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glDrawElements problems

OpenGL
Started by xwskx Jan 14, 2008 at 3:30 PM 8 replies 1.9k views
Original Post
xwskx
xwskx
I'm currently using the "glDrawElements" for my program and for some odd reason it blows up frequently with a read access error. I am currently using visual studio and everytime the error occurs, and i look at the stack trace its a memory address. When i check the data in the indexes and vertex pointer all of them are correct. What could be causing this? The glGetError returns 0. I'm totally lost; is there any opengl debugger available for visual studio? Any advice or insight will be greatly appreciated TIA.
CodeMunkie
CodeMunkie
Could be any number of things. Need code plzkthx.
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V-man
V-man
There is this one that's free
http://glintercept.nutty.org/

There is also gDebugger which is works differently and includes more things like performance analysis.

There are still others
xwskx
xwskx
Well here is the code, and its pretty simple.

void DrawQuads(struct DtedHeader *dted, int LOD){		int  x,y;	int  limit = dted->NumOfLatitude*dted->NumOfLongitude;	GLushort indices[121*2];	GLuint length;	glEnableClientState(GL_COLOR_ARRAY);	glEnableClientState(GL_VERTEX_ARRAY);	glVertexPointer(3, GL_FLOAT, sizeof(struct utmCoord),dted->DtedData);	glColorPointer(3, GL_UNSIGNED_BYTE, sizeof(struct RGBstruct),dted->ColorData);	for(y=0;y<dted->NumOfLongitude-1; y+=LOD)	{			length = 0;		for(x=0; x<limit; x+=dted->NumOfLongitude*LOD)		{				indices[length++] = x+y;			indices[length++] = x+y+LOD;		}		glDrawElements(GL_QUAD_STRIP,length,GL_UNSIGNED_SHORT,indices);		}		glDisableClientState(GL_VERTEX_ARRAY);	glDisableClientState(GL_COLOR_ARRAY);}
xwskx
xwskx
When i run the debug and see the dissembly the error seems to occur right after the "call dword ptr [__imp__glDrawElements@16 "
and the "cmp esi,esp" is what what is causing the trouble.
The address in the esi, is an invalid memory location. I got this far, but i don't know where to take it from here any ideas?

   951: 		glDrawElements(GL_QUAD_STRIP,length,GL_UNSIGNED_SHORT,indices);	0046F8DE 8B F4            mov         esi,esp 0046F8E0 8D 85 F4 FD FF FF lea         eax,[indices] 0046F8E6 50               push        eax  0046F8E7 68 03 14 00 00   push        1403h 0046F8EC 8B 8D E8 FD FF FF mov         ecx,dword ptr [length] 0046F8F2 51               push        ecx  0046F8F3 6A 08            push        8    0046F8F5 FF 15 D0 AF B8 00 call        dword ptr [__imp__glDrawElements@16 (0B8AFD0h)] 0046F8FB 3B F4            cmp         esi,esp 0046F8FD E8 2E 33 FF FF   call        @ILT+3115(__RTC_CheckEsp) (462C30h)
zedz
zedz
90% of the time the error is caused cause u have left some state on
eg set glDisableClientState( GL_TEXTURE_COORD ) for each texture unit, GL_NORMALs SECONDARDY_COLOR, GL_VERTEX etc

u wont see anything onscreen (but it shouldnt crash) then reenable them one at a time, so u trace which one is causing the problem
xwskx
xwskx
thanks zedz!

you were totally right i left the GL_TEXTURE_COORD_ARRAY on the previous function. it had multiple exit points and left without disabling it. i guess i learned the hard way why multiple exit points are bad.

thanks for the tip, i've been working on this problem forever. i think i'm going to go back and review my codes to prevent similar mistakes.
zedz
zedz
i wouldnt disable stuff afterward
what ild do is something similar to what i have

all drawing is handled by one function

if ( per_vertex_contains_what & VERTEXATTRIB_VERTEX )		g_rm.ogl.setVertexArrayOFFSET( vertAttribs[0].attrib_size, vertAttribs[0].attrib_format, 0, vertAttribs[0].attrib_offset );	else		g_rm.ogl.DisableVertexArray();	if ( per_vertex_contains_what & VERTEXATTRIB_NORMAL )		g_rm.ogl.setNormalArrayOFFSET( vertAttribs[2].attrib_format, 0, vertAttribs[2].attrib_offset );	else		g_rm.ogl.DisableNormalArray();	if ( per_vertex_contains_what & VERTEXATTRIB_COLOR )		g_rm.ogl.setColorArrayOFFSET( vertAttribs[3].attrib_size, vertAttribs[3].attrib_format, 0, vertAttribs[3].attrib_offset );	else		g_rm.ogl.DisableColorArray();	if ( per_vertex_contains_what & VERTEXATTRIB_TEXCOORD0 )		g_rm.ogl.setTexCoordArrayOFFSET( 0, vertAttribs[8].attrib_size, vertAttribs[8].attrib_format, 0, vertAttribs[8].attrib_offset );	else		g_rm.ogl.DisableTexCoordArray( 0 );		if ( per_vertex_contains_what & VERTEXATTRIB_TEXCOORD1 )		g_rm.ogl.setTexCoordArrayOFFSET( 1, vertAttribs[9].attrib_size, vertAttribs[9].attrib_format, 0, vertAttribs[9].attrib_offset );	else		g_rm.ogl.DisableTexCoordArray( 1 );etc


ie it will set all states automatically + optimally
V-man
V-man
This is my current way:

if (vertexFormat== VNT)
{
}
else if (vertexFormat== VNTT)
{
}
else if (vertexFormat== VTC)
{
}
else...
xwskx
xwskx
interesting, i'll give that a try.

thanks for the tip

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