Re: please post GLSL software rendering example

Subject: Re: please post GLSL software rendering example

From: Geoff Stahl <email@hidden>

Date: Tue, 17 May 2005 16:34:11 -0700

Delivered-to: email@hidden

The resources pointed to by others are very valuable. The bottom line is this is simply a renderer selection in your pixel format attribs. You may want to also check the extensions string (a good habit to have). These code snippets should be helpful.

CGL:

This is a simple GLSL init routine I use for tests...

int glInit (void)

{

SInt32 osVersion = 0;

int validEnvironment = 1;

CGLPixelFormatAttribute attribs[] = { kCGLPFADisplayMask,

CGDisplayIDToOpenGLDisplayMask(CGMainDisplayID()),

kCGLPFARendererID, kCGLRendererGenericFloatID, /* floating point software renderer */

0 };

CGLPixelFormatObj pixelFormat = NULL;

long numPixelFormats = 0;

CGLChoosePixelFormat (attribs, &pixelFormat, &numPixelFormats);

if (pixelFormat) {

CGLCreateContext(pixelFormat, NULL, &cglContext);

CGLDestroyPixelFormat (pixelFormat);

CGLSetCurrentContext (cglContext);

/* must have these 4 extensions for GLSL support */

if (!gluCheckExtension("GL_ARB_shader_objects", glGetString (GL_EXTENSIONS)) ||

!gluCheckExtension("GL_ARB_vertex_shader", glGetString (GL_EXTENSIONS)) ||

!gluCheckExtension("GL_ARB_fragment_shader", glGetString (GL_EXTENSIONS)) ||

!gluCheckExtension("GL_ARB_shading_language_100", glGetString (GL_EXTENSIONS)))

validEnvironment = 0;

}

if (Gestalt(gestaltSystemVersion, &osVersion) == noErr)

printf ("system: Mac OS X v10.%ld.%ld\n", (osVersion - 0x1000) / 0x10, (osVersion - 0x1000) % 0x10);

return validEnvironment;

}

void glDispose (void)

{

CGLDestroyContext (cglContext);

}

Cocoa:

You need a pixel format for the float renderer:

// pixel format definition

+ (NSOpenGLPixelFormat*) floatPixelFormat

{

NSOpenGLPixelFormatAttribute attributes [] = {

NSOpenGLPFAWindow,

NSOpenGLPFADoubleBuffer, // double buffered

NSOpenGLPFADepthSize, (NSOpenGLPixelFormatAttribute)32, // 32 bit depth buffer

NSOpenGLPFARendererID, kCGLRendererGenericFloatID, // software renderer

(NSOpenGLPixelFormatAttribute)nil

};

return [[[NSOpenGLPixelFormat alloc] initWithAttributes:attributes] autorelease];

}

and a context:

[[NSOpenGLContext alloc] initWithFormat: [GLSLView floatPixelFormat] shareContext:nil]

Carbon: (something like...)

GLint attrib[] = { AGL_RGBA, AGL_DOUBLEBUFFER, AGL_DEPTH_SIZE, 32,

AGL_RENDERER_ID, AGL_RENDERER_GENERIC_FLOAT_ID, AGL_NONE };

aglPixFmt = aglChoosePixelFormat(NULL, 0, attrib);

if (aglPixFmt)

aglContext = aglCreateContext(aglPixFmt, NULL);

if (aglContext) {

aglSetDrawable(aglContext, GetWindowPort (window));

aglSetCurrentContext(pContextInfo->aglContext);

}

Geoff Stahl
3D Software Engineer
Apple

On May 17, 2005, at 4:02 PM, email@hidden wrote:

Fellow Mac developers,

I understand it's possible to use the floating-point
software renderer to run GLSL projects. For the purpose
of learning GLSL, that's probably good enough. It seems
that the only way to create a windowed drawable area for
GLSL is by using AGL. Unfortunately, I don't know AGL and
the documentation in the ADC Reference Library is no good
as a tutorial. I couldn't find any tutorials on the Internet
either. Could somebody please post source code snippets, or
a packaged Xcode project, demonstrating the creation of a
GLSL-capable OpenGL context and drawable area.

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