Windows Defender will complain, but that’s to be expected, since this is not an approved source of executable files.<\/p>\n\n\n\n
<\/p>\n\n\n\n
Now, back to the topic: Start Visual Studio and open CPP\/a996rr\/pw\/pw.sln<\/em> project.<\/p>\n\n\n\n Let’s say we want to grab and drag locomotive here:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n How program supposed to detect is mouse on the locomotive or not?<\/p>\n\n\n\n Well, the first thing that comes to mind is to check bounding box:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n Obviously, being inside the bounding box does not automatically mean hitting the object (as shown above).<\/p>\n\n\n\n Hitting the projection of original (source) bounding box – YES, that would work:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n However, checking such <\/em>arbitrarily oriented rectangle is a rather challenging and somewhat cumbersome task. Instead, I am calculating the longest axis projection (I called it “CHORDA”) and a radius R as the shorter axis bisected:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n So, now the task comes down to calculating the distance from the cursor to the chorda. If less than chorda’s R – then we are in.<\/p>\n\n\n\n <\/p>\n\n\n\n Even easier. Since they are 2D, don’t even need to pre-calculate “chords” or bounding boxes. If distance from cursor is less than button radius – then hit. Structure is much simpler than SceneSubj<\/em>, so they are organized in a separate class UISubj<\/em>. Still there is a set of interactivity-related functions common with SceneSubjs<\/em>, such as:<\/p>\n\n\n\n To make both 2D UISubjs <\/em>and 3D SceneSubjs <\/em>equally accessible in TouchScreen <\/em>class, this functionality is declared separately in a new ScreenSubj <\/em>class, a parent <\/strong>for both UISubj <\/em>and SceneSubj <\/em>classes.<\/p>\n\n\n\n <\/p>\n\n\n\n The challenge here is to figure out 3D point on the table corresponding to 2D cursor’s screen position. Solution is to build 3D line (ray) from camera to the table passing through screen cursor position. Implemented in TheTable::getCursorAncorPointTable()<\/em>.<\/p>\n\n\n\n Key steps:<\/p>\n\n\n\n Start Android Studio and open CPP\/a996rr\/pa<\/em> project.<\/p>\n\n\n\n The difference from Windows solution is how we read the input. Instead of mouse events, we will obviously use touch events. We don’t even need special listeners here. CPP\/p_android\/platform.cpp -> myPollEvents()<\/em> receives all the related events directly. Then we need to convert them to our TouchScreen::touchScreenEvents array, the rest is handled by the shared code described above.<\/p>\n\n\n\n <\/p>\n\n\n\n One issue that deserves special attention:<\/p>\n\n\n\n Of course, this solution heavily relies on touch events like AMOTION_EVENT_ACTION_DOWN<\/em> and AMOTION_EVENT_ACTION_UP<\/em> (finger on and out of screen). Don’t know who to blame: Android, GameActivity, Samsung (in my case) or whoever makes screens for them, but anyway: these key events are often missed. So, I added a special extra code to track this: CPP\/p_android\/platform.cpp -> myPollEvents()<\/em>, from line 178.<\/p>\n\n\n\n The idea is:<\/p>\n\n\n\n If we have some touch-screen events when assuming that we don’t have any fingers on screen, it means that we (device) overlooked AMOTION_EVENT_ACTION_DOWN<\/em>.<\/p>\n\n\n\n And vice-versa: we assuming that we DO have a finger on screen, but there are no any incoming events for a while. Means – perhaps AMOTION_EVENT_ACTION_UP<\/em> overlooked.<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Now we’ll try to implement game objects’ reaction on our own manual input (mouse for instance). The main part is how to determine which game object the mouse is pointing at. We’ll use the same approach as in previous chapter. Unlike in collision detection we’ll calculate object’s sizes\/position not in world X-Z plane, but in […]<\/p>\n","protected":false},"author":1,"featured_media":2412,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-2388","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cross-platform-3d"],"_links":{"self":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/2388","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=2388"}],"version-history":[{"count":41,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/2388\/revisions"}],"predecessor-version":[{"id":2772,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/posts\/2388\/revisions\/2772"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/media\/2412"}],"wp:attachment":[{"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/media?parent=2388"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/categories?post=2388"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/writingagame.com\/index.php\/wp-json\/wp\/v2\/tags?post=2388"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n\n\n\nCase 1: 3D objects on the screen<\/h2>\n\n\n\n
![](\"https:\/\/writingagame.com\/img\/b04\/c11\/01.jpg\")
<\/p>\n\n\n\n![](\"https:\/\/writingagame.com\/img\/b04\/c11\/02.jpg\")
<\/p>\n\n\n\n![](\"https:\/\/writingagame.com\/img\/b04\/c11\/03.jpg\")
<\/p>\n\n\n\n![](\"https:\/\/writingagame.com\/img\/b04\/c11\/04.jpg\")
<\/p>\n\n\n\nImplementation:<\/h2>\n\n\n\n
\n
\n\n\n\nCase 2: buttons (2D)<\/h2>\n\n\n\n
\n
\n\n\n\nCase 3: dragging background (a game table)<\/h2>\n\n\n\n
\n
\n\n\n\nAndroid<\/h2>\n\n\n\n
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