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POlibgdx: SpriteBatch, fragment shader on Samsung Android devices work incorrect
 

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  1. POlibgdx: SpriteBatch, fragment shader on Samsung Android devices work incorrect
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    <p>I'm developipng an 2D live wallpaper for Andoid using libgdx and its SpriteBatch class. This is a watch, so all I need, from libgdx is just drawing multiple textures, rotating them to specific angle.</p> <p>I've solved this problem using SpriteBatch class and all was fine. </p> <p>But now I need to add magnifying lens effect to my scene. Task is to magnify specific area with specific ratio to simulate real lens. </p> <p>I've solved this by rendering to FrameBuffer, getting texture region from FrameBuffer and finally, drawing this region with custom shader, using SpriteBatch. </p> <p>THE PROBLEM: on Samsung devices (I've tried on galaxy note N7000, and on Galaxy Tab 10.1) there is a small rectangle in the center of magnifying area about 16x16px, where magnification ratio slightly increases. Sorry, I can't post a screenshot now, because I don't have Samsung device. On other devices all works fine, tried in HTC Vivid, Acer A500, Google Nexus One. </p> <p>I think, the problem if in Mali GPU on Samsung devices, but don't know, how to fix it.</p> <p>I've adapted fragment shader code from this question to SpriteBatch <a href="https://stackoverflow.com/questions/6030814/add-fisheye-effect-to-images-at-runtime-using-opengl-es">Add Fisheye effect to images at runtime using OpenGL ES</a> Here is it:</p> <pre><code>#ifdef GL_ES #define LOWP lowp precision mediump float; #else #define LOWP #endif varying LOWP vec4 v_color; varying vec2 v_texCoords; uniform sampler2D u_texture; void main() { vec2 m = vec2(0.622 , 0.4985); // lens center point, note that in live wallpaper center of texture is (0.5,0.5) float lensSize = 0.045; //diameter of lens float lensCut = 0.0342; //length of cut lines vec2 d = v_texCoords - m; float r = sqrt(dot(d, d)); // distance of pixel from mouse float cuttop = m.y + lensCut; float cutbottom = m.y - lensCut; vec2 uv; if (r &gt;= lensSize) { uv = v_texCoords; } else if ( v_texCoords.y &gt;= cuttop) { uv = v_texCoords; } else if (v_texCoords.y &lt;= cutbottom) { uv = v_texCoords; } else { uv = m + normalize(d) * asin(r) / (3.14159 * 0.37); } gl_FragColor = texture2D(u_texture, uv); } </code></pre> <p>Vertex shader is default from SpriteBatch sources:</p> <pre><code>attribute vec4 a_position; attribute vec4 a_color; attribute vec2 a_texCoord0; uniform mat4 u_projTrans; varying vec4 v_color; varying vec2 v_texCoords; void main() { v_color = a_color; v_texCoords = a_texCoord0; gl_Position = u_projTrans * a_position; } </code></pre> <p>Here is my <code>render()</code> method:</p> <pre><code> GL20 gl = Gdx.graphics.getGL20(); gl.glEnable(GL20.GL_TEXTURE_2D); gl.glActiveTexture(GL20.GL_TEXTURE0); gl.glClearColor(WallpaperService.bg_red, WallpaperService.bg_green, WallpaperService.bg_blue, 1f); gl.glClear(GL20.GL_COLOR_BUFFER_BIT); // Creating framebuffer, if it has gone if (mFrameBuffer == null) { mFrameBuffer = new FrameBuffer(Format.RGBA4444, BG_WIDTH, BG_HEIGHT, true); mFrameBufferRegion = new TextureRegion(mFrameBuffer.getColorBufferTexture()); mFrameBufferRegion.flip(false, true); } //Camera setting according to background texture camera = new OrthographicCamera(BG_WIDTH, BG_HEIGHT); camera.position.set(BG_WIDTH / 2, BG_WIDTH / 2, 0); camera.update(); batch.setProjectionMatrix(camera.combined); //Rendering scene to framebuffer mFrameBuffer.begin(); batch.begin(); //main Drawing goes here batch.end(); //Drawing frame to screen with applying shaders for needed effects if (mFrameBuffer != null) { mFrameBuffer.end(); camera = new OrthographicCamera(width, height); camera.position.set(width / 2, height / 2, 0); camera.update(); batch.setProjectionMatrix(camera.combined); batch.begin(); batch.setShader(null); batch.setShader(shader); batch.draw(mFrameBufferRegion, width / 2 - (BG_WIDTH / 2) + (MARGIN_BG_LEFT * ratio), height / 2 - (BG_HEIGHT / 2) + (MARGIN_BG_TOP * ratio), (float) BG_WIDTH / 2, (float) BG_HEIGHT / 2, (float) BG_WIDTH, (float) BG_HEIGHT, (float) ratio, (float) ratio, 0f); batch.setShader(null); batch.end(); } </code></pre>
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    1. USAlexander Semenov
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