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Is GLEW necessary to use shaders? [solved: NOT necessary]

Started by transistor09 Feb 8, 2010 at 1:30 PM 16 replies 9k views

Original Post

Feb 8, 2010 at 1:30 PM

I've been able to use shaders with GLEW but now I'm trying to wglGetProcAddress manually. It doesn't leave empty pointers but doesn't work either. I define the funtions


typedef GLuint (APIENTRY * PFNGLCREATESHADERPROC) (GLenum type);
PFNGLCREATESHADERPROC glCreateShader = NULL;

//later
glCreateShader = (PFNGLCREATESHADERPROC) wglGetProcAddress ("glCreateShader");
if (!glCreateShader) MessageBox (hwnd, TEXT("fail at glCreateShader"), L"ERROR", MB_OK | MB_ICONSTOP);

//finally
vert = glCreateShader (GL_VERTEX_SHADER);

Same with glShaderSource, glCompileShader, glCreateProgram, glAttachShader, glLinkProgram, glUseProgram. No warnings, no errors, no hangs, just the same old fixed function. So is GLEW (or any other lib for that matter) necessary or am I missing something? [Edited by - transistor09 on February 10, 2010 11:00:45 AM]

Aks9

Feb 8, 2010 at 1:51 PM

Of course that GLEW, GLEE, or similar libs are not necessary to get pointers to GL functions. To skip extensive post, I suggest you to take a look at Introduction to OpenGL 3.2 - Tutorial 01

transistor09

Feb 8, 2010 at 2:10 PM

My code seems to be doing the same damn thing; no cookie though.

FILE * sourceFile = fopen ("shaders/vert", "rb");fseek (sourceFile, 0, SEEK_END);unsigned long size = ftell (sourceFile);rewind (sourceFile);char * source = (char *) malloc (size + 1);size = fread (source, 1, sizeof (char), sourceFile);source[size] = 0;vert = glCreateShader (GL_VERTEX_SHADER);glShaderSource (vert, 1, (const char **) &source, NULL);glCompileShader (vert);sourceFile = freopen ("shaders/frag", "rb", sourceFile);fseek (sourceFile, 0, SEEK_END);size = ftell (sourceFile);rewind (sourceFile);source = (char *) realloc (source, size + 1);size = fread (source, sizeof (char), size, sourceFile);source[size] = 0;frag = glCreateShader (GL_FRAGMENT_SHADER);glShaderSource (frag, 1, (const char **) &source, NULL);glCompileShader (frag);fclose (sourceFile);free (source);prog = glCreateProgram ();glAttachShader (prog, vert);glAttachShader (prog, frag);glLinkProgram (prog);GLint linked;glGetProgramiv (prog, GL_LINK_STATUS, &linked);if (linked) MessageBox (hwnd, TEXT("program liked"), L"message", MB_OK | MB_ICONSTOP);

I get no "program liked" message

swiftcoder

Feb 8, 2010 at 2:34 PM

Quote:
Original post by transistor09
So is GLEW (or any other lib for that matter) necessary or am I missing something?

GLee/GLEW are not in any way necessary, but they exist to make your life easier. Unless you are working on a 4k intro, I see little point in putting yourself through the hell that is the OpenGL extensions mechanism.

transistor09

Feb 8, 2010 at 2:38 PM

Quote:
Original post by swiftcoder
[...] Unless you are working on a 4k intro, I see little point in putting yourself through the hell that is the OpenGL extensions mechanism.

Is it really that hard?

I just don't know which lib is the best so I'm trying to do with no lib at all

swiftcoder

Feb 8, 2010 at 2:57 PM

Quote:
Original post by transistor09
Quote:
Original post by swiftcoder
[...] Unless you are working on a 4k intro, I see little point in putting yourself through the hell that is the OpenGL extensions mechanism.
Is it really that hard?

It isn't hard at all - it is just pages and pages of boilerplate code that someone else has already written for you.

Quote:
I just don't know which lib is the best so I'm trying to do with no lib at all

Take this argument to its conclusion, and you will wind up implementing your own OS because "I don't know whether Windows or Mac is better" [smile]

transistor09

Feb 8, 2010 at 3:09 PM

Yeah, I'm not a guy that likes high-level too much. Despite that, have anything to recommend, swiftcoder?

V-man

Feb 8, 2010 at 3:41 PM

I like GLEW. It makes my program run 5 times faster. You have to call glewInit.

swiftcoder

Feb 8, 2010 at 4:29 PM

Quote:
Original post by transistor09
Despite that, have anything to recommend, swiftcoder?

I never tried GLEW - GLee was simpler to install on a Mac back when I discovered it, so that is what I have used ever since. It is about zero hassle - compile it in or link to it, and include GLee.h instead of GL.h.

Cromulent

Feb 8, 2010 at 6:45 PM

Quote:
Original post by swiftcoder
Quote:
Original post by transistor09
Despite that, have anything to recommend, swiftcoder?
I never tried GLEW - GLee was simpler to install on a Mac back when I discovered it, so that is what I have used ever since. It is about zero hassle - compile it in or link to it, and include GLee.h instead of GL.h.

Just as a little aside, GLEW is now incredibly easy on the Mac. Download, run Make, put in /usr/local/lib and /usr/local/include respectively.

No fuss.

idinev

Feb 8, 2010 at 7:00 PM

http://www.gamedev.net/community/forums/topic.asp?topic_id=557319&whichpage=1&#3579464

transistor09

Feb 9, 2010 at 5:38 AM

Oh, OK. Gonna stick with the GLEW; thanks everyone!

transistor09

Feb 9, 2010 at 10:47 AM

Umm, scratch that, there was an error (you can clearly see it in my posted code) in my file loader. Everything works fine without GLEW.

For me, binding extensions is easier than converting a VC6 project to work with CodeBlocks.

maxgpgpu

Feb 10, 2010 at 4:27 AM

Quote:
Original post by V-manI like GLEW. It makes my program run 5 times faster. You have to call glewInit.

Please tell me that's a joke. On the small chance you're serious... why so? Also, do you need to call the glewInit() function if you compile the GLEW files into your program (and thus not link it in)?

transistor09

Feb 10, 2010 at 7:28 AM

Quote:
Also, do you need to call the glewInit() function if you compile the GLEW files into your program (and thus not link it in)?

Yes. I bet its the function that GLEW uses to bind extensions. If you try to use any function before glewInit(), the program fails. [GL]Extensions are done differently than linking. You have to manually initialize the function pointer to it's prototype.

swiftcoder

Feb 10, 2010 at 7:54 AM

Quote:
Original post by transistor09
Quote:
Also, do you need to call the glewInit() function if you compile the GLEW files into your program (and thus not link it in)?

Yes. I bet its the function that GLEW uses to bind extensions. If you try to use any function before glewInit(), the program fails. [GL]Extensions are done differently than linking. You have to manually initialize the function pointer to it's prototype.

Correct. However, GLee handles this under the hood (unlike GLEW).

V-man

Feb 10, 2010 at 11:56 AM

Quote:
Original post by maxgpgpu
Quote:
Original post by V-manI like GLEW. It makes my program run 5 times faster. You have to call glewInit.
Please tell me that's a joke. On the small chance you're serious... why so? Also, do you need to call the glewInit() function if you compile the GLEW files into your program (and thus not link it in)?

It was a joke. This thread seems kind of too boring for my taste.
Anyway, GLEW is the best.
GLEE, every time you call a gl function, GLEE checks to see if it has initialized. It might not have an effect on performance, but I prefer GLEW's way.

Have fun with GL!

transistor09

Feb 10, 2010 at 12:27 PM

Quote:
Original post by V-manThis thread seems kind of too boring for my taste.

Better than homework assignment solution request or illegible Engrish.

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