![](\"https:\/\/writingagame.com\/img\/b01\/c22\/01.jpg\")
<\/p>\n\n\n\nWhen screen size changed, we need to re-position the camera to fit new screen size optimally. For example, in our case optimal scene\/”stage” size would be, let’s say, 500×300 (to fit our spinning box into the screen). Our camera’s view angle is 30 degrees.<\/p>\n\n\n\n
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so, ?<\/strong> \/ 250 = cosine(15) \/ sine(15) = cotangent(15)<\/em><\/p>\n\n\n\n ?<\/strong> = 250 * cotangent(15) = 250 * 3.73 = 923<\/em><\/p>\n\n\n\n which is almost the same as our hard-coded 1000 (line 69 in TheGame.cpp<\/em>) and doesn’t explain why we don’t fit screen on Android.<\/p>\n\n\n\n First, we don’t count screen resolution, and second:<\/p>\n\n\n\n Start VS, open C:\\CPP\\a997modeler<\/em>\\p_windows\\p_windows.sln<\/em>, run the project, play with window size (from tall and narrow to short and wide). You will note (it was a surprise to me) that our 1000 camera distance defines only VERTICAL fit, not horizontal one. But we don’t need to fit 500 size units vertically, vertically we need just 300, so<\/p>\n\n\n\n cameraDistanceV (vertical) = 150 * cotangent(15)<\/em><\/p>\n\n\n\n For horizontal fit we need to count also screen aspect ratio, which is screen width \/ height, so<\/p>\n\n\n\n cameraDistanceH (horizontal) = 250 * cotangent(15) \/ screenAspectRatio<\/em><\/p>\n\n\n\n For example, my S20 phone screen size is 1080 X 2400, so<\/p>\n\n\n\n screenAspectRatio = 1080 \/ 2400 = 0.45<\/em><\/p>\n\n\n\n cotangent(15) = 3.73<\/em>, so:<\/p>\n\n\n\n cameraDistanceV = 150 * cotangent(15) = 150 * 3.73 = 560<\/em><\/p>\n\n\n\n cameraDistanceH = 250 * cotangent(15) \/ screenAspectRatio = 250 * 3.73 \/ 0.45 = 2072<\/em><\/p>\n\n\n\n For our camera we’ll pick the greater value, 2072<\/strong>, which looks quite reasonable. From SUCH distance it surely will fit.<\/p>\n\n\n\n Now, if we flip the phone horizontally, screen size will switch to 2400 X 1080. so<\/p>\n\n\n\n screenAspectRatio = 2400 \/ 1080 = 2.22<\/em>, so:<\/p>\n\n\n\n cameraDistanceV<\/strong> <\/em>remains the same, 560<\/em>, when horizontal one<\/p>\n\n\n\n cameraDistanceH = 250 * cotangent(15) \/ screenAspectRatio = 250 * 3.73 \/ 2.22 = 420<\/em>, so this time we’ll pick the greater vertical value, 560<\/strong>, which is logical, now fitment will be defined by screen vertical <\/strong>size limit.<\/p>\n\n\n\n NOW we have adaptive camera positioning.<\/p>\n\n\n\n Implementation<\/strong>:<\/p>\n\n\n\n Open TheGame.h<\/em> and replace the code by:<\/p>\n\n\n <\/p>\n\n\n\n In TheGame::getReady(), TheGame::drawFrame()<\/em> and in TheGame::onScreenResize()<\/em> we have camera related changes. Also we’ll move camera-related calculations from TheGame <\/em>to the Camera <\/em>class.<\/p>\n\n\n\n 2. Open TheGame.cpp<\/em> and replace the code by:<\/p>\n\n\n <\/p>\n\n\n\n 3. In Camera <\/em>class we have new variables and functionality.<\/p>\n\n\n\n Open Camera.h<\/em> and replace the code by:<\/p>\n\n\n <\/p>\n\n\n\n 4. Under xEngine <\/em>add new C++ file, name: Camera.cpp<\/strong><\/p>\n\n\n\n Location: C:\\CPP\\engine\\<\/em><\/p>\n\n\n\n Code:<\/p>\n\n\n <\/p>\n\n\n\n 5. Build and run.<\/p>\n\n\n\n Looks good.<\/p>\n\n\n\n 6. Close and re-start VS. Open C:\\CPP\\a997modeler\\p_android\\p_android.sln<\/em>. <\/p>\n\n\n\n 7. Under xEngine <\/em>add existing item Camera.cpp<\/em> from C:\\CPP\\engine<\/em><\/p>\n\n\n\n Add screen resize handling to myglPollEvents()<\/em>.<\/p>\n\n\n\n 8. Open myplatform.cpp<\/em> and replace code by:<\/p>\n\n\n <\/p>\n\n\n\n 9. Switch on, unlock, plug in, allow.<\/p>\n\n\n\n Build and run:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" When screen size changed, we need to re-position the camera to fit new screen size optimally. For example, in our case optimal scene\/”stage” size would be, let’s say, 500×300 (to fit our spinning box into the screen). Our camera’s view angle is 30 degrees. so, ? \/ 250 = cosine(15) \/ sine(15) = cotangent(15) ? […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-697","post","type-post","status-publish","format-standard","hentry","category-cross-platform-3d"],"_links":{"self":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/697","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/comments?post=697"}],"version-history":[{"count":11,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/697\/revisions"}],"predecessor-version":[{"id":719,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/697\/revisions\/719"}],"wp:attachment":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/media?parent=697"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/categories?post=697"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/tags?post=697"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n\n\n\n\n#pragma once\n#include <vector>\n#include "GameSubj.h"\n#include "Camera.h"\n\nclass TheGame\n{\npublic:\n\tint screenSize[2];\n\tfloat screenAspectRatio = 1;\n\tbool bExitGame;\n\tCamera mainCamera;\n\tfloat dirToMainLight[4] = { 1,1,1,0 };\n\n\t\/\/static arrays (vectors) of active GameSubjs\n\tstatic std::vector<GameSubj*> gameSubjs;\npublic:\n\tint run();\n\tint getReady();\n\tint drawFrame();\n\tint cleanUp();\n\tint onScreenResize(int width, int height);\n};\n\n<\/pre><\/div>\n\n\n
\n\n\n\n\n#include "TheGame.h"\n#include "platform.h"\n#include "utils.h"\n#include "linmath.h"\n#include "Texture.h"\n#include "Shader.h"\n#include "DrawJob.h"\n#include "ModelBuilder.h"\n#include "TexCoords.h"\n\nextern std::string filesRoot;\nextern float degrees2radians;\n\nstd::vector<GameSubj*> TheGame::gameSubjs;\n\nint TheGame::getReady() {\n bExitGame = false;\n Shader::loadShaders();\n glEnable(GL_CULL_FACE);\n\n \/\/=== create box ========================\n GameSubj* pGS = new GameSubj();\n gameSubjs.push_back(pGS);\n\n pGS->name.assign("box1");\n pGS->ownCoords.setPosition(0, 0, 0);\n pGS->ownCoords.setDegrees(0, 0, 0);\n pGS->ownSpeed.setDegrees(0,1,0);\n\n ModelBuilder* pMB = new ModelBuilder();\n pMB->useSubjN(gameSubjs.size() - 1);\n\n \/\/define VirtualShape\n VirtualShape vs;\n vs.setShapeType("box-tank");\n vs.whl[0] = 60;\n vs.whl[1] = 160;\n vs.whl[2] = 390;\n vs.setExt(20);\n vs.extD = 0;\n vs.extF = 0; \/\/to make front face "flat"\n vs.sectionsR = 2;\n\n Material mt;\n \/\/define material - flat red\n mt.shaderN = Shader::spN_phong_ucolor;\n mt.primitiveType = GL_TRIANGLES;\n mt.uColor.setRGBA(255, 0, 0,255); \/\/red\n pMB->useMaterial(&mt);\n\n pMB->buildBoxFace(pMB,"front v", &vs);\n pMB->buildBoxFace(pMB, "back v", &vs);\n pMB->buildBoxFace(pMB, "top", &vs);\n pMB->buildBoxFace(pMB, "bottom", &vs);\n pMB->buildBoxFace(pMB, "left all", &vs);\n\n mt.uColor.clear(); \/\/ set to zero;\n mt.uTex0 = Texture::loadTexture(filesRoot + "\/dt\/sample_img.png");\n mt.shaderN = Shader::spN_flat_tex;\n pMB->useMaterial(&mt);\n TexCoords tc;\n tc.set(mt.uTex0, 11, 12, 256, 128, "180");\n pMB->buildBoxFace(pMB, "right all", &vs, &tc);\n\n pMB->buildDrawJobs(gameSubjs);\n\n delete pMB;\n\n \/\/===== set up camera\n mainCamera.ownCoords.setDegrees(15, 180, 0); \/\/set camera angles\/orientation\n mainCamera.viewRangeDg = 30;\n mainCamera.stageSize[0] = 500;\n mainCamera.stageSize[1] = 375;\n memcpy(mainCamera.lookAtPoint, pGS->ownCoords.pos, sizeof(float) * 3);\n mainCamera.onScreenResize();\n\n \/\/===== set up light\n v3set(dirToMainLight, -1, 1, 1);\n vec3_norm(dirToMainLight, dirToMainLight);\n\n return 1;\n}\nint TheGame::drawFrame() {\n myPollEvents();\n\n \/\/glClearColor(0.0, 0.0, 0.5, 1.0);\n glClear(GL_COLOR_BUFFER_BIT);\n\n \/\/calculate halfVector\n float dirToCamera[4] = { 0,0,-1,0 }; \/\/-z\n mat4x4_mul_vec4plus(dirToCamera, *mainCamera.ownCoords.getRotationMatrix(), dirToCamera, 0);\n\n float uHalfVector[4] = { 0,0,0,0 };\n for (int i = 0; i < 3; i++)\n uHalfVector[i] = (dirToCamera[i] + dirToMainLight[i]) \/ 2;\n vec3_norm(uHalfVector, uHalfVector);\n\n mat4x4 mProjection, mViewProjection, mMVP, mMV4x4;\n \/\/mat4x4_ortho(mProjection, -(float)screenSize[0] \/ 2, (float)screenSize[0] \/ 2, -(float)screenSize[1] \/ 2, (float)screenSize[1] \/ 2, 100.f, 500.f);\n float nearClip = mainCamera.focusDistance - 250;\n float farClip = mainCamera.focusDistance + 250;\n mat4x4_perspective(mProjection, mainCamera.viewRangeDg * degrees2radians, screenAspectRatio, nearClip, farClip);\n mat4x4_mul(mViewProjection, mProjection, mainCamera.lookAtMatrix);\n \/\/mViewProjection[1][3] = 0; \/\/keystone effect\n\n \/\/scan subjects\n int subjsN = gameSubjs.size();\n for (int subjN = 0; subjN < subjsN; subjN++) {\n GameSubj* pGS = gameSubjs.at(subjN);\n \/\/behavior - apply rotation speed\n pGS->moveSubj();\n \/\/prepare subject for rendering\n pGS->buildModelMatrix(pGS);\n \/\/build MVP matrix for given subject\n mat4x4_mul(mMVP, mViewProjection, pGS->ownModelMatrix);\n \/\/build Model-View (rotation) matrix for normals\n mat4x4_mul(mMV4x4, mainCamera.lookAtMatrix, (vec4*)pGS->ownCoords.getRotationMatrix());\n \/\/convert to 3x3 matrix\n float mMV3x3[3][3];\n for (int y = 0; y < 3; y++)\n for (int x = 0; x < 3; x++)\n mMV3x3[y][x] = mMV4x4[y][x];\n \/\/render subject\n for (int i = 0; i < pGS->djTotalN; i++) {\n DrawJob* pDJ = DrawJob::drawJobs.at(pGS->djStartN + i);\n pDJ->execute((float*)mMVP, *mMV3x3, dirToMainLight, uHalfVector, NULL);\n }\n }\n mySwapBuffers();\n return 1;\n}\n\nint TheGame::cleanUp() {\n int itemsN = gameSubjs.size();\n \/\/delete all UISubjs\n for (int i = 0; i < itemsN; i++) {\n GameSubj* pGS = gameSubjs.at(i);\n delete pGS;\n }\n gameSubjs.clear();\n \/\/clear all other classes\n Texture::cleanUp();\n Shader::cleanUp();\n DrawJob::cleanUp();\n return 1;\n}\nint TheGame::onScreenResize(int width, int height) {\n if (screenSize[0] == width && screenSize[1] == height)\n return 0;\n screenSize[0] = width;\n screenSize[1] = height;\n screenAspectRatio = (float)width \/ height;\n glViewport(0, 0, width, height);\n mainCamera.onScreenResize();\n mylog(" screen size %d x %d\\n", width, height);\n return 1;\n}\nint TheGame::run() {\n getReady();\n while (!bExitGame) {\n drawFrame();\n }\n cleanUp();\n return 1;\n}\n\n<\/pre><\/div>\n\n\n
\n\n\n\n\n#pragma once\n#include "Coords.h"\n#include "linmath.h"\n\nclass Camera\n{\npublic:\n\tCoords ownCoords;\n\tmat4x4 lookAtMatrix;\n\tfloat lookAtPoint[3] = { 0,0,0 };\n\tfloat focusDistance = 100;\n\tfloat viewRangeDg = 30;\n\tfloat stageSize[2] = { 500, 375 };\npublic:\n\tfloat pickDistance() { return pickDistance(this); };\n\tstatic float pickDistance(Camera* pCam);\n\tvoid setCameraPosition() { setCameraPosition(this); };\n\tstatic void setCameraPosition(Camera* pCam);\n\tvoid buildLookAtMatrix() { buildLookAtMatrix(this); };\n\tstatic void buildLookAtMatrix(Camera* pCam);\n\tvoid onScreenResize() { onScreenResize(this); };\n\tstatic void onScreenResize(Camera* pCam);\n};\n\n<\/pre><\/div>\n\n\n
\n\n\n\n\n#include "Camera.h"\n#include "TheGame.h"\n#include "utils.h"\n\nextern TheGame theGame;\nextern float degrees2radians;\n\nfloat Camera::pickDistance(Camera* pCam) {\n\tfloat cotangentA = 1.0f \/ tanf(degrees2radians * pCam->viewRangeDg \/ 2);\n\tfloat cameraDistanceV = pCam->stageSize[1] \/ 2 * cotangentA;\n\tfloat cameraDistanceH = pCam->stageSize[0] \/ 2 * cotangentA \/ theGame.screenAspectRatio;\n\tpCam->focusDistance = fmax(cameraDistanceV, cameraDistanceH);\n\treturn pCam->focusDistance;\n}\nvoid Camera::setCameraPosition(Camera* pCam) {\n\tv3set(pCam->ownCoords.pos, 0, 0, -pCam->focusDistance);\n\tmat4x4_mul_vec4plus(pCam->ownCoords.pos, *pCam->ownCoords.getRotationMatrix(), pCam->ownCoords.pos, 1);\n\tfor (int i = 0; i < 3; i++)\n\t\tpCam->ownCoords.pos[i] += pCam->lookAtPoint[i];\n}\nvoid Camera::buildLookAtMatrix(Camera* pCam) {\n\tfloat cameraUp[4] = { 0,1,0,0 }; \/\/y - up\n\tmat4x4_mul_vec4plus(cameraUp, *pCam->ownCoords.getRotationMatrix(), cameraUp, 0);\n\tmat4x4_look_at(pCam->lookAtMatrix, pCam->ownCoords.pos, pCam->lookAtPoint, cameraUp);\n}\nvoid Camera::onScreenResize(Camera* pCam) {\n\tpCam->pickDistance();\n\tpCam->setCameraPosition();\n\tpCam->buildLookAtMatrix();\n}\n\n<\/pre><\/div>\n\n\n
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\n\n\n\nAndroid<\/h2>\n\n\n\n
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\n\n\n\n\n#include <android\/log.h>\n#include "stdio.h"\n#include "TheGame.h"\n#include <sys\/stat.h>\t\/\/mkdir for Android\n\nextern struct android_app* androidApp;\nextern const ASensor* accelerometerSensor;\nextern ASensorEventQueue* sensorEventQueue;\n\nextern EGLDisplay androidDisplay;\nextern EGLSurface androidSurface;\nextern TheGame theGame;\n\nvoid mylog(const char* _Format, ...) {\n#ifdef _DEBUG\n char outStr[1024];\n va_list _ArgList;\n va_start(_ArgList, _Format);\n vsprintf(outStr, _Format, _ArgList);\n __android_log_print(ANDROID_LOG_INFO, "mylog", outStr, NULL);\n va_end(_ArgList);\n#endif\n};\n\nvoid mySwapBuffers() {\n\teglSwapBuffers(androidDisplay, androidSurface);\n}\nvoid myPollEvents() {\n\t\/\/ Read all pending events.\n\tint ident;\n\tint events;\n\tstruct android_poll_source* source;\n\n\t\/\/ If not animating, we will block forever waiting for events.\n\t\/\/ If animating, we loop until all events are read, then continue\n\t\/\/ to draw the next frame of animation.\n\twhile ((ident = ALooper_pollAll(0, NULL, &events,\n\t\t(void**)&source)) >= 0) {\n\n\t\t\/\/ Process this event.\n\t\tif (source != NULL) {\n\t\t\tsource->process(androidApp, source);\n\t\t}\n\n\t\t\/\/ If a sensor has data, process it now.\n\t\tif (ident == LOOPER_ID_USER) {\n\t\t\tif (accelerometerSensor != NULL) {\n\t\t\t\tASensorEvent event;\n\t\t\t\twhile (ASensorEventQueue_getEvents(sensorEventQueue,\n\t\t\t\t\t&event, 1) > 0) {\n\t\t\t\t\t\/\/LOGI("accelerometer: x=%f y=%f z=%f",\n\t\t\t\t\t\/\/\tevent.acceleration.x, event.acceleration.y,\n\t\t\t\t\t\/\/\tevent.acceleration.z);\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\t\/\/ Check if we are exiting.\n\t\tif (androidApp->destroyRequested != 0) {\n\t\t\ttheGame.bExitGame = true;\n\t\t\tbreak;\n\t\t}\n\t}\n\t\/\/check screen size\n\tEGLint w, h;\n\teglQuerySurface(androidDisplay, androidSurface, EGL_WIDTH, &w);\n\teglQuerySurface(androidDisplay, androidSurface, EGL_HEIGHT, &h);\n\ttheGame.onScreenResize(w, h);\n}\nint myFopen_s(FILE** pFile, const char* filePath, const char* mode) {\n\t*pFile = fopen(filePath, mode);\n\tif (*pFile == NULL) {\n\t\tmylog("ERROR: can't open file %s\\n", filePath);\n\t\treturn -1;\n\t}\n\treturn 1;\n}\nint myMkDir(const char* outPath) {\n\tstruct stat info;\n\tif (stat(outPath, &info) == 0)\n\t\treturn 0; \/\/exists already\n\tint status = mkdir(outPath, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);\n\tif (status == 0)\n\t\treturn 1; \/\/Successfully created\n\tmylog("ERROR creating, status=%d, errno: %s.\\n", status, std::strerror(errno));\n\treturn -1;\n}\nvoid myStrcpy_s(char* dst, int maxSize, const char* src) {\n\tstrcpy(dst, src);\n\t\/\/fill tail by zeros\n\tint strLen = strlen(dst);\n\tif (strLen < maxSize)\n\t\tfor (int i = strLen; i < maxSize; i++)\n\t\t\tdst[i] = 0;\n}\n\n<\/pre><\/div>\n\n\n
\n\n\n\n![](\"https:\/\/writingagame.com\/img\/b01\/c22\/02.jpg\")
<\/p>\n\n\n\n![](\"https:\/\/writingagame.com\/img\/b01\/c22\/03.jpg\")
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