gl errors with occlusion queries

Sage

Posts: 1,199
Joined: 2004.10

Post: #1

Oct 12, 2005 — 05:27 AM

I'm using occlusion queries to modulate the brightness of the sun in my engine. It looks and works great. Now, for purposes of correctness, I use two occlusion queries, one to see how many fragments *would* pass ( drawn with color and depth buffers masked, and depth test turned off ) and the second drawn normally. I get a ratio of the two to modulate my glare.

I just ran my app under GL profiler to try to track down a bug elswhere and I see that I'm getting a GL_INVALID_OPERATION on my occlusion tests. The spec says:

Code:

The error INVALID_OPERATION is generated if GetQueryObjectivARB or

GetQueryObjectuivARB is called where <id> is not the name of a query

object.

The error INVALID_OPERATION is generated if GetQueryObjectivARB or

GetQueryObjectuivARB is called where <id> is the name of a currently

active query object.

The error INVALID_ENUM is generated if GetQueryObjectivARB or

GetQueryObjectuivARB is called where <pname> is not QUERY_RESULT_ARB

or QUERY_RESULT_AVAILABLE_ARB.

I have to assume one of these is my problem, but I'm not certain how to work around it. I was under the operation that any number of occlusion queries could be run simultaneously...

Here's my code:

Code:

void CelestialBody::displayHaloOcclusionQueryTest( void )

{

    Camera *camera = world()->activeCamera();

    if ( !camera ) return;

    /*

        The dot-product approaches 1.0 as the camera faces the body.

    */

    float d = camera->looking() * _dir,

          radius = sinf( _haloArcSize * DEG2RAD ) * camera->farPlane();

    /*

        No point going further if we're facing away

    */

    if ( d < EPSILON ) return;

    float size = d * d * radius,

          alpha = d;

    /*

        Read result from last frame's occlusion query.

        Then, perform a new occlusion query,

        and then draw our halo.

        Queries will be one frame old, but who's going to notice?

    */

    readOcclusionQueryResult();

    performOcclusionQuery();                    

    /*

        Use the result from the last occlusion query to

        modulate out halo.

    */

    alpha = clamp( _occlusionQueryResult * alpha, 0.0f, 1.0f );

    displayHalo( camera, size, alpha, false );        

}

void CelestialBody::performOcclusionQuery( void )

{

    Camera *camera = world()->activeCamera();

    float distance = camera->farPlane(),

          size = sinf( _arcSize * DEG2RAD ) * distance;

    vec3 pos( camera->position() + (_dir * distance )),

         up, right, down, left;

    camera->billboardVectors( up, right, down, left );

    right *= size;

    up *= size;

    left *= size;

    down *= size;

    vec3 ll( pos + left + down ),

         lr( pos + right + down ),

         ur( pos + right + up ),

         ul( pos + left + up );

    glActiveTextureARB( GL_TEXTURE0_ARB );

    glDisable( GL_TEXTURE_2D );

    glEnable( GL_BLEND );

    glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );    

    glColor4f( 0,0,0,1 );

    glColorMask( GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE );

    glDepthMask( GL_FALSE );

    /*

        Run first query to see how many fragments *would* pass.

        To do this turn off depth test.

    */

    glDisable( GL_DEPTH_TEST );

    glBeginQuery( GL_SAMPLES_PASSED, _queryIDs[0] );

    glBegin( GL_QUADS );

        glVertex3fv( ll.v );

        glVertex3fv( lr.v );

        glVertex3fv( ur.v );

        glVertex3fv( ul.v );        

    glEnd();

    glEndQuery( GL_SAMPLES_PASSED );

    /*

        Run second query to see how many fragments *did* pass,

        by turning depth test back on.

    */

    glEnable( GL_DEPTH_TEST );

    glBeginQuery( GL_SAMPLES_PASSED, _queryIDs[1] );

    glBegin( GL_QUADS );

        glVertex3fv( ll.v );

        glVertex3fv( lr.v );

        glVertex3fv( ur.v );

        glVertex3fv( ul.v );        

    glEnd();

    glEndQuery( GL_SAMPLES_PASSED );

    glEnable( GL_TEXTURE_2D );

    glColorMask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );    

}

void CelestialBody::readOcclusionQueryResult( void )

{

    GLint fragmentsThatShouldPass = 0, fragmentsThatDidPass = 0;

    // !!! GL_INVALID_OPERATION thrown here...

    glGetQueryObjectivARB( _queryIDs[0], GL_QUERY_RESULT, &fragmentsThatShouldPass );

    glGetQueryObjectivARB( _queryIDs[1], GL_QUERY_RESULT, &fragmentsThatDidPass );

    if ( fragmentsThatShouldPass == 0 ) _occlusionQueryResult = 0.0f;    

    else _occlusionQueryResult = (float) fragmentsThatDidPass / (float) fragmentsThatShouldPass;

}

I get the GL_INVALID_OPERATION in the last method above, on the line:

Code:

    // !!! GL_INVALID_OPERATION thrown here...

    glGetQueryObjectivARB( _queryIDs[0], GL_QUERY_RESULT, &fragmentsThatShouldPass );

And here's the code that creates the query objects:

Code:

void CelestialBody::setUseOcclusionQuery( bool oq )

{

    /*

        Determine if occlusion querying is available, and if

        it's real.

    */

    _occlusionQueryAvailable = GLEW_ARB_occlusion_query;

    if ( _occlusionQueryAvailable )

    {

        GLint queryCounterBits = 0;

        glGetQueryiv(GL_SAMPLES_PASSED, GL_QUERY_COUNTER_BITS, &queryCounterBits);

        if ( queryCounterBits == 0 )

        {

            _occlusionQueryAvailable = false;

        }

    }

    if ( !_occlusionQueryAvailable ) 

    {

        using namespace PANSICore;

        Logger::log( LogEntry::Debug, "CelestialBody::setUseOcclusionQuery",

                     "OcclusionQuery is not available, using ray testing." );

        oq = false;

    }

    if ( oq )

    {

        Ray_Delete( _ray );

        _ray = NULL;

        if ( !_queryIDs[0] )

        {

            glGenQueriesARB( 2, _queryIDs );

        }

        setRequiresStepping( false );

    }

    else

    {

        if ( !_ray )

        {

            _ray = new Ray( this );

        }

        if ( _queryIDs[0] )

        {

            glDeleteQueriesARB( 2, _queryIDs );

            _queryIDs[0] = 0;

            _queryIDs[1] = 0;

        }

        /*

            Need to be stepped to update the ray

        */

        setRequiresStepping( true );

    }

}

As far as I can tell, I'm doing the right thing. I've got two query objects, and I only run one at a time.

Any ideas?

TomorrowPlusX

Sage

Posts: 1,199
Joined: 2004.10

Post: #2

Oct 12, 2005 — 10:08 AM

UPDATE:

I changed my code which performs the query to check if the results are available ( as well as wether the query object names are valid ) and I still get the error, just now it's on the call to GL_QUERY_RESULT_AVAILABLE.

What's even more baffling is that if I tell Profiler to continue -- past the breaks on error -- once the first frame is done rendering it works fine.

Baffling!

Possibly Related Threads...

Thread:		Author	Replies:	Views:	Last Post
	2D Pixel Collision Detection using OCCLUSION	Elphaba	0	2,969	Jun 8, 2009 06:30 AM Last Post: Elphaba
	Occlusion query code failing on ATI 9600	TomorrowPlusX	4	4,709	Mar 10, 2007 08:52 AM Last Post: arekkusu
	Occlusion query failing for fogged occluders	TomorrowPlusX	12	5,604	Jan 8, 2006 05:03 PM Last Post: arekkusu
	Occlusion queries... SLOW.	TomorrowPlusX	8	4,035	Aug 19, 2005 07:05 AM Last Post: TomorrowPlusX