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Texture alpha usage

Original Post by: Mon Jun 15 10:35:51 2015


How can we get the usage (mask/transparency) of the alpha value in texture files of CDB ?


Original Post by: Salah Mon Jun 15 15:53:52 2015


Hi,


As I understand it, you want to know if 3D Models in CDB can have textures with transparency (Alpha channel). Am I correct?


Best regards,

Salah

Original Post by: Tue Jun 16 06:28:09 2015


Hi,


As I understand it, you want to know if 3D Models in CDB can have textures with transparency (Alpha channel). Am I correct?


Best regards,

Salah


I know they have transparency, i just do not know whether to use alpha channel for transparency (for example; for glass) or to use the alpha channel for masking (for example; the leaves of a tree). In other words, i don't know how to interpret alpha channel.


Thanks.

Original Post by: Salah Tue Jun 16 20:20:37 2015


Hi,


Chapter 6 specifies what the alpha channel of a texture represents depending on its intended use.


See section 6.13.5 for details. For instance, in a Night Map, the alpha channel is a mask.


Regards,

Salah

Original Post by: Wed Jun 17 10:40:43 2015


Thank you. It helps much.


Kind regards.

Original Post by: RyanFranz Wed Jun 17 14:33:06 2015


I'm not sure that was a full answer to the question...


Some rendering devices do need to know the difference between two different uses for an alpha channel (transparency or masking), where either one could be used in a base texture. The CDB spec doesn't differentiate between the two uses, and must leave it up to clients to determine which use of the alpha channel is intended (if needed).

Original Post by: B. Leclerc Fri Jun 19 22:11:04 2015


BTW, this question should have been directed to the CDB Specification Forum as opposed to the CDB API Forum.

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