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razor
03-23-2002, 09:40 PM
I'm sorry if my question isn't advanced enough for this forum... but yes i have read the red book, and yes i know openGL, so i hope i'm worthy of your attention http://www.opengl.org/discussion_boards/ubb/smile.gif

Now to the question:

The geForce 3 TI series have something nVidia calls shadow buffers. I have been working on shadows and phong lighting models using a normal plain geForce 3, and i was wondering what exactly these shadow buffers would give me (if anything). Could someone give an overview of why they are better than just using stencil shadows.

Thanks for your time.

davepermen
03-24-2002, 02:12 AM
developer.nvidia.com

i think they explain it good enough themselfes.

short description:
shadowbuffers are simple projected textures wich store distance from lightsource. you compare this distance then against the distance of every pixel you draw and shadow it like that..
pro:fast,simple,even softshadows,only an additional texture, wich has to be rendered first(fast)
constra:artefacts,only spotlights,getting rid of the artefacts is difficult

stencilshadows:
pro:work in every case(pointlights, directionallights),perpixelperfect hard shadows
contra:eating lot of fillrate,implementation more difficult

i dont like the shadowbuffers that much, cause i want omnidirectinal pointlights..

jwatte
03-24-2002, 07:08 AM
Shadow buffers are available on regular GeForce 3, too. In fact, the main thing the GF4 has over GF3 is higher bandwidth; linearly scaled in some areas; massively improved in others. Well, and the GF4MX doesn't have half of the features of a regular GF3, as the 4MX == 2MX+speed bump.

wimmer
03-24-2002, 01:49 PM
Especially the two vertex shaders look attractive. Twice the geometry transformation speed, yummmie http://www.opengl.org/discussion_boards/ubb/smile.gif

Michael