This should be enough to make your fading work correctly.
Thus gl_FragColor = texture2D(u_baseMap, v_texCoords) īecomes simply gl_FragColor = texture2D(u_baseMap, v_texCoords) * opacity Since you are multiplying your texture alpha with another value, you have to do the same for texture color channels as well. What you were missing was taking premultiplied alpha into account in the shader. Instead of SRC_ALPHA,1-SRC_ALPHA you need to use 1,1-SRC_ALPHA as you have already tried. Normal alpha blending then requires different blend function. Premultiplied alpha just means that all input color values are already multiplied with the alpha value. It solves among some other issues bleeding of neighbour texels when using bilinear filtering for translucent images. make your content pipeline harder, you should. If you can use premultiplied alpha and it doesn't e.g.
It's also possible to do that without any additional memory penalty at least by doing it completely on the native side, but I don't go to the details here. There are ways to load images without premultiplication in Android as suggested in this thread. Thank you for the suggestions, as highlighted in the accepted answer in the end I didn't need to load without with "straight alpha" as I was able to correctly work with the pre-multiplied version that Android loads by default by changing the 2nd line of my Fragment shader to: "gl_FragColor *= "+opVal+" "+ Then it will display perfectly at full opacity (1.0f) but becomes 'oversaturated' (This is the best way I can describe it) the more transparency you introduce (ie 0.9f down to 0.0f). Enable Alpha blending and set blending function GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA) Using this, the semi-transparent parts of the image will display too dark (including a dark border where anti-aliased edges should be) but will fade in and out (It's just no good though as the image isn't correct). GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4) GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA) Enable Alpha blending and set blending function "gl_FragColor.a *= "+opVal+" "+ //where opVal is a value from 0.0f to 1.0fĪnd then. "gl_FragColor = texture2D(u_baseMap, v_texCoords) " + the resulting 2D images into a single, final image called the composite. My game has 1 or 2 images which have semi-transparent pixels and I need to be able to fade them in and out but this doesn't seem possible easily.Īs far as I understand Android always loads graphics in premultiplied alpha format, but if this is the case, how to blend them correctly?ĮDIT I have included some code: String strFShader = In computer graphics, alpha compositing or alpha blending is the process of combining one. The BLENDFUNCTION structure controls blending by specifying the blending functions for source and destination bitmaps.Is this possible? To load textures in non-premultiplied format (Straight alpha?)?
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