Hi there, my two cents: Maybe its a wrong blend function involved? GL_ONE_MINUS_SRC_ALPHA?
http://www.opengl.org/sdk/docs/man/xhtml/glBlendFunc.xml best, Achim Breidenbach Boinx Software Ltd. On 03.03.2013, at 20:23, George Toledo wrote: > Check your alpha values to make sure they're doing what you think they will. > Remember that if your alpha channel has a 0 value in any of the patches that > create your effect that they may not render how you think they will if your > app window actually allows alpha to be "clear". > > For example, a "clear" patch which has a default value of vec4(0,0,0,0) will > create a "clear"/see through effect when rendering to a window that allows > alpha transparency. > > On Mar 2, 2013, at 5:14 PM, Gordon Apple <g...@ed4u.com> wrote: > >> I’m trying to implement a spotlight-type effect in a QCComposition presented >> in a QCCompositionLayer. I want this to be implemented as a composition, >> without mucking with the layer. I do change the layer’s scale and position >> as needed. This is in a family of effects in which the user picks what .qtz >> file to use. The QCCompositionLayer overlays the main presentation layers. >> I want the QCCompositionLayer to dim everything behind it, leaving a clear >> undimmed circle. >> >> I have been able to get this effect in the QC rendering view, using a >> full-screen image billboard behind my effects billboard. However, when I >> use it (without the full-screen image billboard ) in in the >> QCCompositionLayer in my main program, the effect comes out reversed, i.e., >> the circle is dimmed and the background is undimmed — obviously, not what I >> want. Any suggestions as to how I can get the desired effect, preferably >> without changing the QCCompositionLayer itself? >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> Quartzcomposer-dev mailing list (Quartzcomposer-dev@lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> https://lists.apple.com/mailman/options/quartzcomposer-dev/gtoledo3%40gmail.com >> >> This email sent to gtole...@gmail.com > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Quartzcomposer-dev mailing list (Quartzcomposer-dev@lists.apple.com) > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/quartzcomposer-dev/achim%40boinx.com > > This email sent to ac...@boinx.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Quartzcomposer-dev mailing list (Quartzcomposer-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/quartzcomposer-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
