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newbie question about 3d objects and rendering
newbie question about 3d objects and rendering
i am working on a new project involving rendering 3d objects. initially, i did not think about using dwgdirect for doing this, but after brief investigation it seems to have all the features i need. but, i need to confirm whether dwgdirect will be able to do what i need. basically, this is what i'm trying to accomplish. i have data in another application for a 3d model. each model contains an array of surfaces, where each surface is a an array of points. each surface also contains rendering properties such as color. additionally, each surface can contain child surfaces and holes. i would like to feed this data into middleware that i am building using dwgdirect solely for rendering purposes, so that it can display a 3d model that properly shows the surfaces in relation to each other. i don't need to persist anything or allow the user to edit entities while viewing... just displaying, zooming, and rotating using a dolly of sorts. is this something that dwgdirect can do easily? if so, is there an example of how 3d models can be rendered using dwgdirect by importing from a third-party drawing format? i noticed that odamfcapp has an example of reading a 3d dwg drawing and rendering it. but, i know too little about how 3d drawings are structured in dwg files to know how to convert my data to dwg. i would appreciate any help you can provide. thanks.
dwgdirect is mostly intended to work with dwg drawings (read/write/create/edit/view). if your data is in some other format you would need to import it into dwgdirect first (convert to dwg).
depending on format/organization of your 3d data it may be more practical to render it using directx or opengl without dwgdirect.
btw, acis data (sat or sab) can be easily imported into dwgdirect.
sergey slezkin
ok... i've been able to "convert" the data from my third-party application to dwg format by basically creating lines and 3d polylines. so, it draws the edges beautifully using the proper colors. happy so far.
but, when i try to view it with surface shading (e.g. - gourad shading) in the sample mfc application, it doesn't do it properly... it only shows the edges. the "surface" is transparent. why is that? when i create line and 3d polyline objects, do i need to tell it anything more than the points (or vertices) and the color in order to make it render the surface properly?
or, is my only option to use acis? if so, how do i create a acis data (sat or sab)? dwgdirect doesn't seem to have any apis for creating acis data from scratch. can you direct me? thanks.
lines and polylines can't represent a surface. surfaces can be represented by oddbpolygonmesh, oddbpolyfacemesh or acis objects (oddb3dsolid, oddbbody).
oddb3dsolid has a number of methods for creating simple objects (createbox(), createsphere(), ...)
sergey slezkin
you can use a triangulator (for example opengl's triangulator) to convert 3d polylines into 3dface.
do you want obtain a vector or a raster render?
thanks rareba for your suggestion about triangulation. essentially, that's what seems to be missing from dwgdirect for what i'm trying to accomplish. i understand that dwgdirect supports 3dface, but as you mentioned, i need to convert my polyline points into triangles for surface rendering by the 3dface object. ultimately, i'm not to concerned about the rendering engine whether it's directx, gdi, or opengl... whichever performs best. is that what you were asking about rendering raster or vector?
because they are two approach very different. i use opengl triangulator and it is very stable and esy to use. with triangulator you obtain a set of triangles and you can render like you want.
last edited by rareba; 24th january 2007 at 09:28 amfff">.
closed polylines can be used to construct a region (oddbregion).
but the need to be planar.
sergey slezkin