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How to ZoomIn/ZoomOut of a 2D world while keeping the clicked point visible?
Author
Hello,
How can I ZoomIn/ZoomOut in a 2D world (I am using orthographic projection) so that the clicked point (or the point that initiated the zoom always remains visible). e.g.
If you want a given point on-screen to remain in the same place, relative to the screen, after a zoom change, what you want to do is find the world and on-screen positions of you want to track, make the zoom change, find the new world coordinate of the same on-screen position, and then move the view by the difference between the two world coordinates.
A source snippet from the event loop of my home-grown CAD application; getMouseLoc() calls glfwGetMousePos(&x, &y) and returns the 2D world coordinate under the cursor. A 3-dimension vector Float3 is used only because I didn't want to maintain multiple vector classes.
A source snippet from the event loop of my home-grown CAD application; getMouseLoc() calls glfwGetMousePos(&x, &y) and returns the 2D world coordinate under the cursor. A 3-dimension vector Float3 is used only because I didn't want to maintain multiple vector classes.
// Zoom in or out with wheel movement. int mouseWheel = glfwGetMouseWheel(); int mouseSign = sign(mouseWheel); if ( mouseWheel != 0 ) { Float3 preZoomCursor = getMouseLoc(); float preZoom = zoom; zoom += log10(zoom) * 5 * mouseSign; if ( zoom < 2 ) zoom = 2; glfwSetMouseWheel(0); // Maintain focus only when zooming in. Remove the 'if' to // lock the focus position when zooming out as well, but this // looks unintuitive to most people; it ends up zooming out and // away from the focus point. if ( zoom > preZoom ) { cameraLoc += preZoomCursor - getMouseLoc(); } }This topic is closed to new replies.
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