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performance option, I added a flag to control whether the depth writing pass is performed. Since text is alpha-blended when rendering, it is placed in the transparent bin and rendered back to front. Writing to the depth buffer should therefore be unnecessary. Indeed, rendering something behind text (or any blended object) after that object is drawn will give incorrect results whether the depth buffer is written or not. I therefore think it is safe to keep this option off by default. Users can turn it on for any special needs they have. I did not fix the existing backdrop implementations to work with the new code since this new method of rendering intrinsically handles backdrops correctly. Its results are more accurate than all of the existing backdrop implementations. Its only downside is that it requires two passes if depth buffer updates are desired, whereas DEPTH_RANGE and POLYGON_OFFSET achieve their (less accurate) results in one pass. The NO_DEPTH_BUFFER method also only uses one pass, but it disables depth tests and not depth writes so will have serious problems if anything is drawn in front of the text before OR after the text is drawn. Given the better all-around behavior of the new method, I believe the other backdrop implementations can be safely removed. Code that adjusts the backdrop implementation will of course be broken if the member functions are removed. For this reason I left them in, but set the new rendering method as the default backdrop implementation. At the very least I think the old backdrop implementations should be deprecated and removed at a later date. " Note from Robert Osfield, testing this submission with osgtext I found that the text would not render correctly when different text labels were overlapping in deth and screen space. I change _enableDepthWrites to default to true and found the that which artifacts still occurred around the alpha blended edges the artifacts where better than issue with occlusion of nearer pixels that was happening with _enableDepthWrites set to false.I therefore set the _enableDepthWrites to true as I feel it's the lesser of the two artefacts. |
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