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Issues with Open GL shadows


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In using Open GL render with shadows option I'm getting some strange results in SLVPs. Almost like there are some hidden elements casting shadows on elevation views in these VPs. when traveling back to the DL from the SLVP the odd shadows are gone! I've checked the class/layer overrides for any clues--nothing. Creating a new VP from the DL of the same model, same file yields more odd shadows, only in different places???

I finally found a couple of clues: when zoomed in close on the DL model in elevation view I can see some unwanted shadows cast on a wall with no shadows. This is the really strange part: in this zoomed view if I use the pan (hand) tool, the shadows actually move!(not while panning, but they redraw in a slightly different config after finishing operation) The pan tool does nothing to the model, light, or other objects in the drawing, so how can it change the shadows cast?

Back to the SLVPs. By accident I discovered that the errant shadows disappear if I change the scale of the VP from 1/4" to 1/8". What the heck? How could this be possible? Again, this shouldn't do anything to the model, lighting, VP overrides, other elements etc. Bug?

In the past I've used open GL a lot and I like how it remains rendered when rotating models etc. Now I'm using the Textures and Shadow options in open GL mode so maybe this has been an issue for a while and I wasn't aware of it.

I've restarted VW and rebooted machine to no avail. Any suggestions? Using VWA 2008 SP3.

TIA, cheers, mmm

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OpenGL is a hardware based render that is implemented in the graphics card - this is why it is quick for interactive rotations. Different graphics cards implement OpenGL in different ways, often using a mix of hardware and software emulation and often as a subset of the full implementation (shadows for example is not available in all OpenGL implementations). So you may well see different results using different hardware and/or video drivers.

I suspect what you are seeing is due to the implementation of OpenGL in the graphics card.

Personally, I would stick with OpenGL for quick and dirty screen previews and use a renderworks mode such as Final Quality Renderworks for presentation views such as in SLVP's where you don't need the interactivity but need a consistent result.

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OpenGL is a hardware based render that is implemented in the graphics card - this is why it is quick for interactive rotations. Different graphics cards implement OpenGL in different ways, often using a mix of hardware and software emulation and often as a subset of the full implementation (shadows for example is not available in all OpenGL implementations). So you may well see different results using different hardware and/or video drivers.

Thanks for the response, that makes sense. I'll try this file on another machine and see what happens.

Personally, I would stick with OpenGL for quick and dirty screen previews and use a renderworks mode such as Final Quality Renderworks for presentation views such as in SLVP's where you don't need the interactivity but need a consistent result.

I agree in concept, unfortunately render times are so long with FQRW that its impacting office workflow. Also, graphically I like the shadows generated in openGL for non-photorealistic orthagonal drwgs. Maybe I should be asking, "what custom RW settings will give me sharp uniform shadows (without "fall off" gradients) and not compromise speed?" Any takers?

Thanks again, mmm

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