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POGLKit: Drawing Points using GL_POINTS
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copied!<p>I am picking up the opengl es 2.0 with GLKit. I can successfully draw shapes like squares, triangles, cube etc.</p> <p>I have problem drawing points, here is my code which isn't working on device (iPod 4), though I can see the Points/dots in retina simulator.</p> <pre><code>- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect { //White background color glClearColor(1.0, 1.0, 1.0, 1.0); glClear(GL_COLOR_BUFFER_BIT); [self.effect prepareToDraw]; //USING _program glUseProgram(_program); GLfloat vert[] = {0,0, 0.1,0.1, 0.2,0.2, 0.3,0.3, 0.4,0.4, 0.5,0.5}; glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer); glEnableVertexAttribArray(GLKVertexAttribPosition); glVertexAttribPointer(GLKVertexAttribPosition, 2, GL_FLOAT, GL_FALSE, 0, vert); glDrawArrays(GL_POINTS, 0, 5); glDisableVertexAttribArray(GLKVertexAttribPosition); } </code></pre> <p>and here is my update method just for ref:</p> <pre><code>- (void)update { float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height); GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 4.0f, 10.0f); self.effect.transform.projectionMatrix = projectionMatrix; //Since visible range is 4 to 10 so have to mave back in z GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -6.0f); self.effect.transform.modelviewMatrix = modelViewMatrix; } </code></pre> <p>and following is how I am defining the effect:</p> <pre><code>self.effect = [[GLKBaseEffect alloc] init]; self.effect.useConstantColor = GL_TRUE; self.effect.constantColor = GLKVector4Make(0.0, 0.0, 1.0, 1.0); //Blue color </code></pre> <p>So that the points are visible on white background.</p> <p>Can someone point any flaw in this code? I am not sure why it isn't showing on device since triangles, squares and cubes where all visible. Any help is appreciated.</p> <p><strong>Edit:</strong></p> <p>I have not used shaders before so this is my first time. As Ben mentioned the example code. Here's now what I am doing:</p> <p>I have <strong>VertexShader.glsl</strong> and <strong>FragmentShader.glsl</strong> files:</p> <p><strong>VertexShader.glsl</strong></p> <pre><code>void main() { gl_PointSize = 10.0; } </code></pre> <p><strong>FragmentShader.glsl</strong></p> <pre><code>void main() { } </code></pre> <p>I am setting up the shader just before I create the effect and just after I set EAGLContext:</p> <pre><code>// Setup shader GLuint vertexShader = [self createShaderWithFile:@"VertexShader.glsl" type:GL_VERTEX_SHADER]; GLuint fragmentShader = [self createShaderWithFile:@"FragmentShader.glsl" type:GL_FRAGMENT_SHADER]; _program = glCreateProgram(); glAttachShader(_program, vertexShader); glAttachShader(_program, fragmentShader); glLinkProgram(_program); GLint linked = 0; glGetProgramiv(_program, GL_LINK_STATUS, &linked); if (linked == 0) { glDeleteProgram(_program); return; } </code></pre> <p>And here is the createShaderWithFile method:</p> <pre><code>- (GLuint)createShaderWithFile:(NSString *)filename type:(GLenum)type { GLuint shader = glCreateShader(type); if (shader == 0) { return 0; } NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:filename]; NSString *shaderString = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil]; const GLchar *shaderSource = [shaderString cStringUsingEncoding:NSUTF8StringEncoding]; glShaderSource(shader, 1, &shaderSource, NULL); glCompileShader(shader); GLint success = 0; glGetShaderiv(shader, GL_COMPILE_STATUS, &success); if (success == 0) { char errorMsg[2048]; glGetShaderInfoLog(shader, sizeof(errorMsg), NULL, errorMsg); NSString *errorString = [NSString stringWithCString:errorMsg encoding:NSUTF8StringEncoding]; NSLog(@"Failed to compile %@: %@", filename, errorString); glDeleteShader(shader); return 0; } return shader; } </code></pre> <p>I have also updated the drawRect method above.</p> <p>Here is the link to this project: <a href="http://dl.dropbox.com/u/36638938/Template.zip" rel="nofollow">http://dl.dropbox.com/u/36638938/Template.zip</a></p>

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