function constantString=GL_ONE % constantString=GL_ONE % % Return the string 'GL_ONE', which specifies an alpha blending % factor to Screen('BlendFunction', ...). % % "Alpha" is a factor which weights RGB values when combining pixels by % drawing or copying. Alpha values weight the pixels drawn, the "source % surface". Separate alpha values weight the pixels drawn onto, the % "destination surface". A given pixel's alpha factor is not necessarily % the alpha component of that pixel's [rgba] color vector, but may instead % be the other combined surface's alpha component, a function of either or % both both alpha compoenents, a constant, or it may derive from RGB values % of the other combined surface. The Psychtoolbox command % Screen('BlendFunction') selects which. It implements the OpenGL function % "glBlendFunc". % % In MATLAB, Screen('BlendFunction') accepts strings named for C constants % passed to the OpenGL function glBlendFunc().Enter "Help % PsychAlphaBlending" in the MATLAB command window for a list of blending % constants (and other functions related to alpha blending). % % GL_ONE may be used as either a source or a destination factor. % % % see also: PsychAlphaBlending, AlphaDemo, AlphaBlendingTest. constantString='GL_ONE'; return; % HISTORY % % 2/9/05 awi Wrote it % NOTES % % 2/9/05 awi These alpha blending factor functions are an excuse % for documentation, but I don't see anytyhing wrong with that. % By defining them as functions we get them to appear upon "Help % PsychAlphBlendning", which is exaclty the right place to look. % In MATLAB, There is a way to get help on a function. There is no way % to get help on a string. % All constants: % "GL_ZERO", % "GL_ONE", % "GL_SRC_COLOR", % "GL_ONE_MINUS_SRC_COLOR", % "GL_DST_COLOR", % "GL_ONE_MINUS_DST_COLOR", % "GL_SRC_ALPHA", % "GL_ONE_MINUS_SRC_ALPHA", % "GL_DST_ALPHA", % "GL_ONE_MINUS_DST_ALPHA", % "GL_SRC_ALPHA_SATURATE"