two questions

Justin Bradford justin at ukans.edu
Thu Jan 28 19:49:24 PST 1999


On Wed, 27 Jan 1999, Paul Lowe wrote:
> My other question is: is there a way to directly access the framebuffer
> memory? I'm talking about going beyond the SDL_UpdateRect(Surface, x, x,
> x, x) memory. I want to access the MIT mem itself. Is this possible?

Doesn't bypassing SDL kind of void the point of using SDL?
But regardless, you should be able to manipulate SDL's internal structures
directly, just bypassing the functions. I haven't looked at SDL source
yet, so I don't know how feasible this is. I would imagine it is possible,
you'd just have to make the code conditional on the environment (ie, check
to make sure you're using shared mem on X). Maybe some locking stuff, too.
But I have no doubt that it's possible write a bypass; just a question of
how hard.

> See, I think the problem is being encountered because I
> am taking a step beyond SDL and it's "simplicity" he he, no offense sam
> dude....but I needz da speed...my own "more versatile" framebuffer code
> is needed. Is this realistic? Does I need to write my own graphix
> subsystem..(I don't want to).

SDL just interfaces other graphics subsystems. If you want to bypass SDL
entirely, why use it? Just code straight to DirectX, GGI, DGA, or
whatever. 

> Anyone here know the fundamentals to sprite rotation. I don't have the
> math skills, but don't know where to start. I am currently in Algebra 2.

Matrix math. You probably need a trig textbook. 
Also, if you have access to old copies of Dr Dobbs Journal, look for
columns by Michael Abrash. His X-Sharp library covers some 3D basics,
including bitmaps (which requires sprite rotation, translation, and
scaling).

Justin Bradford
justin at ukans.edu





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