Difference between surface and texture (SDL / general)

cgraphicssdlsdl-2

Can anyone explain to me in simple words what is the difference between texture and surface? I saw it used in SDL2 as SDL_Surface and SDL_Texture. SDL_Textureis created from SDL_Surface which in turn is created from image/bitmap. Both are collection of pixels. But I do not see the main difference between them (has to do something with GPU?)

I tried to google it but all explanations I found were too complex to understand them without digging deeper into computer graphics stuff.

Best Answer

Basically your assumption "has to do something with GPU?" is right.

SDL_Surface is used in software rendering. With software rendering, as saloomi2012 correctly noticed, you are using regular RAM to store image data. Thus, in most cases you can access data buffer associated with surface directly, modifying its content, i.e. it is using CPU, hence the software name.

SDL_Texture on the other hand, is used in a hardware rendering, textures are stored in VRAM and you don't have access to it directly as with SDL_Surface. The rendering operations are accelerated by GPU, using, internally, either OpenGL or DirectX (available only on Windows) API, which in turn are using your video hardware, hence hardware rendering name.

Needless to say that hardware rendering is by orders of magnitude faster than software rendering and should be always be considered as primary option.

Related Solutions

C++ – the difference between #include and #include “filename”

In practice, the difference is in the location where the preprocessor searches for the included file.

For #include <filename> the preprocessor searches in an implementation dependent manner, normally in search directories pre-designated by the compiler/IDE. This method is normally used to include standard library header files.

For #include "filename" the preprocessor searches first in the same directory as the file containing the directive, and then follows the search path used for the #include <filename> form. This method is normally used to include programmer-defined header files.

A more complete description is available in the GCC documentation on search paths.

The difference between ++i and i++

++i will increment the value of i, and then return the incremented value.
```
 i = 1;
 j = ++i;
 (i is 2, j is 2)
```
i++ will increment the value of i, but return the original value that i held before being incremented.
```
 i = 1;
 j = i++;
 (i is 2, j is 1)
```

For a for loop, either works. ++i seems more common, perhaps because that is what is used in K&R.

In any case, follow the guideline "prefer ++i over i++" and you won't go wrong.

There's a couple of comments regarding the efficiency of ++i and i++. In any non-student-project compiler, there will be no performance difference. You can verify this by looking at the generated code, which will be identical.

The efficiency question is interesting... here's my attempt at an answer: Is there a performance difference between i++ and ++i in C?

As @OnFreund notes, it's different for a C++ object, since operator++() is a function and the compiler can't know to optimize away the creation of a temporary object to hold the intermediate value.

Best Answer

Related Solutions

C++ – the difference between #include and #include “filename”

The difference between ++i and i++

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