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glGetError() INVALID_OPERATION (1282)


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#1 Vincent_M   Members   -  Reputation: 711

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Posted 21 February 2013 - 06:43 PM

OpenGL doesn't appear to want to render any triangles to the screen anymore. It'll render lines for my models' bones and normals just fine, however, but no triangles...

 

I checked glGetError() and it comes back with 1282, and a quick google reveals that this could be caused by some driver issues, however, I'm not sure. I was experimenting with some render target code before I noticed the issue, but again, I am getting some things to show up onscreen. I'm not even sure if error 1282 is the cause of this issue either. I've also tried restarting my computer.

 

Any ideas?

 

 

EDIT: A quicker looks reveals that the triangles are appearing, it's just that everything is rendered pure-black. There's one mesh that doesn't appear black, however.


Edited by Vincent_M, 21 February 2013 - 06:45 PM.


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#2 BitMaster   Crossbones+   -  Reputation: 4233

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Posted 22 February 2013 - 02:20 AM

glGetError returns the current error state of the OpenGL state machine. After calling glGetError, the error state reverts to GL_NO_ERROR and it will remain so until an OpenGL function is called which sets an error state.

If you find an unexpected error state you need to find the function(s) that set it. At some point glGetError is GL_NO_ERROR right before a GL call but not afterwards. This function is not used correctly.

It's probably not a bad idea to have (as a bare minimum solution) something like assert(glGetError() == GL_NO_ERROR); after each GL call. That will immediately complain about error conditions in debug builds but compile down to nothing in release builds.

#3 Nercury   Crossbones+   -  Reputation: 770

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Posted 22 February 2013 - 04:45 AM

Disable texturing before drawing non-textured things? And enable it.

 

glDisable(TEXTURE_2D);

 

But I guess we need more info.


Edited by Nercury, 22 February 2013 - 04:47 AM.


#4 DDoS   Members   -  Reputation: 312

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Posted 22 February 2013 - 06:27 AM

most likely you forget to bind some necessary data to the current shader, pls post your code

render for debugging with glPolygonmode in wireframe, helps alot

(and dont use black as background color ;D )



#5 Vincent_M   Members   -  Reputation: 711

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Posted 22 February 2013 - 06:50 PM

I've got to admit that this was the first time I've actually used glGetError() to track stuff down, but once I realized it holds the last error, I kept running it through my initialization code until I found the method that does it. Calling glGetError() after each gl* call is expensive on OES implementations, so if I do that, I'll have to setup a bunch of #ifdef preprocessors so that I can run my builds w/o being bogged down.

 

As far as glDisable(GL_TEXTURE_2D), I've been checking that, but this where I think the issue could lie because I actually don't call commonly used glEnable/glDisable states directly. Instead, I have my own method that holds a synchronization variable to determine whether the state is already enabled before calling glEnable(), and vice-versa. This meant to cull unnecessary calls for OES builds. I think something could be wrong with glBindTexture because I modified one of my wrapper methods recently for that particular call. I'll also have to check glActiveTexture's wrapper function...

 

My models also don't use just textures directly, they use a Material object that is configured to work with the corresponding config of my uber shader built for that model to render. My Material class has some logic when uploading texture types that don't exist across each mesh in my model (uber shaders work at the per-model level for efficiency). So, if some parts of my model uses normal mapping, but others don't, instead of loading two shaders, I just load one with normal mapping, and for materials that don't have normal maps associated with it, it'll send a default 2x2 normal map. If I'm using diffuse maps, then they default meshes without ambient maps to a white texture.

 

These textured vertices aren't lit, however, and I know it's going through the lighting shader too, so I think it's some sort of GL state issues like you've all pointed out.



#6 __SKYe   Members   -  Reputation: 1071

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Posted 23 February 2013 - 08:20 PM

glGetError returns the current error state of the OpenGL state machine. After calling glGetError, the error state reverts to GL_NO_ERROR and it will remain so until an OpenGL function is called which sets an error state.

 

That is not entirely correct.

 

If you check http://www.opengl.org/sdk/docs/man/xhtml/glGetError.xml, you'll find that more than one error may be recorded by OpenGL, and that glGetError() should be called in a loop until GL_NO_ERROR is returned.



#7 Vincent_M   Members   -  Reputation: 711

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Posted 24 February 2013 - 12:09 AM

I've only had 1 OpenGL error at once, but I was thinking it acts more like a stack that'll show the most current out of a queue up to some defined max




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