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POiOs OpenGL ES 2.0 adding textures with low opacity on device and on simulator
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copied!<p>I have a problem with multiple drawing of textures in my program.</p> <p>Blending mode is</p> <pre><code>glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA); glBlendEquation(GL_FUNC_ADD); </code></pre> <p>The value of a-channel is passed into the shader from cpu-code.</p> <pre><code>precision highp float; uniform sampler2D tShape; uniform vec4 vColor; uniform float sOpacity; varying vec4 texCoords;\n" void main() { float a = texture2D(tShape, texCoords.xy).x * sOpacity; gl_FragColor = vec4(vColor.rgb, a); } </code></pre> <p>It's calculated previously with</p> <pre><code>O = pow(O, 1.3); </code></pre> <p>for the best visual effect.</p> <p>I draw with color (0; 0; 0) on the black transparent canvas (0;0;0;0), but with very low opacity:</p> <pre><code>0.03 -> 0.01048 0.06 -> 0.0258 0.09 -> 0.0437 0.12 -> 0.0635 ... </code></pre> <p>I expect, that maximal value of point's color will be (0;0;0;1) (black, no transparent) after multiple drawings as on the simulator: <img src="https://i.stack.imgur.com/kl8tZ.png" alt="enter image description here"></p> <p>but it isn't so on the device: <img src="https://i.stack.imgur.com/cijMd.png" alt="enter image description here"></p> <p>Do you have any ideas, why is it so?</p> <p><strong>UPDATE:</strong></p> <p>Also manual blending works incorrect too (and with difference from standard).</p> <pre><code>glBlendFunc(GL_ONE, GL_ZERO); </code></pre> <p>Fragment shader code:</p> <pre><code>#extension GL_EXT_shader_framebuffer_fetch : require precision highp float; uniform sampler2D tShape; uniform vec4 vColor; uniform float sOpacity; varying vec4 texCoords; void main() { float a = texture2D(tShape, texCoords.xy).x * sOpacity; gl_FragColor = vec4(vColor.rgb * a, a) + (gl_LastFragData[0] * (1.0 - a)); } </code></pre> <p>Result on the simulator: <img src="https://i.stack.imgur.com/vB6g8.png" alt="enter image description here"></p> <p>Result on the device: <img src="https://i.stack.imgur.com/ypNxD.png" alt="enter image description here"></p>

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