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wildeyedboyfromfreecloud
02-23-2002, 01:17 PM
is there anyway to do say like volumetric shadowing with an infinite volume of a projected texture. like the shadow volume created by a stain glass window. even without the stencil. just a blended projection of texture. so technically it isn't a shadow and is basically a 3d texture. so is it sensible to do 3D textures without raytracing? i get the impression from my 3d graphics text book it isn't.just curious. its also important to me because i want to use procedural 3d textures for a lot of other applications. thanks

michael

[This message has been edited by wildeyedboyfromfreecloud (edited 02-23-2002).]

dorbie
02-23-2002, 10:17 PM
Well a stain glass window is not a good example. It's easy and is really only 2D unless you interject an occulter, in which case you have a projective light source with your choice of conventional shadow modulation.

If it's the volumetric illumination of dust in the air, some work has been done. There are Siggraph paoers on illuminated volumetrics which are quite fast and don't raytrace at least for the rendering phase. Billboarded cloud 'particles' like a splatting system using textured polygons was the kind of approach used I think.


[This message has been edited by dorbie (edited 02-24-2002).]

wildeyedboyfromfreecloud
02-24-2002, 09:17 AM
for give my ignorance but what is an occulter... 1.) the state of being hidden from view or lost to notice. 2.) the shutting of of the light of ine clestial bodyhe intervention of another.
i don't follow. say a light illuminates a stainglass window. then the light penetrating the glass would creat a volumetric "iluminated shadow" or i suppose if there were dust particles in the air for light to refract of of. and then would be typically cast as a shadow. i pretend to understand the stencil buffer. i hypothesize that it interacts with the depth buffer to determine what to cut out. is it possible to project a textured shadow or is it only possible to create a flat shadow. which i would bet is the case. again for give my ignorance but there is GL_TEXTURE_2D mode but i find no support for a GL_TEXTURE_3D mode.

i guess the dust would be particles or no? and entail some light scattering effects? oh nm you said that, may i ask what billobarding is. i've seen the term around... but anyhow where can one find sigraph papers again?

btw if the stain glass is easy could you drop me a clue. would you have to project it and clip it to the intersecting surfaces? or is there an easier way?


[This message has been edited by wildeyedboyfromfreecloud (edited 02-24-2002).]

i'm also intereted in using procedural 3d textures for creating marble, wood, geological or organic nextures. and what not would it be computationally inneficient to do so or no? and could you convert a 3d texture to a 2d texture once the surface textures are determined if that owuld speed up processing.

[This message has been edited by wildeyedboyfromfreecloud (edited 02-24-2002).]