On 17.11.2005 12:23, Martin Henne wrote: > Hi all, > > we ran into problems using alpha textures within blender. > The problem is described with some screenshots at > the website below. > > It happens with blend2cs and with blender2crystal: > > http://www.martinhenne.de/alphabug/ > > The blend-files are also available. What could I do to > help improving the converter here? Any more specific > bug reports or something?
What happens there is that the transparent fragments write to the Z buffer as well; hence, you get transparent "occluders". Back to front sorting meshes (caused by specifying the "alpha" priority) can help; however, if objects* overlap, it can still occur that some transparent part occludes geometry. Also, sorting is done based upon the object center, which needs to be taken into account as well. I hope that cleared up the problem a bit :) A converter can't do much here; it's a matter of creating proper artwork. (*) Emphasis on objects; geometry _in_ an object gets not sorted, it's more or less luck whether transparent geometry behind another in an object gets rendered correctly. Ways around include: - Split objects with alpha in such a way that they not overlap. - Don't use a Z mode that writes to the depth buffer; e.g. Ztest instead of Zuse (the results may be slightly wrong, but with e.g. your tree, chances are good noone notices). - Use binary alpha. The result is essentially that fragments with an alpha < 0.5 are not rendered and not written to the Z buffer. However, the other fragments will be renderer fully transparent. Binary alpha makes life easy, but also produces "hard" edges. -f.r.
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