glTexImage2D - single channel blitting

Graphics and GPU Programming Programming

Started by Genjix March 16, 2007 06:05 PM

2 comments, last by Genjix 17 years, 1 month ago

100

Author

March 16, 2007 06:05 PM

Hi, I see the formats GL_RGBA and such, but is there a fast way of doing single channel blitting to a texture rather than storing, and updating a character array which I then have to blit? Thanks.

soconne

105

March 16, 2007 11:51 PM

As long as the channel's data is all contiguous, just use GL_ALPHA for the format. This is assuming your texture data is in GL_ALPHA format. If not, then there is not a way to only update a single channel since the data is not stored contiguously.

Author Freeworld3Dhttp://www.freeworld3d.org

Genjix

100

Author

March 17, 2007 02:50 AM

Thanks so much, that's a great help!

      // to update only R channel from a continuous block of red pixel data      glTexImage2D (textarget, 0, GL_RGBA8, actual_width, 	actual_height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, red_pixels-3);

[Edited by - Genjix on March 17, 2007 4:50:22 AM]

Genjix

100

Author

March 17, 2007 04:17 AM

spoke too soon... this doesn't seem to work (see a black texture) whereas normal GL_RGBA is working there fine. Any ideas why?

[Edited by - Genjix on March 17, 2007 4:17:05 AM]