3D surface alpha causing weirdness
Blitz3D Forums/Blitz3D Programming/3D surface alpha causing weirdness
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| I have a 3d model I converted with LWConvert to B3D. It has a alpha in the main surface, but when I use the surface in alpha mode, it's like the zbuffering on the polys gets messed up. It's like the polys are rendering in reverse. They're not flipped though. Any ideas? |
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| Alpha + Polygons == The equivalent of loss of bowel control for polygons. Actually, if the polygons are at the same position then it'll be ordered in order of triangle index. I'd have to see the model to actually attempt to know what's wrong. |
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| i have this exact problem.... one hell of a weird one... |
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| Polys are drawn in creation order, and with alpha are not tested against the z-buffer. Simple as that. You need to sort them so they draw in the correct order. It may or may not help but take a look at my Alfa Zorder in the code archives: http://www.blitzbasic.com/codearcs/codearcs.php?code=850 |
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| why on earth IS that, anyway??? is it a huge bug? |
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| No, it's not a bug. It's just that Blitz3D isn't going to sort them for you. Doesn't take much to sort the polygons based on distance from the camera, just get the distance of'em all (or all those that are facing the camera) inside an array then run a quicksort on it. It's what I do for a great deal of my stuff that uses alpha blending (vertex alpha, typically, but it's generally the same result to me). |
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| yeah its not a bug exactly, just something that blitz doesn't support too well. Just about every engine I have used had similar issues just not as prolific, and often you could set a sort order in the z buffer for a mesh which was a bit better than no real z sorting at all, which seems to be what blitz has. dob't really understand this stuff much myself though :) |
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| There is a faq entry you may find useful: [faq 32] |
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