OpenGL-problems

[KeesW]

Here is a strange happening. We're generating an axonometric of a large house. Works fine with the internal engine but with OpenGL, a couple of the roof slabs are missing and so is a portion of the floor. Is this likely to be an OpenGL bug, or a video card problem?

Also, a chap in our drawing office uses Revit. This has apparently been otimised for OpenGL and he says that it shows shadows. I was told that OpenGL has limitations and one of them is that it won't show shadows. Is that right? Or is this a (poor) Graphisoft implementation of OpenGL?

OpenGL default images are very dark. Is that normal?

Cornelis (Kees) Wegman
AC10, Windows XP Pro, 1GB RAM, NVidea FX 5200, 40GB HD (lots of space left on it)

[andrewzarb]

Open Gl is a great language, just look at what games like Quake can do with it; transparency, reflections, shadows, lighting...

I remember playing on a SiliconGraphics Indigo in 1995, anyone remember those? Silicon Graphics wrote Open GL and their machines back then could show stuff ArchiCAD users only dream about.

[KeesW]

I have loaded Archicad 10 on a new home computer. Same problems with open-GL exist - ie some roofs not showing. Transparency settings are OK and occlusion I can't find. Reducing the size of the 3D window doesn't help. Roofs and slabs show correctly with internal 3D engine.

Both graphic cards are NVidea.

Strangly enough, changing the material does fix it. Settings of all roofs seem the same but new paramenters have been added in the floor plan and section parameter box of elements. Guess I'll just keep looking.

[Ralph Wessel]

Dwight wrote:
Ooops.
Yes, OpenGL can do transparency, shadows - the works.

OpenGL can render shadows, but it doesn't calculate them for you, i.e. it isn't as easy as just flicking a switch to turn on the shadows in OpenGL. ArchiCAD models can quickly generate a lot of polygons, and the time required to calculate shadows cast from them might be excessive. Consider the time ArchiCAD takes to calculate cast shadows for a section/elevation view.

Games shouldn't be compared to CAD because game engines and graphics are designed to work within a very narrow (highly optimised) context. I'm sure we will see shadows in ArchiCAD's 3D window at some time in the future though.

BTW, I've also seen roofs randomly disappearing in the 3D and/or section windows. They usually reappear if I edit the object in any way (or slightly move the section line. I haven't confirmed it yet, but it's my impression that it is usually roofs with a skylight inserted.

[Dwight]

Fair enough. But who cares if it takes a while to generate shadows? The advantages of an OpenGL shortcut to PhotoRendering are numerous.

If Archicad users could generate a shadow-casting OpenGL view with surface textures and window transparency, those features would represent a substantial quality improvement in design communication because:
1: OpenGL exists because it is fast(er), even when imaging shadows, and especially for fly-thrus where photoreal quality is always diminished and movement emphasized.
2: Almost all design decisions could be more attractively and more quickly shown - the lesson of SketchUp is that a pastel cartoon rendering like it makes is as good as a wink to a blind man.
3: The superficial nature of OpenGl helps disguise incomplete models - at a time when design decisions get made....