Imagination PowerVR SDK Blog

glCompressedTexSubImage2D()


#1


Hi,

 

I support developping Embedded Graphics System.

I use OpenGL ES 1.1 on Freescale i.MX31 (ARM11+MBX 533MHz).

 

I want to know if MBX's OpenGLES 1.1 supports " glCompressedTexSubImage2D()".

If it is true, I want the detail about this function.<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />


Because I cannot find any information on public document as follows.


http://www.khronos.org/opengles/documentation/opengles1_0/html/glCompressedTexSubImage2D.html



 



>


 format


 Specifies the format of the pixel data. Currently, there is no supported format.


 


Can anyone help me?


#2

Hello,


No, MBX does not supports glCompressedTexSubImage2D(). Texture compression is a very expensive operation that cannot be done on the fly. Besides, It is not possible just to upload part of a PVRTC texture as all adjacent blocks contribute to the colour.


Regards.


Carlos.


#3

Hi Carlos,<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />


 


I am sorry my late response.


Thanks for your information. This is very important.


 


I've never heard that MBX is NOT support glCompressedTexSubImage2D() from the vendor in <?: prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Japan.


 


 


 Akihiro Iseno


 TOMEN Electronics Corp. <http://www.tomen-ele.co.jp>


     Engineering Dept.


     Amusement SBU, Sales Division II


#4

Hi Carlos,<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />


 


You said that "Texture compression is a very expensive operation that cannot be done on the fly."


 


Does MBX support glCompressedTexImage2D() operation?


Which operation is speedy, glCompressedTexImage2D() or glTexImage2D() on MBX?


 


   Akihiro Iseno


#5

Dear Iseno-san,
Texture compression is done offline by our PVRTC Utility. The API uses glCompressedTexImage2D just to upload the pre-compressed data in memory, so it is as fast as glTexImage2D.
The user cannot not modify this data on any way because it is expensive to re-compress so glCompressedTexSubImage2D is not supported. If this kind of functionality is required please use a 16-bit texture format.


Best regards.


Carlos.


#6

Dear Carlos-san,<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />


 


Thanks for good information.


I will try to do it. :-)


 


Yours sincerely,


 


Akihiro Iseno


 TOMEN Electronics Corp. <http://www.tomen-ele.co.jp>


     Engineering Dept.


     Amusement SBU, Sales Division II