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Guoshima

Early-z, Depth pass and Double Speed Rendering

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Hello, I have a few questions regarding the usage of Early-Z and Double Speed Rendering. At the beginning of the frame, we render all the visible objects to a depth texture, storing the linear depth to the camera. This texture is then later used for other effects such as shadows, volumetric fog, water, ... But during the rendering of this pass I would like to make use of double speed depth-only rendering and later during the shading of the scene use the depth-pass data for early-z culling. But I have some problems doing so. To be able to use double speed rendering, I'm not allowed to render to the color buffer, and may not use alpha testing or texkill. This introduces problems (depth-tested grass and trees for example). It would still be possible, and simply don't render any objects which have alpha properties. Also, I have to create a depth-rendertarget for this, but I presume I can't use the depth-data in that offscreen buffer as depth/stencil buffer during the rendering of my main back/front-buffer. Because I would like to use the depth-data in that ofscreen-target for early-z. I presume someone must have had these issues before. Any suggestions on this? Regards, Kenzo

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Usually in the depth only pass you are totally vertex fetch/shader bound so it doesn't matter whether you get double fill rate or not. (unified GPU's being the exception) I suggest seeing if this is the case for you so that you don't waste time trying to optimize something that isn't your bottleneck.

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