Best way to rotate an image using SDL?

Question

I am building a game and the main character's arm will be following the mouse cursor, so it will be rotating quite frequently. What would be the best way to rotate it?

Answer 1

With SDL you have a few choices.

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1. Rotate all your sprites in advance (pre-render all possible rotations) and render them like you would any other sprite. This approach is fast but uses more memory and more sprites. As @Nick Wiggle pointed out, RotSprite is a great tool for generating sprite transformations.

2. Use something like SDL_gfx to do real-time rotation/zooming. (Not recommended, very slow)

3. Use SDL in OpenGL mode and render your sprites to primitives, applying a rotation to the primitives.

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Option 3 is probably your best bet because you gain all of the advantages of using OpenGL. It's really up to you how to want to do it. It's also a possibility that you can load your sprites, perform all rotation calculations with SDL_gfx and then save the rotated versions to an SDL_Surface in memory.

EDIT: In response to your comment I would recommend checking out Lazyfoo's SDL tutorials. Specifically, this one about rotation. There is also an OpenGl function, glRotatef, which can be useful in your case. A quick search brought back this little tidbit which could also be helpful.

Answer 2

SDL_RenderCopyEx()

has extra arguments for rotation, flipping, and the rotation center.