() overrides their ;settings :| I'm hoping BRL will fix this behaviour as ;they're crucial to implementing good stencil shadows! EnableZBuffer DisableZBuffer EnableZWrites DisableZWrites EnableAlphaBlending DisableAlphaBlending