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POiPhone iOS5 querying OpenGL ES 2.0 pipeline objects if they are hidden in the view or not..."Occlusion"
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copied!<p>EXT_occlusion_query_boolean is new with OS5.0,</p> <p>it looks to me like not a single person on the entire internet has posted about these new extensions nor used this code.... </p> <p>so here they are set up properly...which is not documented anywhere as far as i can tell... you can imagine how they would go in your code from this little sudo code here: </p> <pre><code>import UIKit/UIKit.h import GLKit/GLKit.h import "GLProgram.h" GLuint testBox,hasBeenTested,theParams; //... glGenQueriesEXT(1, &testBox); glBeginQueryEXT(GL_ANY_SAMPLES_PASSED_EXT, testBox); //... draw an object ....... glEndQueryEXT(GL_ANY_SAMPLES_PASSED_EXT); glGetQueryObjectuivEXT(testBox, GL_QUERY_RESULT_AVAILABLE_EXT, &hasBeenTested); if (hasBeenTested) glGetQueryObjectuivEXT(testBox, GL_QUERY_RESULT_EXT, &theParams); glDeleteQueriesEXT(1, &testBox); if (!theParams) object is hidden; don't draw next time; </code></pre> <p>hopefully some here can use this code, i've tested it and it works, however, there appears to be a bug in GLKit, where if you use self.effect2 = [[GLKBaseEffect alloc] init]; type of GLKit code to render an object, rather than a normal GLES2.0 pipeline, the queries will fail to give you the correct answer... (never hidden) although i tested a pipeline object hiding a GLKBaseEffect object, (which fails) so it could be there is a bug just mixing the two types, if you go the other way, have a GLKBaseEffect object hide a pipeline object, it gives the correct answer, i did not test further yet.</p> <p>so the question is, I bet i can go further with this and create collision detection in the vertex/fragment shader somehow... this code i found looks like a start... given these two pieces of sudo code, can someone get me closer to collision detection that just triggers when a "part" goes completely inside another part? a quicker easier/firststep could be to have the entire object hidden inside another object before a positive is triggered, this would be a great start, any ideas?</p> <p><a href="http://ucv.academia.edu/Rhadam%C3%A9sCarmona/Papers/743483/Volume-Surface_Collision_Detection" rel="noreferrer">http://ucv.academia.edu/RhadamésCarmona/Papers/743483/Volume-Surface_Collision_Detection</a></p> <p><img src="https://i.stack.imgur.com/s5LjD.png" alt="http://ucv.academia.edu/RhadamésCarmona/Papers/743483/Volume-Surface_Collision_Detection"></p>

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