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varun_shrivastava

OpenGL OpenGL 2.0 fixed functionality pipeline

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Hi,

I have been learning OpenGL ES 2.0 since last year. Now i have started with OpenGL 2.0.
The difference between the two comes out to be availability of fixed functionality pipeline.

So my question is do we gain something by the use of fixed functionality pipeline or we can just go ahead and write our own shaders and do our stuff,
without considering fixed functionality. That is to say, fixed functionality provides built in uniforms within shaders and other stuff too, that we can take advantage of but not sure
will that really make a difference because we can do all that within shaders by specifying our own uniforms and attributes.

Thanks
Varun

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Hi,

I have been learning OpenGL ES 2.0 since last year. Now i have started with OpenGL 2.0.
The difference between the two comes out to be availability of fixed functionality pipeline.

So my question is do we gain something by the use of fixed functionality pipeline or we can just go ahead and write our own shaders and do our stuff,
without considering fixed functionality. That is to say, fixed functionality provides built in uniforms within shaders and other stuff too, that we can take advantage of but not sure
will that really make a difference because we can do all that within shaders by specifying our own uniforms and attributes.

Thanks
Varun


No, you don't gain anything, all fixed function stuff is done using shaders by the drivers on modern cards anyway. (You might be able to save some development time by using fixed functions though)

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[quote name='varuns' timestamp='1321509242' post='4884870']
Hi,

I have been learning OpenGL ES 2.0 since last year. Now i have started with OpenGL 2.0.
The difference between the two comes out to be availability of fixed functionality pipeline.

So my question is do we gain something by the use of fixed functionality pipeline or we can just go ahead and write our own shaders and do our stuff,
without considering fixed functionality. That is to say, fixed functionality provides built in uniforms within shaders and other stuff too, that we can take advantage of but not sure
will that really make a difference because we can do all that within shaders by specifying our own uniforms and attributes.

Thanks
Varun


No, you don't gain anything, all fixed function stuff is done using shaders by the drivers on modern cards anyway. (You might be able to save some development time by using fixed functions though)
[/quote]

Thanks for the reply.
One more que: There is a limit on the number of uniforms, attributes and varying's we can define in a shader. So though the number is large enough on modern cards, but for general information, will it reduce the number of variables we can define. ie TOTAL - (variables exposed by fixed functionality). And will these pre-defined variables will take up memory even if they are not being used?

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Predefined variables are just sugar.
They consume uniform just like your own uniforms. I suggest not to use predefined things. It makes moving up to GL 3 and 4 easier.

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OpenGL 3 and up doesn't support fixed function.

Fixed function and immediate mode is nice for debugging and early stages in development when you want to render a texture from an FBO from a previous rendering pass to the screen. I'm slowly transitioning to no fixed function in my engine so I can start using OpenGL 3 soon.

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OpenGL 3 and up doesn't support fixed function.

Fixed function and immediate mode is nice for debugging and early stages in development when you want to render a texture from an FBO from a previous rendering pass to the screen. I'm slowly transitioning to no fixed function in my engine so I can start using OpenGL 3 soon.


You can use fixed function in GL 3 and above. You would have to create a "compatible" context (Windows). It is my understanding that a lot of CAD and DCC programs need it.
However, the compatible context is not available on OS X.

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