[Interest] Quick3D mapping of png textures onto Item 3D

[Till Oliver Knoll]

2012/9/18 Satya Praveen Ganapathi <praveen.s at hmie.co.in>:
> ...
> However, the png image is not getting displayed properly in 3D space i.e.
> transparent area of the png file is
> shown as black shaded.

Most probably you simply need to enable "alpha blending": In OpenGL
terms that usually means

a) Turn blending on: glEnable(GL_BLEND)
b) Define a blend function, e.g.: glBlendFunc(GL_SRC_ALPHA,
GL_ONE_MINUS_SRC_ALPHA)

Note: "Premultiplied alpha" textures (refer to Wikipedia or the Qt
docs about the same topic) are to be preferred, in which case you
would say glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

Here is a guy who is trying /exactly/ the same thing as you:

  http://galfar.vevb.net/imaging/smf/index.php?topic=296.0

Depending on what you are trying to achieve the function glTexEnv()
with argument GL_BLEND might be useful too (if you want to apply alpha
blending at the moment when applying the texture - and if you want
that the underlying surface colour shines through). Refer to the
(possibly outdated) FAQ:

  http://www.opengl.org/archives/resources/faq/technical/transparency.htm


How you apply all this to Qt 3D I don't know - but I'm sure there must
be this big "Enable blending" switch somewhere, too - refer to the
docs (and if not, to my little understanding you can still mix in your
own "raw OpenGL" code as above, no?).

Cheers, Oliver