CODEWITHSUNDEEP
iosopengl-es
user978838
user978838

Reputation: 31

OpenGL es zooming to a touchPoint (iOS)

So I'm using the GLPaint sample from the Apple dev docs and I'm curious as to how I could implement zooming the view to a point based on a single/double tap. I don't need the touch handling part, as I am familiar with that. It's more the actual zooming that I can't wrap my head around. I'm a noob when it comes to OpenGL so I definitely could use some OpenGL guru's help on this one!

Upvotes: 0

Views: 344

Answers (1)

datenwolf
datenwolf

Reputation: 162164

In the terms of GLPaint: You can't, sorry, at least not without substantially changing GLPaint.

OpenGL is a drawing API and if you change something, you must redraw the whole thing. GLPaint is a ridiculous bad tutorial as it accumulates the drawing operations on the view framebuffer. Zooming however requires a full redraw, which will loose the contents of the view framebuffer, thus the drawing. One could fix this, by drawing to an intermediate framebuffer object, used as texture on a quad that's zoomed.

Or build a list of strokes that's rerendered everytime the zoom changes.

Upvotes: 1

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