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golgoth13

OpenGL How Open is OpenGL?

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Hi everyone,

I'm slowly moving to OpenGL 3.3 core and up and I’m wondering if we can take a look under OpenGL’s hood somehow? How glViewport is done for instance… bear in mind that I’m anticipating getting smack in the face for asking a really obvious question!

cheers,

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OpenGL isn't open-source, it's open-specification. That means (I can be wrong here), you don't have to pay any royalty fees to use OpenGL on your eg. embedded device. The closest thing to OpenGL source code is Mesa3D, which is open-source implementation of OpenGL http://www.mesa3d.org/

I don't know why would you like to see source code of these functions anyway. Everything there is to know about glViewport is in OpenGL documentation and specification http://www.opengl.org/sdk/docs/man/xhtml/glViewport.xml

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To add to i_luv_cplusplus' notes, OpenGl represents a specification for a driver layer connecting to the graphics hardware. It is up to the companies that run the hardware to produce the compliant drivers. So, NVidia and ATI aren't likely to be handing out the source to those drivers. Though, for linux, there are opensourced drivers for said hardware, as well as the afore mentioned mesa library.

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Quote:
don't know why would you like to see source code of these functions anyway


I’m fairly new to 3.3 and I definitely don’t want a be out of line here but why remove basic functionalities and force developers to do a makeover of what was already doing the job nicely? feels like a step back in a sense. I admit it, I find specs heavy to read and soporific, wouldn’t a step by step on how to migrate and replace OpenGL legacy be more appealing to developers?

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Well, first off, you CAN replicate the old "fixed function" pipeline just fine in OpenGL 3 using shaders. It maybe would have been nice to have them release some direct code to do just that. But the core of it is, most the fixed function pipeline was depricated because they didnt make sense in the face of shaders. For instance, the lighting calls only let you do per-vertex lighting. Now a days, everyone is doing per-pixel lighting with normal/paralax/shadow/specular maps.

Though I will admit, that I am a bit at odds with OpenGL not providing a math library like DirectX does. But the lack of the fixed function stuff shouldn't set you back, as the shader way of doing things is a lot more flexable. Take a look over here for a decent "getting started" that shows you a lot of those basic things like setting up your matricies.

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